1
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Podkowik M, Perault AI, Putzel G, Pountain A, Kim J, DuMont AL, Zwack EE, Ulrich RJ, Karagounis TK, Zhou C, Haag AF, Shenderovich J, Wasserman GA, Kwon J, Chen J, Richardson AR, Weiser JN, Nowosad CR, Lun DS, Parker D, Pironti A, Zhao X, Drlica K, Yanai I, Torres VJ, Shopsin B. Quorum-sensing agr system of Staphylococcus aureus primes gene expression for protection from lethal oxidative stress. eLife 2024; 12:RP89098. [PMID: 38687677 PMCID: PMC11060713 DOI: 10.7554/elife.89098] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/02/2024] Open
Abstract
The agr quorum-sensing system links Staphylococcus aureus metabolism to virulence, in part by increasing bacterial survival during exposure to lethal concentrations of H2O2, a crucial host defense against S. aureus. We now report that protection by agr surprisingly extends beyond post-exponential growth to the exit from stationary phase when the agr system is no longer turned on. Thus, agr can be considered a constitutive protective factor. Deletion of agr resulted in decreased ATP levels and growth, despite increased rates of respiration or fermentation at appropriate oxygen tensions, suggesting that Δagr cells undergo a shift towards a hyperactive metabolic state in response to diminished metabolic efficiency. As expected from increased respiratory gene expression, reactive oxygen species (ROS) accumulated more in the agr mutant than in wild-type cells, thereby explaining elevated susceptibility of Δagr strains to lethal H2O2 doses. Increased survival of wild-type agr cells during H2O2 exposure required sodA, which detoxifies superoxide. Additionally, pretreatment of S. aureus with respiration-reducing menadione protected Δagr cells from killing by H2O2. Thus, genetic deletion and pharmacologic experiments indicate that agr helps control endogenous ROS, thereby providing resilience against exogenous ROS. The long-lived 'memory' of agr-mediated protection, which is uncoupled from agr activation kinetics, increased hematogenous dissemination to certain tissues during sepsis in ROS-producing, wild-type mice but not ROS-deficient (Cybb-/-) mice. These results demonstrate the importance of protection that anticipates impending ROS-mediated immune attack. The ubiquity of quorum sensing suggests that it protects many bacterial species from oxidative damage.
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Affiliation(s)
- Magdalena Podkowik
- Department of Medicine, Division of Infectious Diseases, NYU Grossman School of MedicineNew YorkUnited States
- Antimicrobial-Resistant Pathogens Program, New York University School of MedicineNew YorkUnited States
| | - Andrew I Perault
- Antimicrobial-Resistant Pathogens Program, New York University School of MedicineNew YorkUnited States
- Department of Microbiology, NYU Grossman School of MedicineNew YorkUnited States
| | - Gregory Putzel
- Antimicrobial-Resistant Pathogens Program, New York University School of MedicineNew YorkUnited States
- Department of Microbiology, NYU Grossman School of MedicineNew YorkUnited States
- Microbial Computational Genomic Core Lab, NYU Grossman School of MedicineNew YorkUnited States
| | - Andrew Pountain
- Institute for Systems Genetics; NYU Grossman School of MedicineNew YorkUnited States
| | - Jisun Kim
- Department of Pathology, Immunology and Laboratory Medicine, Center for Immunity and Inflammation, Rutgers New Jersey Medical SchoolNewarkUnited States
| | - Ashley L DuMont
- Department of Medicine, Division of Infectious Diseases, NYU Grossman School of MedicineNew YorkUnited States
| | - Erin E Zwack
- Department of Microbiology, NYU Grossman School of MedicineNew YorkUnited States
| | - Robert J Ulrich
- Department of Medicine, Division of Infectious Diseases, NYU Grossman School of MedicineNew YorkUnited States
| | - Theodora K Karagounis
- Antimicrobial-Resistant Pathogens Program, New York University School of MedicineNew YorkUnited States
- Ronald O. Perelman Department of Dermatology; NYU Grossman School of MedicineNew YorkUnited States
| | - Chunyi Zhou
- Department of Medicine, Division of Infectious Diseases, NYU Grossman School of MedicineNew YorkUnited States
- Antimicrobial-Resistant Pathogens Program, New York University School of MedicineNew YorkUnited States
| | - Andreas F Haag
- School of Medicine, University of St AndrewsSt AndrewsUnited Kingdom
| | - Julia Shenderovich
- Antimicrobial-Resistant Pathogens Program, New York University School of MedicineNew YorkUnited States
- Department of Microbiology, NYU Grossman School of MedicineNew YorkUnited States
| | - Gregory A Wasserman
- Department of Surgery, Northwell Health Lenox Hill HospitalNew YorkUnited States
| | - Junbeom Kwon
- Department of Medicine, Division of Infectious Diseases, NYU Grossman School of MedicineNew YorkUnited States
| | - John Chen
- Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of SingaporeSingaporeSingapore
| | - Anthony R Richardson
- Department of Microbiology and Molecular Genetics, University of PittsburghPittsburghUnited States
| | - Jeffrey N Weiser
- Department of Microbiology, NYU Grossman School of MedicineNew YorkUnited States
| | - Carla R Nowosad
- Department of Pathology, NYU Grossman School of MedicineNew YorkUnited States
| | - Desmond S Lun
- Center for Computational and Integrative Biology and Department of Computer Science, Rutgers UniversityCamdenUnited States
| | - Dane Parker
- Department of Pathology, Immunology and Laboratory Medicine, Center for Immunity and Inflammation, Rutgers New Jersey Medical SchoolNewarkUnited States
| | - Alejandro Pironti
- Antimicrobial-Resistant Pathogens Program, New York University School of MedicineNew YorkUnited States
- Department of Microbiology, NYU Grossman School of MedicineNew YorkUnited States
- Microbial Computational Genomic Core Lab, NYU Grossman School of MedicineNew YorkUnited States
| | - Xilin Zhao
- State Key Laboratory of Molecular Vaccinology and Molecular Diagnostics, School of Public Health, Xiamen UniversityXiamenChina
| | - Karl Drlica
- Public Health Research Institute, New Jersey Medical School, Rutgers UniversityNew YprkUnited States
- Department of Microbiology, Biochemistry & Molecular Genetics, New Jersey Medical School, Rutgers UniversityNewarkUnited States
| | - Itai Yanai
- Institute for Systems Genetics; NYU Grossman School of MedicineNew YorkUnited States
- Department of Biochemistry and Molecular Pharmacology, NYU Grossman School of MedicineNew YorkUnited States
| | - Victor J Torres
- Antimicrobial-Resistant Pathogens Program, New York University School of MedicineNew YorkUnited States
- Department of Microbiology, NYU Grossman School of MedicineNew YorkUnited States
| | - Bo Shopsin
- Department of Medicine, Division of Infectious Diseases, NYU Grossman School of MedicineNew YorkUnited States
- Antimicrobial-Resistant Pathogens Program, New York University School of MedicineNew YorkUnited States
- Department of Microbiology, NYU Grossman School of MedicineNew YorkUnited States
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2
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Podkowik M, Perault AI, Putzel G, Pountain A, Kim J, Dumont A, Zwack E, Ulrich RJ, Karagounis TK, Zhou C, Haag AF, Shenderovich J, Wasserman GA, Kwon J, Chen J, Richardson AR, Weiser JN, Nowosad CR, Lun DS, Parker D, Pironti A, Zhao X, Drlica K, Yanai I, Torres VJ, Shopsin B. Quorum-sensing agr system of Staphylococcus aureus primes gene expression for protection from lethal oxidative stress. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.06.08.544038. [PMID: 37333372 PMCID: PMC10274873 DOI: 10.1101/2023.06.08.544038] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/20/2023]
Abstract
The agr quorum-sensing system links Staphylococcus aureus metabolism to virulence, in part by increasing bacterial survival during exposure to lethal concentrations of H2O2, a crucial host defense against S. aureus. We now report that protection by agr surprisingly extends beyond post-exponential growth to the exit from stationary phase when the agr system is no longer turned on. Thus, agr can be considered a constitutive protective factor. Deletion of agr increased both respiration and fermentation but decreased ATP levels and growth, suggesting that Δagr cells assume a hyperactive metabolic state in response to reduced metabolic efficiency. As expected from increased respiratory gene expression, reactive oxygen species (ROS) accumulated more in the agr mutant than in wild-type cells, thereby explaining elevated susceptibility of Δagr strains to lethal H2O2 doses. Increased survival of wild-type agr cells during H2O2 exposure required sodA, which detoxifies superoxide. Additionally, pretreatment of S. aureus with respiration-reducing menadione protected Δagr cells from killing by H2O2. Thus, genetic deletion and pharmacologic experiments indicate that agr helps control endogenous ROS, thereby providing resilience against exogenous ROS. The long-lived "memory" of agr-mediated protection, which is uncoupled from agr activation kinetics, increased hematogenous dissemination to certain tissues during sepsis in ROS-producing, wild-type mice but not ROS-deficient (Nox2-/-) mice. These results demonstrate the importance of protection that anticipates impending ROS-mediated immune attack. The ubiquity of quorum sensing suggests that it protects many bacterial species from oxidative damage.
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Affiliation(s)
- Magdalena Podkowik
- Department of Medicine, Division of Infectious Diseases, NYU Grossman School of Medicine, New York, NY, USA
- Antimicrobial-Resistant Pathogens Program, New York University School of Medicine, New York, NY, USA
| | - Andrew I. Perault
- Antimicrobial-Resistant Pathogens Program, New York University School of Medicine, New York, NY, USA
- Department of Microbiology, NYU Grossman School of Medicine, New York, NY, USA
| | - Gregory Putzel
- Antimicrobial-Resistant Pathogens Program, New York University School of Medicine, New York, NY, USA
- Department of Microbiology, NYU Grossman School of Medicine, New York, NY, USA
- Microbial Computational Genomic Core Lab, NYU Grossman School of Medicine, New York, NY, USA
| | - Andrew Pountain
- Institute for Systems Genetics; NYU Grossman School of Medicine, New York, NY, USA
| | - Jisun Kim
- Department of Pathology, Immunology and Laboratory Medicine, Center for Immunity and Inflammation, Rutgers New Jersey Medical School Cancer Center, Newark, NJ, USA
| | - Ashley Dumont
- Department of Microbiology, NYU Grossman School of Medicine, New York, NY, USA
| | - Erin Zwack
- Department of Microbiology, NYU Grossman School of Medicine, New York, NY, USA
| | - Robert J. Ulrich
- Department of Medicine, Division of Infectious Diseases, NYU Grossman School of Medicine, New York, NY, USA
| | - Theodora K. Karagounis
- Antimicrobial-Resistant Pathogens Program, New York University School of Medicine, New York, NY, USA
- Ronald O. Perelman Department of Dermatology; NYU Grossman School of Medicine, New York, NY, USA
| | - Chunyi Zhou
- Department of Medicine, Division of Infectious Diseases, NYU Grossman School of Medicine, New York, NY, USA
- Antimicrobial-Resistant Pathogens Program, New York University School of Medicine, New York, NY, USA
| | - Andreas F. Haag
- School of Medicine, University of St Andrews, St Andrews, UK
| | - Julia Shenderovich
- Antimicrobial-Resistant Pathogens Program, New York University School of Medicine, New York, NY, USA
- Department of Microbiology, NYU Grossman School of Medicine, New York, NY, USA
| | | | - Junbeom Kwon
- Department of Medicine, Division of Infectious Diseases, NYU Grossman School of Medicine, New York, NY, USA
| | - John Chen
- Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | - Anthony R. Richardson
- Department of Microbiology and Molecular Genetics, University of Pittsburgh, Pittsburgh, PA, USA
| | - Jeffrey N. Weiser
- Department of Microbiology, NYU Grossman School of Medicine, New York, NY, USA
| | - Carla R. Nowosad
- Department of Pathology, NYU Grossman School of Medicine, New York, NY, USA
| | - Desmond S. Lun
- Center for Computational and Integrative Biology and Department of Computer Science, Rutgers University, Camden, NJ, USA
| | - Dane Parker
- Department of Pathology, Immunology and Laboratory Medicine, Center for Immunity and Inflammation, Rutgers New Jersey Medical School Cancer Center, Newark, NJ, USA
| | - Alejandro Pironti
- Antimicrobial-Resistant Pathogens Program, New York University School of Medicine, New York, NY, USA
- Department of Microbiology, NYU Grossman School of Medicine, New York, NY, USA
- Microbial Computational Genomic Core Lab, NYU Grossman School of Medicine, New York, NY, USA
| | - Xilin Zhao
- State Key Laboratory of Molecular Vaccinology and Molecular Diagnostics, School of Public Health, Xiamen University, Xiamen, Fujian Province, China
| | - Karl Drlica
- Public Health Research Institute, New Jersey Medical School, Rutgers University, Newark, NJ, USA
- Department of Microbiology, Biochemistry & Molecular Genetics, New Jersey Medical School, Rutgers University, Newark, NJ, USA
| | - Itai Yanai
- Institute for Systems Genetics; NYU Grossman School of Medicine, New York, NY, USA
- Department of Biochemistry and Molecular Pharmacology, NYU Grossman School of Medicine, New York, NY, USA
| | - Victor J. Torres
- Antimicrobial-Resistant Pathogens Program, New York University School of Medicine, New York, NY, USA
- Department of Microbiology, NYU Grossman School of Medicine, New York, NY, USA
| | - Bo Shopsin
- Department of Medicine, Division of Infectious Diseases, NYU Grossman School of Medicine, New York, NY, USA
- Antimicrobial-Resistant Pathogens Program, New York University School of Medicine, New York, NY, USA
- Department of Microbiology, NYU Grossman School of Medicine, New York, NY, USA
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3
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Anderson EE, Ilmain JK, Torres VJ. SarS and Rot are necessary for the repression of lukED and lukSF-PV in Staphylococcus aureus. Microbiol Spectr 2023; 11:e0165623. [PMID: 37800956 PMCID: PMC10715151 DOI: 10.1128/spectrum.01656-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2023] [Accepted: 08/21/2023] [Indexed: 10/07/2023] Open
Abstract
IMPORTANCE The leukocidins play an important role in disarming the host immune system and promoting infection. While both SarS and Rot have been established as repressors of leukocidins, the importance of each repressor in infection is unclear. Here, we demonstrate that repression by SarS and Rot is not additive and show that in addition to upregulating expression of each other, they are also able to bind concurrently to the leukocidin promoters. These findings suggest that both repressors are necessary for maximal repression of lukED and lukSF-PV and illuminate another complex relationship among Staphylococcus aureus virulence regulators.
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Affiliation(s)
- Exene E. Anderson
- Department of Microbiology, New York University Grossman School of Medicine, New York, New York, USA
| | - Juliana K. Ilmain
- Department of Microbiology, New York University Grossman School of Medicine, New York, New York, USA
| | - Victor J. Torres
- Department of Microbiology, New York University Grossman School of Medicine, New York, New York, USA
- Department of Host-Microbe Interactions, St. Jude Children’s Research Hospital, Memphis, Tennessee, USA
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4
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Tao Z, Wang H, Ke K, Shi D, Zhu L. Flavone inhibits Staphylococcus aureus virulence via inhibiting the sae two component system. Microb Pathog 2023; 180:106128. [PMID: 37148922 DOI: 10.1016/j.micpath.2023.106128] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2023] [Revised: 04/08/2023] [Accepted: 04/26/2023] [Indexed: 05/08/2023]
Abstract
The rising prevalence of antibiotic resistance in Staphylococcus aureus calls for the development of innovative antimicrobial agents targeting novel pathways. S. aureus generates various virulence factors that compromise host defense mechanisms. Flavone, a core structure of flavonoids, has been shown to diminish the production of staphyloxanthin and alpha-hemolysin. Nonetheless, the influence of flavone on the majority of other virulence factors in S. aureus and its underlying molecular mechanism remain elusive. In this study, we examined the impact of flavone on the transcriptional profile of S. aureus using transcriptome sequencing. Our findings revealed that flavone substantially downregulated the expression of over 30 virulence factors implicated in immune evasion by the pathogen. Gene set enrichment analysis of the fold change-ranked gene list in relation to the Sae regulon indicated a robust association between flavone-induced downregulation and membership in the Sae regulon. Through the analysis of Sae target promoter-gfp fusion expression patterns, we observed a dose-dependent inhibition of Sae target promoter activity by flavone. Moreover, we discovered that flavone protected human neutrophils from S. aureus-mediated killing. Flavone also decreased the expression of alpha-hemolysin and other hemolytic toxins, resulting in a reduction in S. aureus' hemolytic capacity. Additionally, our data suggested that the inhibitory effect of flavone on the Sae system operates independently of its capacity to lower staphyloxanthin levels. In conclusion, our study proposes that flavone exhibits a broad inhibitory action on multiple virulence factors of S. aureus by targeting the Sae system, consequently diminishing the bacterium's pathogenicity.
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Affiliation(s)
- Zhanhua Tao
- Institute of Eco-Environmental Research, Guangxi Academy of Sciences, Nanning, 530003, Guangxi, China; Guangxi Key Laboratory of Marine Natural Products and Combinatorial Biosynthesis Chemistry, Nanning, 530003, Guangxi, China.
| | - Haoren Wang
- The First Affiliated Hospital of Jiamusi University, Jiamusi, 154002, Heilongjiang, China.
| | - Ke Ke
- Guangxi Academy of Sciences, Nanning, 530003, Guangxi, China.
| | - Deqiang Shi
- Guangxi Academy of Sciences, Nanning, 530003, Guangxi, China.
| | - Libo Zhu
- Guangxi Academy of Sciences, Nanning, 530003, Guangxi, China.
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5
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Anderson EE, Dyzenhaus S, Ilmain JK, Sullivan MJ, van Bakel H, Torres VJ. SarS Is a Repressor of Staphylococcus aureus Bicomponent Pore-Forming Leukocidins. Infect Immun 2023; 91:e0053222. [PMID: 36939325 PMCID: PMC10112191 DOI: 10.1128/iai.00532-22] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2022] [Accepted: 02/20/2023] [Indexed: 03/21/2023] Open
Abstract
Staphylococcus aureus is a successful pathogen that produces a wide range of virulence factors that it uses to subvert and suppress the immune system. These include the bicomponent pore-forming leukocidins. How the expression of these toxins is regulated is not completely understood. Here, we describe a screen to identify transcription factors involved in the regulation of leukocidins. The most prominent discovery from this screen is that SarS, a known transcription factor which had previously been described as a repressor of alpha-toxin expression, was found to be a potent repressor of leukocidins LukED and LukSF-PV. We found that inactivating sarS resulted in increased virulence both in an ex vivo model using primary human neutrophils and in an in vivo infection model in mice. Further experimentation revealed that SarS represses leukocidins by serving as an activator of Rot, a critical repressor of toxins, as well as by directly binding and repressing the leukocidin promoters. By studying contemporary clinical isolates, we identified naturally occurring mutations in the sarS promoter that resulted in overexpression of sarS and increased repression of leukocidins in USA300 bloodstream clinical isolates. Overall, these data establish SarS as an important repressor of leukocidins and expand our understanding of how these virulence factors are being regulated in vitro and in vivo by S. aureus.
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Affiliation(s)
- Exene E. Anderson
- Department of Microbiology, New York University Grossman School of Medicine, New York, New York, USA
| | - Sophie Dyzenhaus
- Department of Microbiology, New York University Grossman School of Medicine, New York, New York, USA
| | - Juliana K. Ilmain
- Department of Microbiology, New York University Grossman School of Medicine, New York, New York, USA
| | - Mitchell J. Sullivan
- Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | - Harm van Bakel
- Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, New York, USA
- Icahn Genomics Institute, Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | - Victor J. Torres
- Department of Microbiology, New York University Grossman School of Medicine, New York, New York, USA
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6
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Staphylococcus aureus induces a muted host response in human blood that blunts the recruitment of neutrophils. Proc Natl Acad Sci U S A 2022; 119:e2123017119. [PMID: 35881802 PMCID: PMC9351360 DOI: 10.1073/pnas.2123017119] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Staphylococcus aureus is an opportunistic pathogen and chief among bloodstream-infecting bacteria. S. aureus produces an array of human-specific virulence factors that may contribute to immune suppression. Here, we defined the response of primary human phagocytes following infection with S. aureus using RNA-sequencing (RNA-Seq). We found that the overall transcriptional response to S. aureus was weak both in the number of genes and in the magnitude of response. Using an ex vivo bacteremia model with fresh human blood, we uncovered that infection with S. aureus resulted in the down-regulation of genes related to innate immune response and cytokine and chemokine signaling. This muted transcriptional response was conserved across diverse S. aureus clones but absent in blood exposed to heat-killed S. aureus or blood infected with the less virulent staphylococcal species Staphylococcus epidermidis. Notably, this signature was also present in patients with S. aureus bacteremia. We identified the master regulator S. aureus exoprotein expression (SaeRS) and the SaeRS-regulated pore-forming toxins as key mediators of the transcriptional suppression. The S. aureus-mediated suppression of chemokine and cytokine transcription was reflected by circulating protein levels in the plasma. Wild-type S. aureus elicited a soluble milieu that was restrictive in the recruitment of human neutrophils compared with strains lacking saeRS. Thus, S. aureus blunts the inflammatory response resulting in impaired neutrophil recruitment, which could promote the survival of the pathogen during invasive infection.
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7
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Targeting the Holy Triangle of Quorum Sensing, Biofilm Formation, and Antibiotic Resistance in Pathogenic Bacteria. Microorganisms 2022; 10:microorganisms10061239. [PMID: 35744757 PMCID: PMC9228545 DOI: 10.3390/microorganisms10061239] [Citation(s) in RCA: 43] [Impact Index Per Article: 21.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2022] [Revised: 06/12/2022] [Accepted: 06/14/2022] [Indexed: 12/12/2022] Open
Abstract
Chronic and recurrent bacterial infections are frequently associated with the formation of biofilms on biotic or abiotic materials that are composed of mono- or multi-species cultures of bacteria/fungi embedded in an extracellular matrix produced by the microorganisms. Biofilm formation is, among others, regulated by quorum sensing (QS) which is an interbacterial communication system usually composed of two-component systems (TCSs) of secreted autoinducer compounds that activate signal transduction pathways through interaction with their respective receptors. Embedded in the biofilms, the bacteria are protected from environmental stress stimuli, and they often show reduced responses to antibiotics, making it difficult to eradicate the bacterial infection. Besides reduced penetration of antibiotics through the intricate structure of the biofilms, the sessile biofilm-embedded bacteria show reduced metabolic activity making them intrinsically less sensitive to antibiotics. Moreover, they frequently express elevated levels of efflux pumps that extrude antibiotics, thereby reducing their intracellular levels. Some efflux pumps are involved in the secretion of QS compounds and biofilm-related materials, besides being important for removing toxic substances from the bacteria. Some efflux pump inhibitors (EPIs) have been shown to both prevent biofilm formation and sensitize the bacteria to antibiotics, suggesting a relationship between these processes. Additionally, QS inhibitors or quenchers may affect antibiotic susceptibility. Thus, targeting elements that regulate QS and biofilm formation might be a promising approach to combat antibiotic-resistant biofilm-related bacterial infections.
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8
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The Major Autolysin Atl Regulates the Virulence of Staphylococcus aureus by Controlling the Sorting of LukAB. Infect Immun 2022; 90:e0005622. [PMID: 35258336 PMCID: PMC9022505 DOI: 10.1128/iai.00056-22] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Infections caused by the Gram-positive bacterium Staphylococcus aureus remain a significant health threat globally. The production of bicomponent pore-forming leukocidins plays an important role in S. aureus pathogenesis. Transcriptionally, these toxins are primarily regulated by the Sae and Agr regulatory systems. However, the posttranslational regulation of these toxins is largely unexplored. In particular, one of the leukocidins, LukAB, has been shown to be both secreted into the extracellular milieu and associated with the bacterial cell envelope. Here, we report that a major cell wall hydrolase, autolysin (Atl), controls the sorting of LukAB from the cell envelope to the extracellular milieu, an effect independent of transcriptional regulation. By influencing the sorting of LukAB, Atl modulates S. aureus cytotoxicity toward primary human neutrophils. Mechanistically, we found that the reduction in peptidoglycan cleavage and increased LukAB secretion in the atl mutant can be reversed through the supplementation of exogenous mutanolysin. Altogether, our study revealed that the cell wall hydrolase activity of Atl and the cleavage of peptidoglycan play an important role in controlling the sorting of S. aureus toxins during secretion.
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9
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Abstract
Staphylococcus aureus is both a commensal and a pathogenic bacterium for humans. Its ability to induce severe infections is based on a wide range of virulence factors. S. aureus community-acquired pneumonia (SA-CAP) is rare and severe, and the contribution of certain virulence factors in this disease has been recognized over the past 2 decades. First, the factors involved in metabolism adaptation are crucial for S. aureus survival in the lower respiratory tract, and toxins and enzymes are required for it to cross the pulmonary epithelial barrier. S. aureus subsequently faces host defense mechanisms, including the epithelial barrier, but most importantly the immune system. Here, again, S. aureus uses myriad virulence factors to successfully escape from the host's defenses and takes advantage of them. The impact of S. aureus virulence, combined with the collateral damage caused by an overwhelming immune response, leads to severe tissue damage and adverse clinical outcomes. In this review, we summarize step by step all of the S. aureus factors implicated in CAP and described to date, and we provide an outlook for future research.
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Affiliation(s)
- Mariane Pivard
- CIRI, Centre International de Recherche en Infectiologie, Université de Lyon, Inserm, U1111, Université Claude Bernard Lyon 1, CNRS, UMR5308, ENS de Lyon, Lyon, France
| | - Karen Moreau
- CIRI, Centre International de Recherche en Infectiologie, Université de Lyon, Inserm, U1111, Université Claude Bernard Lyon 1, CNRS, UMR5308, ENS de Lyon, Lyon, France
| | - François Vandenesch
- CIRI, Centre International de Recherche en Infectiologie, Université de Lyon, Inserm, U1111, Université Claude Bernard Lyon 1, CNRS, UMR5308, ENS de Lyon, Lyon, France
- Centre National de Référence des Staphylocoques, Institut des agents infectieux, Hospices Civils de Lyon, Lyon, France
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10
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Tuffs SW, Herfst CA, Baroja ML, Podskalniy VA, DeJong EN, Coleman CEM, McCormick JK. Regulation of toxic shock syndrome toxin‐1 by the accessory gene regulator inStaphylococcus aureusis mediated by the repressor of toxins. Mol Microbiol 2019; 112:1163-1177. [DOI: 10.1111/mmi.14353] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/15/2019] [Indexed: 12/13/2022]
Affiliation(s)
- Stephen W. Tuffs
- Department of Microbiology and Immunology University of Western Ontario London Ontario Canada
| | - Christine A. Herfst
- Department of Microbiology and Immunology University of Western Ontario London Ontario Canada
- Lawson Health Research Institute London Ontario Canada
| | - Miren L. Baroja
- Department of Microbiology and Immunology University of Western Ontario London Ontario Canada
- Lawson Health Research Institute London Ontario Canada
| | - Vladyslav A. Podskalniy
- Department of Microbiology and Immunology University of Western Ontario London Ontario Canada
| | - Erica N. DeJong
- Department of Microbiology and Immunology University of Western Ontario London Ontario Canada
| | - Charlotte E. M. Coleman
- Department of Microbiology and Immunology University of Western Ontario London Ontario Canada
| | - John K. McCormick
- Department of Microbiology and Immunology University of Western Ontario London Ontario Canada
- Lawson Health Research Institute London Ontario Canada
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11
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Regulation of the Staphylococcal Superantigen-Like Protein 1 Gene of Community-Associated Methicillin-Resistant Staphylococcus aureus in Murine Abscesses. Toxins (Basel) 2019; 11:toxins11070391. [PMID: 31277443 PMCID: PMC6669464 DOI: 10.3390/toxins11070391] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2019] [Revised: 06/28/2019] [Accepted: 07/02/2019] [Indexed: 12/25/2022] Open
Abstract
Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) causes substantial skin and soft tissue infections annually in the United States and expresses numerous virulence factors, including a family of toxins known as the staphylococcal superantigen-like (SSL) proteins. Many of the SSL protein structures have been determined and implicated in immune system avoidance, but the full scope that these proteins play in different infection contexts remains unknown and continues to warrant investigation. Analysis of ssl gene regulation may provide valuable information related to the function of these proteins. To determine the transcriptional regulation of the ssl1 gene of CA-MRSA strain MW2, an ssl1 promoter::lux fusion was constructed and transformed into S.aureus strains RN6390 and Newman. Resulting strains were grown in a defined minimal medium (DSM) broth and nutrient-rich brain-heart infusion (BHI) broth and expression was determined by luminescence. Transcription of ssl1 was up-regulated and occurred earlier during growth in DSM broth compared to BHI broth suggesting expression is regulated by nutrient availability. RN6390 and Newman strains containing the ssl1::lux fusion were also used to analyze regulation in vivo using a mouse abscess model of infection. A marked increase in ssl1 transcription occurred early during infection, suggesting SSL1 is important during early stages of infection, perhaps to avoid the immune system.
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Abstract
Staphylococcus aureus is a Gram-positive opportunistic pathogen that has evolved a complex regulatory network to control virulence. One of the main functions of this interconnected network is to sense various environmental cues and respond by altering the production of virulence factors necessary for survival in the host, including cell surface adhesins and extracellular enzymes and toxins. Of these S. aureus regulatory systems, one of the best studied is the accessory gene regulator (agr), which is a quorum-sensing system that senses the local concentration of a cyclic peptide signaling molecule. This system allows S. aureus to sense its own population density and translate this information into a specific gene expression pattern. Besides agr, this pathogen uses other two-component systems to sense specific cues and coordinates responses with cytoplasmic regulators of the SarA protein family and alternative sigma factors. These divergent regulatory systems integrate the various environmental and host-derived signals into a network that ensures optimal pathogen response to the changing conditions. This article gives an overview of the most important and best-studied S. aureus regulatory systems and summarizes the functions of these regulators during host interactions. The regulatory systems discussed include the agr quorum-sensing system; the SaeRS, SrrAB, and ArlRS two-component systems, the cytoplasmic SarA-family regulators (SarA, Rot, and MgrA); and the alternative sigma factors (SigB and SigH).
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Cosgriff CJ, White CR, Teoh WP, Grayczyk JP, Alonzo F. Control of Staphylococcus aureus Quorum Sensing by a Membrane-Embedded Peptidase. Infect Immun 2019; 87:e00019-19. [PMID: 30833334 PMCID: PMC6479040 DOI: 10.1128/iai.00019-19] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2019] [Accepted: 02/23/2019] [Indexed: 02/08/2023] Open
Abstract
Gram-positive bacteria process and release small peptides, or pheromones, that act as signals for the induction of adaptive traits, including those involved in pathogenesis. One class of small signaling pheromones is the cyclic autoinducing peptides (AIPs), which regulate expression of genes that orchestrate virulence and persistence in a range of microbes, including staphylococci, listeriae, clostridia, and enterococci. In a genetic screen for Staphylococcus aureus secreted virulence factors, we identified an S. aureus mutant containing an insertion in the gene SAUSA300_1984 (mroQ), which encodes a putative membrane-embedded metalloprotease. A ΔmroQ mutant exhibited impaired induction of Toll-like receptor 2-dependent inflammatory responses from macrophages but elicited greater production of the inflammatory cytokine interleukin-1β and was attenuated in a murine skin and soft tissue infection model. The ΔmroQ mutant phenocopies an S. aureus mutant containing a deletion of the accessory gene regulatory system (Agr), wherein both strains have significantly reduced production of secreted toxins and virulence factors but increased surface protein A abundance. The Agr system controls virulence factor gene expression in S. aureus by sensing the accumulation of AIP via the histidine kinase AgrC and the response regulator AgrA. We provide evidence to suggest that MroQ acts within the Agr pathway to facilitate the optimal processing or export of AIP for signal amplification through AgrC/A and induction of virulence factor gene expression. Mutation of MroQ active-site residues significantly reduces AIP signaling and attenuates virulence. Altogether, this work identifies a new component of the Agr quorum-sensing circuit that is critical for the production of S. aureus virulence factors.
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Affiliation(s)
- Chance J Cosgriff
- Department of Microbiology and Immunology, Loyola University Chicago Stritch School of Medicine, Maywood, Illinois, USA
| | - Chelsea R White
- Department of Microbiology and Immunology, Loyola University Chicago Stritch School of Medicine, Maywood, Illinois, USA
| | - Wei Ping Teoh
- Department of Microbiology and Immunology, Loyola University Chicago Stritch School of Medicine, Maywood, Illinois, USA
| | - James P Grayczyk
- Department of Microbiology and Immunology, Loyola University Chicago Stritch School of Medicine, Maywood, Illinois, USA
| | - Francis Alonzo
- Department of Microbiology and Immunology, Loyola University Chicago Stritch School of Medicine, Maywood, Illinois, USA
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Abstract
Antigen-presenting cells such as dendritic cells (DCs) fulfill an indispensable role in the development of adaptive immunity by producing proinflammatory cytokines and presenting microbial antigens to lymphocytes to trigger a faster, specific, and long-lasting immune response. Here, we studied the effect of Staphylococcus aureus toxins on human DCs. We discovered that the leukocidin LukAB hinders the development of adaptive immunity by targeting human DCs. The ability of S. aureus to blunt the function of DCs could help explain the high frequency of recurrent S. aureus infections. Taken together, the results from this study suggest that therapeutically targeting the S. aureus leukocidins may boost effective innate and adaptive immune responses by protecting innate leukocytes, enabling proper antigen presentation and T cell activation. Staphylococcus aureus is a human pathogen responsible for high morbidity and mortality worldwide. Recurrent infections with this bacterium are common, suggesting that S. aureus thwarts the development of sterilizing immunity. S. aureus strains that cause disease in humans produce up to five different bicomponent toxins (leukocidins) that target and lyse neutrophils, innate immune cells that represent the first line of defense against S. aureus infections. However, little is known about the role of leukocidins in blunting adaptive immunity. Here, we explored the effects of leukocidins on human dendritic cells (DCs), antigen-presenting cells required for the development of adaptive immunity. Using an ex vivo infection model of primary human monocyte-derived dendritic cells, we found that S. aureus, including strains from different clonal complexes and drug resistance profiles, effectively kills DCs despite efficient phagocytosis. Although all purified leukocidins could kill DCs, infections with live bacteria revealed that S. aureus targets and kills DCs primarily via the activity of leukocidin LukAB. Moreover, using coculture experiments performed with DCs and autologous CD4+ T lymphocytes, we found that LukAB inhibits DC-mediated activation and proliferation of primary human T cells. Taken together, the data determined in the study reveal a novel immunosuppressive strategy of S. aureus whereby the bacterium blunts the development of adaptive immunity via LukAB-mediated injury of DCs.
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Tang A, Caballero AR, Bierdeman MA, Marquart ME, Foster TJ, Monk IR, O'Callaghan RJ. Staphylococcus aureus Superantigen-Like Protein SSL1: A Toxic Protease. Pathogens 2019; 8:pathogens8010002. [PMID: 30609641 PMCID: PMC6471365 DOI: 10.3390/pathogens8010002] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2018] [Revised: 12/12/2018] [Accepted: 12/20/2018] [Indexed: 12/24/2022] Open
Abstract
Staphylococcus aureus is a major cause of corneal infections that can cause reduced vision, even blindness. Secreted toxins cause tissue damage and inflammation resulting in scars that lead to vision loss. Identifying tissue damaging proteins is a prerequisite to limiting these harmful reactions. The present study characterized a previously unrecognized S. aureus toxin. This secreted toxin was purified from strain Newman ΔhlaΔhlg, the N-terminal sequence determined, the gene cloned, and the purified recombinant protein was tested in the rabbit cornea. The virulence of a toxin deletion mutant was compared to its parent and the mutant after gene restoration (rescue strain). The toxin (23 kDa) had an N-terminal sequence matching the Newman superantigen-like protein SSL1. An SSL1 homodimer (46 kDa) had proteolytic activity as demonstrated by zymography and cleavage of a synthetic substrate, collagens, and cytokines (IL-17A, IFN-γ, and IL-8); the protease was susceptible to serine protease inhibitors. As compared to the parent and rescue strains, the ssl1 mutant had significantly reduced virulence, but not reduced bacterial growth, in vivo. The ocular isolates tested had the ssl1 gene, with allele type 2 being the predominant type. SSL1 is a protease with corneal virulence and activity on host defense and structural proteins.
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Affiliation(s)
- Aihua Tang
- Department of Microbiology and Immunology, University of Mississippi Medical Center, Jackson, MS 39216, USA.
| | - Armando R Caballero
- Department of Microbiology and Immunology, University of Mississippi Medical Center, Jackson, MS 39216, USA.
| | - Michael A Bierdeman
- Department of Microbiology and Immunology, University of Mississippi Medical Center, Jackson, MS 39216, USA.
| | - Mary E Marquart
- Department of Microbiology and Immunology, University of Mississippi Medical Center, Jackson, MS 39216, USA.
| | - Timothy J Foster
- Department of Microbiology, Moyne Institute of Preventive Medicine, Trinity College, Dublin 2, D02 PN40, Ireland.
| | - Ian R Monk
- Department of Microbiology, Moyne Institute of Preventive Medicine, Trinity College, Dublin 2, D02 PN40, Ireland.
- Department of Microbiology and Immunology, Doherty Institute for Infection and Immunity, University of Melbourne, 3000 Melbourne, Australia.
| | - Richard J O'Callaghan
- Department of Microbiology and Immunology, University of Mississippi Medical Center, Jackson, MS 39216, USA.
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16
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Gajenthra Kumar N, Contaifer D, Baker PRS, Ekroos K, Jefferson KK, Wijesinghe DS. Untargeted lipidomic analysis to broadly characterize the effects of pathogenic and non-pathogenic staphylococci on mammalian lipids. PLoS One 2018; 13:e0206606. [PMID: 30379915 PMCID: PMC6209338 DOI: 10.1371/journal.pone.0206606] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2018] [Accepted: 10/16/2018] [Indexed: 11/19/2022] Open
Abstract
Modification of the host lipidome via secreted enzymes is an integral, but often overlooked aspect of bacterial pathogenesis. In the current era of prevalent antibiotic resistance, knowledge regarding critical host pathogen lipid interactions has the potential for use in developing novel antibacterial agents. While most studies to date on this matter have focused on specific lipids, or select lipid classes, this provides an incomplete picture. Modern methods of untargeted lipidomics have the capacity to overcome these gaps in knowledge and provide a comprehensive understanding of the role of lipid metabolism in the pathogenesis of infections. In an attempt to determine the role of lipid modifying enzymes produced by staphylococci, we exposed bovine heart lipids, a standardized model for the mammalian lipidome, to spent medium from staphylococcal cultures, and analyzed lipid molecular changes by MS/MSALL shotgun lipidomics. We elucidate distinct effects of different staphylococcal isolates, including 4 clinical isolates of the pathogenic species Staphylococcus aureus, a clinical isolate of the normally commensal species S. epidermidis, and the non-pathogenic species S. carnosus. Two highly virulent strains of S. aureus had a more profound effect on mammalian lipids and modified more lipid classes than the other staphylococcal strains. Our studies demonstrate the utility of the applied untargeted lipidomics methodology to profile lipid changes induced by different bacterial secretomes. Finally, we demonstrate the promise of this lipidomics approach in assessing the specificity of bacterial enzymes for mammalian lipid classes. Our data suggests that there may be a correlation between the bacterial expression of lipid-modifying enzymes and virulence, and could facilitate the guided discovery of lipid pathways required for bacterial infections caused by S. aureus and thereby provide insights into the generation of novel antibacterial agents.
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Affiliation(s)
- Naren Gajenthra Kumar
- Department of Microbiology and Immunology, School of Medicine, Virginia Commonwealth University, Richmond, Virginia, United States of America
| | - Daniel Contaifer
- Department of Pharmacotherapy and Outcomes Sciences, School of Pharmacy, Virginia Commonwealth University, Richmond, Virginia, United States of America
| | | | - Kim Ekroos
- Lipidomics Consulting Ltd., Esbo, Finland
| | - Kimberly K. Jefferson
- Department of Microbiology and Immunology, School of Medicine, Virginia Commonwealth University, Richmond, Virginia, United States of America
| | - Dayanjan S. Wijesinghe
- Department of Pharmacotherapy and Outcomes Sciences, School of Pharmacy, Virginia Commonwealth University, Richmond, Virginia, United States of America
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Nutritional Regulation of the Sae Two-Component System by CodY in Staphylococcus aureus. J Bacteriol 2018; 200:JB.00012-18. [PMID: 29378891 DOI: 10.1128/jb.00012-18] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2018] [Accepted: 01/23/2018] [Indexed: 01/22/2023] Open
Abstract
Staphylococcus aureus subverts innate defenses during infection in part by killing host immune cells to exacerbate disease. This human pathogen intercepts host cues and activates a transcriptional response via the S. aureus exoprotein expression (SaeR/SaeS [SaeR/S]) two-component system to secrete virulence factors critical for pathogenesis. We recently showed that the transcriptional repressor CodY adjusts nuclease (nuc) gene expression via SaeR/S, but the mechanism remained unknown. Here, we identified two CodY binding motifs upstream of the sae P1 promoter, which suggested direct regulation by this global regulator. We show that CodY shares a binding site with the positive activator SaeR and that alleviating direct CodY repression at this site is sufficient to abrogate stochastic expression, suggesting that CodY represses sae expression by blocking SaeR binding. Epistasis experiments support a model that CodY also controls sae indirectly through Agr and Rot-mediated repression of the sae P1 promoter. We also demonstrate that CodY repression of sae restrains production of secreted cytotoxins that kill human neutrophils. We conclude that CodY plays a previously unrecognized role in controlling virulence gene expression via SaeR/S and suggest a mechanism by which CodY acts as a master regulator of pathogenesis by tying nutrient availability to virulence gene expression.IMPORTANCE Bacterial mechanisms that mediate the switch from a commensal to pathogenic lifestyle are among the biggest unanswered questions in infectious disease research. Since the expression of most virulence genes is often correlated with nutrient depletion, this implies that virulence is a response to the lack of nourishment in host tissues and that pathogens like S. aureus produce virulence factors in order to gain access to nutrients in the host. Here, we show that specific nutrient depletion signals appear to be funneled to the SaeR/S system through the global regulator CodY. Our findings reveal a strategy by which S. aureus delays the production of immune evasion and immune-cell-killing proteins until key nutrients are depleted.
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O'Callaghan RJ. The Pathogenesis of Staphylococcus aureus Eye Infections. Pathogens 2018; 7:pathogens7010009. [PMID: 29320451 PMCID: PMC5874735 DOI: 10.3390/pathogens7010009] [Citation(s) in RCA: 58] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2017] [Revised: 01/02/2018] [Accepted: 01/04/2018] [Indexed: 02/07/2023] Open
Abstract
Staphylococcus aureus is a major pathogen of the eye able to infect the tear duct, eyelid, conjunctiva, cornea, anterior and posterior chambers, and the vitreous chamber. Of these infections, those involving the cornea (keratitis) or the inner chambers of the eye (endophthalmitis) are the most threatening because of their potential to cause a loss in visual acuity or even blindness. Each of these ocular sites is protected by the constitutive expression of a variety of antimicrobial factors and these defenses are augmented by a protective host response to the organism. Such infections often involve a predisposing factor that weakens the defenses, such as the use of contact lenses prior to the development of bacterial keratitis or, for endophthalmitis, the trauma caused by cataract surgery or intravitreal injection. The structural carbohydrates of the bacterial surface induce an inflammatory response able to reduce the bacterial load, but contribute to the tissue damage. A variety of bacterial secreted proteins including alpha-toxin, beta-toxin, gamma-toxin, Panton-Valentine leukocidin and other two-component leukocidins mediate tissue damage and contribute to the induction of the inflammatory response. Quantitative animal models of keratitis and endophthalmitis have provided insights into the S. aureus virulence and host factors active in limiting such infections.
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Affiliation(s)
- Richard J O'Callaghan
- Department of Microbiology and Immunology, University of Mississippi Medical Center, 2500 N. State St., Jackson, MS 39216, USA.
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Balasubramanian D, Harper L, Shopsin B, Torres VJ. Staphylococcus aureus pathogenesis in diverse host environments. Pathog Dis 2017; 75:ftx005. [PMID: 28104617 DOI: 10.1093/femspd/ftx005] [Citation(s) in RCA: 140] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2016] [Accepted: 01/18/2017] [Indexed: 12/21/2022] Open
Abstract
Staphylococcus aureus is an eminent human pathogen that can colonize the human host and cause severe life-threatening illnesses. This bacterium can reside in and infect a wide range of host tissues, ranging from superficial surfaces like the skin to deeper tissues such as in the gastrointestinal tract, heart and bones. Due to its multifaceted lifestyle, S. aureus uses complex regulatory networks to sense diverse signals that enable it to adapt to different environments and modulate virulence. In this minireview, we explore well-characterized environmental and host cues that S. aureus responds to and describe how this pathogen modulates virulence in response to these signals. Lastly, we highlight therapeutic approaches undertaken by several groups to inhibit both signaling and the cognate regulators that sense and transmit these signals downstream.
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Affiliation(s)
- Divya Balasubramanian
- Department of Microbiology, New York University School of Medicine, New York, NY 10016, USA
| | - Lamia Harper
- Department of Microbiology, New York University School of Medicine, New York, NY 10016, USA
| | - Bo Shopsin
- Department of Medicine, Division of Infectious Diseases, New York University School of Medicine, New York, NY 10016 USA
| | - Victor J Torres
- Department of Microbiology, New York University School of Medicine, New York, NY 10016, USA
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20
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Staphylococcus aureus Strain Newman D2C Contains Mutations in Major Regulatory Pathways That Cripple Its Pathogenesis. J Bacteriol 2017; 199:JB.00476-17. [PMID: 28924032 DOI: 10.1128/jb.00476-17] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2017] [Accepted: 09/15/2017] [Indexed: 12/27/2022] Open
Abstract
Staphylococcus aureus is a major human pathogen that imposes a great burden on the health care system. In the development of antistaphylococcal modalities intended to reduce the burden of staphylococcal disease, it is imperative to select appropriate models of S. aureus strains when assessing the efficacy of novel agents. Here, using whole-genome sequencing, we reveal that the commonly used strain Newman D2C from the American Type Culture Collection (ATCC) contains mutations that render the strain essentially avirulent. Importantly, Newman D2C is often inaccurately referred to as simply "Newman" in many publications, leading investigators to believe it is the well-described pathogenic strain Newman. This study reveals that Newman D2C carries a stop mutation in the open reading frame of the virulence gene regulator, agrA In addition, Newman D2C carries a single-nucleotide polymorphism (SNP) in the global virulence regulator gene saeR that results in loss of protein function. This loss of function is highlighted by complementation studies, where the saeR allele from Newman D2C is incapable of restoring functionality to an saeR-null mutant. Additional functional assessment was achieved through the use of biochemical assays for protein secretion, ex vivo intoxications of human immune cells, and in vivo infections. Altogether, our study highlights the importance of judiciously screening for genetic changes in model S. aureus strains when assessing pathogenesis or the efficacy of novel agents. Moreover, we have identified a novel SNP in the virulence regulator gene saeR that directly affects the ability of the protein product to activate S. aureus virulence pathways.IMPORTANCE Staphylococcus aureus is a human pathogen that imposes an enormous burden on health care systems worldwide. This bacterium is capable of evoking a multitude of disease states that can range from self-limiting skin infections to life-threatening bacteremia. To combat these infections, numerous investigations are under way to develop therapeutics capable of thwarting the deadly effects of the bacterium. To generate successful treatments, it is of paramount importance that investigators use suitable models for examining the efficacy of the drugs under study. Here, we demonstrate that a strain of S. aureus commonly used for drug efficacy studies is severely mutated and displays markedly reduced pathogenicity. As such, the organism is an inappropriate model for disease studies.
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Peng H, Zhang Y, Palmer LD, Kehl-Fie TE, Skaar EP, Trinidad JC, Giedroc DP. Hydrogen Sulfide and Reactive Sulfur Species Impact Proteome S-Sulfhydration and Global Virulence Regulation in Staphylococcus aureus. ACS Infect Dis 2017; 3:744-755. [PMID: 28850209 DOI: 10.1021/acsinfecdis.7b00090] [Citation(s) in RCA: 60] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Hydrogen sulfide (H2S) is thought to protect bacteria from oxidative stress, but a comprehensive understanding of its function in bacteria is largely unexplored. In this study, we show that the human pathogen Staphylococcus aureus (S. aureus) harbors significant effector molecules of H2S signaling, reactive sulfur species (RSS), as low molecular weight persulfides of bacillithiol, coenzyme A, and cysteine, and significant inorganic polysulfide species. We find that proteome S-sulfhydration, a post-translational modification (PTM) in H2S signaling, is widespread in S. aureus. RSS levels modulate the expression of secreted virulence factors and the cytotoxicity of the secretome, consistent with an S-sulfhydration-dependent inhibition of DNA binding by MgrA, a global virulence regulator. Two previously uncharacterized thioredoxin-like proteins, denoted TrxP and TrxQ, are S-sulfhydrated in sulfide-stressed cells and are capable of reducing protein hydrodisulfides, suggesting that this PTM is potentially regulatory in S. aureus. In conclusion, our results reveal that S. aureus harbors a pool of proteome- and metabolite-derived RSS capable of impacting protein activities and gene regulation and that H2S signaling can be sensed by global regulators to affect the expression of virulence factors.
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Affiliation(s)
- Hui Peng
- Department of Chemistry, Indiana University, 800 E. Kirkwood Drive, Bloomington, Indiana 47405-7102, United States
- Graduate Program in Biochemistry, Indiana University, 212 S. Hawthorne Drive, Bloomington, Indiana 47405, United States
| | - Yixiang Zhang
- Department of Chemistry, Indiana University, 800 E. Kirkwood Drive, Bloomington, Indiana 47405-7102, United States
- Laboratory for Biological Mass Spectrometry,
Department of Chemistry, Indiana University, Simon Hall 120B, 212 S. Hawthorne
Drive, Bloomington, Indiana 47405, United States
| | - Lauren D. Palmer
- Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center, 1161 21st Avenue South, Nashville, Tennessee 37232-2363, United States
| | - Thomas E. Kehl-Fie
- Department of Microbiology, University of Illinois Urbana−Champaign, 601 South Goodwin Avenue, Urbana, Illinois 61801, United States
| | - Eric P. Skaar
- Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center, 1161 21st Avenue South, Nashville, Tennessee 37232-2363, United States
| | - Jonathan C. Trinidad
- Department of Chemistry, Indiana University, 800 E. Kirkwood Drive, Bloomington, Indiana 47405-7102, United States
- Laboratory for Biological Mass Spectrometry,
Department of Chemistry, Indiana University, Simon Hall 120B, 212 S. Hawthorne
Drive, Bloomington, Indiana 47405, United States
| | - David P. Giedroc
- Department of Chemistry, Indiana University, 800 E. Kirkwood Drive, Bloomington, Indiana 47405-7102, United States
- Department
of Molecular and Cellular Biochemistry, Indiana University, 212 S. Hawthorne Drive, Bloomington, Indiana 47405, United States
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Rom JS, Atwood DN, Beenken KE, Meeker DG, Loughran AJ, Spencer HJ, Lantz TL, Smeltzer MS. Impact of Staphylococcus aureus regulatory mutations that modulate biofilm formation in the USA300 strain LAC on virulence in a murine bacteremia model. Virulence 2017; 8:1776-1790. [PMID: 28910576 PMCID: PMC5810510 DOI: 10.1080/21505594.2017.1373926] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Staphylococcus aureus causes acute and chronic forms of infection, the latter often associated with formation of a biofilm. It has previously been demonstrated that mutation of atl, codY, rot, sarA, and sigB limits biofilm formation in the USA300 strain LAC while mutation of agr, fur, and mgrA has the opposite effect. Here we used a murine sepsis model to assess the impact of these same loci in acute infection. Mutation of agr, atl, and fur had no impact on virulence, while mutation of mgrA and rot increased virulence. In contrast, mutation of codY, sarA, and sigB significantly attenuated virulence. Mutation of sigB resulted in reduced accumulation of AgrA and SarA, while mutation of sarA resulted in reduced accumulation of AgrA, but this cannot account for the reduced virulence of sarA or sigB mutants because the isogenic agr mutant was not attenuated. Indeed, as assessed by accumulation of alpha toxin and protein A, all of the mutants we examined exhibited unique phenotypes by comparison to an agr mutant and to each other. Attenuation of the sarA, sigB and codY mutants was correlated with increased production of extracellular proteases and global changes in extracellular protein profiles. These results suggest that the inability to repress the production of extracellular proteases plays a key role in attenuating the virulence of S. aureus in acute as well as chronic, biofilm-associated infections, thus opening up the possibility that strategies aimed at the de-repression of protease production could be used to broad therapeutic advantage. They also suggest that the impact of codY, sarA, and sigB on protease production occurs via an agr-independent mechanism.
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Affiliation(s)
- Joseph S Rom
- a Department of Microbiology and Immunology , University of Arkansas for Medical Sciences , Little Rock , AR , USA
| | - Danielle N Atwood
- a Department of Microbiology and Immunology , University of Arkansas for Medical Sciences , Little Rock , AR , USA
| | - Karen E Beenken
- a Department of Microbiology and Immunology , University of Arkansas for Medical Sciences , Little Rock , AR , USA
| | - Daniel G Meeker
- a Department of Microbiology and Immunology , University of Arkansas for Medical Sciences , Little Rock , AR , USA
| | - Allister J Loughran
- a Department of Microbiology and Immunology , University of Arkansas for Medical Sciences , Little Rock , AR , USA
| | - Horace J Spencer
- b Department of Biostatistics , University of Arkansas for Medical Sciences , Little Rock , AR , USA
| | - Tamara L Lantz
- a Department of Microbiology and Immunology , University of Arkansas for Medical Sciences , Little Rock , AR , USA
| | - Mark S Smeltzer
- a Department of Microbiology and Immunology , University of Arkansas for Medical Sciences , Little Rock , AR , USA.,c Department of Orthopaedic Surgery , University of Arkansas for Medical Sciences , Little Rock , AR , USA.,d Department of Pathology , University of Arkansas for Medical Sciences , Little Rock , AR , USA
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Dietary Manganese Promotes Staphylococcal Infection of the Heart. Cell Host Microbe 2017; 22:531-542.e8. [PMID: 28943329 DOI: 10.1016/j.chom.2017.08.009] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2017] [Revised: 06/29/2017] [Accepted: 08/17/2017] [Indexed: 01/25/2023]
Abstract
Diet, and specifically dietary metals, can modify the risk of infection. However, the mechanisms by which manganese (Mn), a common dietary supplement, alters infection remain unexplored. We report that dietary Mn levels dictate the outcome of systemic infections caused by Staphylococcus aureus, a leading cause of bacterial endocarditis. Mice fed a high Mn diet display alterations in Mn levels and localization within infected tissues, and S. aureus virulence and infection of the heart are enhanced. Although the canonical mammalian Mn-sequestering protein calprotectin surrounds staphylococcal heart abscesses, calprotectin is not released into the abscess nidus and does not limit Mn in this organ. Consequently, excess Mn is bioavailable to S. aureus in the heart. Bioavailable Mn is utilized by S. aureus to detoxify reactive oxygen species and protect against neutrophil killing, enhancing fitness within the heart. Therefore, a single dietary modification overwhelms vital host antimicrobial strategies, leading to fatal staphylococcal infection.
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Langley RJ, Ting YT, Clow F, Young PG, Radcliff FJ, Choi JM, Sequeira RP, Holtfreter S, Baker H, Fraser JD. Staphylococcal enterotoxin-like X (SElX) is a unique superantigen with functional features of two major families of staphylococcal virulence factors. PLoS Pathog 2017; 13:e1006549. [PMID: 28880913 PMCID: PMC5589262 DOI: 10.1371/journal.ppat.1006549] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2017] [Accepted: 07/24/2017] [Indexed: 11/23/2022] Open
Abstract
Staphylococcus aureus is an opportunistic pathogen that produces many virulence factors. Two major families of which are the staphylococcal superantigens (SAgs) and the Staphylococcal Superantigen-Like (SSL) exoproteins. The former are immunomodulatory toxins that induce a Vβ-specific activation of T cells, while the latter are immune evasion molecules that interfere with a wide range of innate immune defences. The superantigenic properties of Staphylococcal enterotoxin-like X (SElX) have recently been established. We now reveal that SElX also possesses functional characteristics of the SSLs. A region of SElX displays high homology to the sialyl-lactosamine (sLacNac)-specific binding site present in a sub-family of SSLs. By analysing the interaction of SElX with sLacNac-containing glycans we show that SElX has an equivalent specificity and host cell binding range to the SSLs. Mutation of key amino acids in this conserved region affects the ability of SElX to bind to cells of myeloid origin and significantly reduces its ability to protect S. aureus from destruction in a whole blood killing (WBK) assay. Like the SSLs, SElX is up-regulated early during infection and is under the control of the S. aureus exotoxin expression (Sae) two component gene regulatory system. Additionally, the structure of SElX in complex with the sLacNac-containing tetrasaccharide sialyl Lewis X (sLeX) reveals that SElX is a unique single-domain SAg. In summary, SElX is an ‘SSL-like’ SAg. The ability of Staphylococcus aureus to cause disease can be attributed to the wide range of toxins and immune evasion molecules it produces. The 25-member superantigen (SAg) family of toxins disrupts adaptive immunity by activating large proportions of T cells. In contrast, the structurally-related 14-member Staphylococcal Superantigen-Like (SSL) family inhibits a wide range of innate immune functions. We have discovered that the SAg staphylococcal enterotoxin-like X (SElX) has the sialylated-glycan-dependent active site found in a sub-family of SSLs. Through this site it possesses the ability to affect host innate immunity defences. By solving the X-ray crystal structure of SElX we have also discovered that SElX is a unique single-domain SAg. While it retains a typical β-grasp domain, it lacks the OB-fold domain that is present in all other staphylococcal SAgs.
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Affiliation(s)
- Ries J. Langley
- School of Medical Sciences, and The Maurice Wilkins Centre for Molecular Biodiscovery, the University of Auckland, Auckland, New Zealand
- * E-mail:
| | - Yi Tian Ting
- School of Biological Sciences, and The Maurice Wilkins Centre for Molecular Biodiscovery, the University of Auckland, Auckland, New Zealand
| | - Fiona Clow
- School of Medical Sciences, and The Maurice Wilkins Centre for Molecular Biodiscovery, the University of Auckland, Auckland, New Zealand
| | - Paul G. Young
- School of Biological Sciences, and The Maurice Wilkins Centre for Molecular Biodiscovery, the University of Auckland, Auckland, New Zealand
| | - Fiona J. Radcliff
- School of Medical Sciences, and The Maurice Wilkins Centre for Molecular Biodiscovery, the University of Auckland, Auckland, New Zealand
| | - Jeong Min Choi
- School of Medical Sciences, and The Maurice Wilkins Centre for Molecular Biodiscovery, the University of Auckland, Auckland, New Zealand
| | - Richard P. Sequeira
- School of Medical Sciences, and The Maurice Wilkins Centre for Molecular Biodiscovery, the University of Auckland, Auckland, New Zealand
| | - Silva Holtfreter
- School of Medical Sciences, and The Maurice Wilkins Centre for Molecular Biodiscovery, the University of Auckland, Auckland, New Zealand
| | - Heather Baker
- School of Biological Sciences, and The Maurice Wilkins Centre for Molecular Biodiscovery, the University of Auckland, Auckland, New Zealand
| | - John D. Fraser
- School of Medical Sciences, and The Maurice Wilkins Centre for Molecular Biodiscovery, the University of Auckland, Auckland, New Zealand
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Tuffs SW, James DBA, Bestebroer J, Richards AC, Goncheva MI, O’Shea M, Wee BA, Seo KS, Schlievert PM, Lengeling A, van Strijp JA, Torres VJ, Fitzgerald JR. The Staphylococcus aureus superantigen SElX is a bifunctional toxin that inhibits neutrophil function. PLoS Pathog 2017; 13:e1006461. [PMID: 28880920 PMCID: PMC5589267 DOI: 10.1371/journal.ppat.1006461] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2017] [Accepted: 06/09/2017] [Indexed: 12/29/2022] Open
Abstract
Bacterial superantigens (SAgs) cause Vβ-dependent T-cell proliferation leading to immune dysregulation associated with the pathogenesis of life-threatening infections such as toxic shock syndrome, and necrotizing pneumonia. Previously, we demonstrated that staphylococcal enterotoxin-like toxin X (SElX) from Staphylococcus aureus is a classical superantigen that exhibits T-cell activation in a Vβ-specific manner, and contributes to the pathogenesis of necrotizing pneumonia. Here, we discovered that SElX can also bind to neutrophils from human and other mammalian species and disrupt IgG-mediated phagocytosis. Site-directed mutagenesis of the conserved sialic acid-binding motif of SElX abolished neutrophil binding and phagocytic killing, and revealed multiple glycosylated neutrophil receptors for SElX binding. Furthermore, the neutrophil binding-deficient mutant of SElX retained its capacity for T-cell activation demonstrating that SElX exhibits mechanistically independent activities on distinct cell populations associated with acquired and innate immunity, respectively. Finally, we demonstrated that the neutrophil-binding activity rather than superantigenicity is responsible for the SElX-dependent virulence observed in a necrotizing pneumonia rabbit model of infection. Taken together, we report the first example of a SAg, that can manipulate both the innate and adaptive arms of the human immune system during S. aureus pathogenesis. Staphylococcus aureus is a bacterial pathogen responsible for an array of disease types in healthcare and community settings. One of the keys to the success of this pathogen is its ability to subvert the immune system of the host. Here we demonstrate that the superantigen (SAg) staphylococcal enterotoxin-like toxin X (SElX) contributes to immune evasion by inducing unregulated T-cell proliferation, and by inhibition of phagocytosis by neutrophils. We observed that the capacity to bind neutrophils appears to be central to the SElX-dependent toxicity observed in a necrotising pneumonia infection model in rabbits. We report the first example of a staphylococcal SAg with two independent immunomodulatory functions acting on distinct immune cell types.
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Affiliation(s)
- Stephen W. Tuffs
- The Roslin Institute, University of Edinburgh, Easter Bush Campus, Midlothian, Scotland, United States of America
| | - David B. A. James
- Department of Microbiology, New York University School of Medicine, New York, NY, United Kingdom
| | - Jovanka Bestebroer
- Department Medical Microbiology, UMC Utrecht, Heidelberglaan 100, 3584 CX Utrecht, The Netherlands
| | - Amy C. Richards
- The Roslin Institute, University of Edinburgh, Easter Bush Campus, Midlothian, Scotland, United States of America
| | - Mariya I. Goncheva
- The Roslin Institute, University of Edinburgh, Easter Bush Campus, Midlothian, Scotland, United States of America
| | - Marie O’Shea
- The Roslin Institute, University of Edinburgh, Easter Bush Campus, Midlothian, Scotland, United States of America
| | - Bryan A. Wee
- The Roslin Institute, University of Edinburgh, Easter Bush Campus, Midlothian, Scotland, United States of America
| | - Keun Seok Seo
- Department of Basic Sciences, College of Veterinary Medicine, Mississippi State University, Starkville, MS, United States
| | - Patrick M. Schlievert
- Department of Microbiology, University of Iowa, Carver College of Medicine, Iowa City, Iowa, United States of America
| | - Andreas Lengeling
- The Roslin Institute, University of Edinburgh, Easter Bush Campus, Midlothian, Scotland, United States of America
| | - Jos A. van Strijp
- Department Medical Microbiology, UMC Utrecht, Heidelberglaan 100, 3584 CX Utrecht, The Netherlands
| | - Victor J. Torres
- Department of Microbiology, New York University School of Medicine, New York, NY, United Kingdom
| | - J. Ross Fitzgerald
- The Roslin Institute, University of Edinburgh, Easter Bush Campus, Midlothian, Scotland, United States of America
- * E-mail:
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Dehydrosqualene Desaturase as a Novel Target for Anti-Virulence Therapy against Staphylococcus aureus. mBio 2017; 8:mBio.01224-17. [PMID: 28874472 PMCID: PMC5587911 DOI: 10.1128/mbio.01224-17] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Staphylococcus aureus, especially methicillin-resistant S. aureus (MRSA), is a life-threatening pathogen in hospital- and community-acquired infections. The golden-colored carotenoid pigment of S. aureus, staphyloxanthin, contributes to the resistance to reactive oxygen species (ROS) and host neutrophil-based killing. Here, we describe a novel inhibitor (NP16) of S. aureus pigment production that reduces the survival of S. aureus under oxidative stress conditions. Carotenoid components analysis, enzyme inhibition, and crtN mutational studies indicated that the molecular target of NP16 is dehydrosqualene desaturase (CrtN). S. aureus treated with NP16 showed increased susceptibility to human neutrophil killing and to innate immune clearance in a mouse infection model. Our study validates CrtN as a novel druggable target in S. aureus and presents a potent and effective lead compound for the development of virulence factor-based therapy against S. aureus. S. aureus staphyloxanthin contributes substantially to pathogenesis by interfering with host immune clearance mechanisms, but it has little impact on ex vivo survival of the bacterium. Agents blocking staphyloxanthin production may discourage the establishment and maintenance of bacterial infection without exerting selective pressure for antimicrobial resistance. Our newly discovered CrtN inhibitor, NP16, may offer an effective strategy for combating S. aureus infections.
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Chapman JR, Balasubramanian D, Tam K, Askenazi M, Copin R, Shopsin B, Torres VJ, Ueberheide BM. Using Quantitative Spectrometry to Understand the Influence of Genetics and Nutritional Perturbations On the Virulence Potential of Staphylococcus aureus. Mol Cell Proteomics 2017; 16:S15-S28. [PMID: 28196877 DOI: 10.1074/mcp.o116.065581] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2016] [Revised: 02/12/2017] [Indexed: 01/03/2023] Open
Abstract
Staphylococcus aureus (Sa) is the leading cause of a variety of bacterial infections ranging from superficial skin infections to invasive and life threatening diseases such as septic bacteremia, necrotizing pneumonia, and endocarditis. The success of Sa as a human pathogen is contributed to its ability to adapt to different environments by changing expression, production, or secretion of virulence factors. Although Sa immune evasion is well-studied, the regulation of virulence factors under different nutrient and growth conditions is still not well understood. Here, we used label-free quantitative mass spectrometry to quantify and compare the Sa exoproteins (i.e. exoproteomes) of master regulator mutants or established reference strains. Different environmental conditions were addressed by growing the bacteria in rich or minimal media at different phases of growth. We observed clear differences in the composition of the exoproteomes depending on the genetic background or growth conditions. The relative abundance of cytotoxins determined in our study correlated well with differences in cytotoxicity measured by lysis of human neutrophils. Our findings demonstrate that label-free quantitative mass spectrometry is a versatile tool for predicting the virulence of bacterial strains and highlights the importance of the experimental design for in vitro studies. Furthermore, the results indicate that label-free proteomics can be used to cluster isolates into groups with similar virulence properties, highlighting the power of label-free quantitative mass spectrometry to distinguish Sa strains.
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Affiliation(s)
| | | | | | | | - Richard Copin
- §Department of Microbiology.,‖Department of Medicine
| | - Bo Shopsin
- §Department of Microbiology.,‖Department of Medicine
| | | | - Beatrix M Ueberheide
- From the ‡Proteomics Laboratory, .,**Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York, New York 10016
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Liu Q, Yeo WS, Bae T. The SaeRS Two-Component System of Staphylococcus aureus. Genes (Basel) 2016; 7:genes7100081. [PMID: 27706107 PMCID: PMC5083920 DOI: 10.3390/genes7100081] [Citation(s) in RCA: 138] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2016] [Accepted: 09/23/2016] [Indexed: 12/20/2022] Open
Abstract
In the Gram-positive pathogenic bacterium Staphylococcus aureus, the SaeRS twocomponent system (TCS) plays a major role in controlling the production of over 20 virulence factors including hemolysins, leukocidins, superantigens, surface proteins, and proteases. The SaeRS TCS is composed of the sensor histidine kinase SaeS, response regulator SaeR, and two auxiliary proteins SaeP and SaeQ. Since its discovery in 1994, the sae locus has been studied extensively, and its contributions to staphylococcal virulence and pathogenesis have been well documented and understood; however, the molecular mechanism by which the SaeRS TCS receives and processes cognate signals is not. In this article, therefore, we review the literature focusing on the signaling mechanism and its interaction with other global regulators.
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Affiliation(s)
- Qian Liu
- Department of Laboratory Medicine, Ren Ji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai 200127, China.
| | - Won-Sik Yeo
- Department of Microbiology and Immunology, Indiana University School of Medicine-Northwest, Gary, IN 46408, USA.
| | - Taeok Bae
- Department of Microbiology and Immunology, Indiana University School of Medicine-Northwest, Gary, IN 46408, USA.
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29
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The SaeRS Two-Component System Is a Direct and Dominant Transcriptional Activator of Toxic Shock Syndrome Toxin 1 in Staphylococcus aureus. J Bacteriol 2016; 198:2732-42. [PMID: 27457715 DOI: 10.1128/jb.00425-16] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2016] [Accepted: 07/18/2016] [Indexed: 01/04/2023] Open
Abstract
UNLABELLED Toxic shock syndrome toxin 1 (TSST-1) is a Staphylococcus aureus superantigen that has been implicated in both menstrual and nonmenstrual toxic shock syndrome (TSS). Despite the important role of TSST-1 in severe human disease, a comprehensive understanding of staphylococcal regulatory factors that control TSST-1 expression remains incomplete. The S. aureus exotoxin expression (Sae) operon contains a well-characterized two-component system that regulates a number of important exotoxins in S. aureus, although regulation of TSST-1 by the Sae system has not been investigated. We generated a defined deletion mutant of the Sae histidine kinase sensor (saeS) in the prototypic menstrual TSS strain S. aureus MN8. Mutation of saeS resulted in a complete loss of TSST-1 expression. Using both luciferase reporter experiments and quantitative real-time PCR, we demonstrate that the Sae system is an important transcriptional activator of TSST-1 expression. Recombinant SaeR was able to bind directly to the tst promoter to a region containing two SaeR consensus binding sites. Although the stand-alone SarA transcriptional regulator has been shown to be both a positive and a negative regulator of TSST-1, deletion of sarA in S. aureus MN8 resulted in a dramatic overexpression of TSST-1. As expected, mutation of agr also reduced TSST-1 expression, but this phenotype appeared to be independent of Sae. A double mutation of saeS and sarA resulted in the loss of TSST-1 expression. This work indicates that the Sae system is a dominant and direct transcriptional activator that is required for expression of TSST-1. IMPORTANCE The TSST-1 superantigen is an exotoxin, produced by some strains of S. aureus, that has a clear role in both menstrual and nonmenstrual TSS. Although the well-characterized agr quorum sensing system is a known positive regulator of TSST-1, the molecular mechanisms that directly control TSST-1 expression are only partially understood. Our studies demonstrate that the Sae two-component regulatory system is a positive transcriptional regulator that binds directly to the TSST-1 promoter, and furthermore, our data suggest that Sae is required for expression of TSST-1. This work highlights how major regulatory circuits can converge to fine-tune exotoxin expression and suggests that the Sae regulatory system may be an important target for antivirulence strategies.
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Staphylococcus aureus Coordinates Leukocidin Expression and Pathogenesis by Sensing Metabolic Fluxes via RpiRc. mBio 2016; 7:mBio.00818-16. [PMID: 27329753 PMCID: PMC4916384 DOI: 10.1128/mbio.00818-16] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
UNLABELLED Staphylococcus aureus is a formidable human pathogen that uses secreted cytolytic factors to injure immune cells and promote infection of its host. Of these proteins, the bicomponent family of pore-forming leukocidins play critical roles in S. aureus pathogenesis. The regulatory mechanisms governing the expression of these toxins are incompletely defined. In this work, we performed a screen to identify transcriptional regulators involved in leukocidin expression in S. aureus strain USA300. We discovered that a metabolic sensor-regulator, RpiRc, is a potent and selective repressor of two leukocidins, LukED and LukSF-PV. Whole-genome transcriptomics, S. aureus exoprotein proteomics, and metabolomic analyses revealed that RpiRc influences the expression and production of disparate virulence factors. Additionally, RpiRc altered metabolic fluxes in the trichloroacetic acid cycle, glycolysis, and amino acid metabolism. Using mutational analyses, we confirmed and extended the observation that RpiRc signals through the accessory gene regulatory (Agr) quorum-sensing system in USA300. Specifically, RpiRc represses the rnaIII promoter, resulting in increased repressor of toxins (Rot) levels, which in turn negatively affect leukocidin expression. Inactivation of rpiRc phenocopied rot deletion and increased S. aureus killing of primary human polymorphonuclear leukocytes and the pathogenesis of bloodstream infection in vivo. Collectively, our results suggest that S. aureus senses metabolic shifts by RpiRc to differentially regulate the expression of leukocidins and to promote invasive disease. IMPORTANCE The bicomponent pore-forming leukocidins play pivotal roles in the ability of S. aureus to kill multiple host immune cells, thus enabling this pathogen to have diverse tissue- and species-tropic effects. While the mechanisms of leukocidin-host receptor interactions have been studied in detail, the regulatory aspects of leukocidin expression are less well characterized. Moreover, the expression of the leukocidins is highly modular in vitro, suggesting the presence of regulators other than the known Agr, Rot, and S. aureus exoprotein pathways. Here, we describe how RpiRc, a metabolite-sensing transcription factor, mediates the repression of two specific leukocidin genes, lukED and pvl, which in turn has complex effects on the pathogenesis of S. aureus Our findings highlight the intricacies of leukocidin regulation by S. aureus and demonstrate the involvement of factors beyond traditional virulence factor regulators.
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Bhattacharya M, Wozniak DJ, Stoodley P, Hall-Stoodley L. Prevention and treatment of Staphylococcus aureus biofilms. Expert Rev Anti Infect Ther 2015; 13:1499-516. [PMID: 26646248 DOI: 10.1586/14787210.2015.1100533] [Citation(s) in RCA: 168] [Impact Index Per Article: 18.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
S. aureus colonizes both artificial and tissue surfaces in humans causing chronic persistent infections that are difficult to cure. It is a notorious pathogen due to its antibiotic recalcitrance and phenotypic adaptability, both of which are facilitated by its ability to develop biofilms. S. aureus biofilms challenge conventional anti-infective approaches, most notably antibiotic therapy. Therefore there is an unmet need to develop and include parallel approaches that target S. aureus biofilm infections. This review discusses two broad anti-infective strategies: (1) preventative approaches (anti-biofilm surface coatings, the inclusion of biofilm-specific vaccine antigens); and (2) approaches aimed at eradicating established S. aureus biofilms, particularly those associated with implant infections. Advances in understanding the distinct nature of S. aureus biofilm development and pathogenesis have led to growing optimism in S. aureus biofilm targeted anti-infective strategies. Further research is needed however, to see the successful administration and validation of these approaches to the diverse types of infections caused by S. aureus biofilms from multiple clinical strains.
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Affiliation(s)
- Mohini Bhattacharya
- a Department of Microbiology , The Ohio State University , Columbus , OH , USA
| | - Daniel J Wozniak
- a Department of Microbiology , The Ohio State University , Columbus , OH , USA.,b Department of Microbial Infection and Immunity , The Ohio State University College of Medicine , Columbus , OH , USA.,c The Center for Microbial Interface Biology, The Ohio State University , Columbus , OH , USA
| | - Paul Stoodley
- b Department of Microbial Infection and Immunity , The Ohio State University College of Medicine , Columbus , OH , USA.,c The Center for Microbial Interface Biology, The Ohio State University , Columbus , OH , USA.,d Department of Orthopedics , The Ohio State University College of Medicine , Columbus , OH , USA.,e Department of Engineering Sciences, National Centre for Advanced Tribology at Southampton (nCATS) , University of Southampton , Southampton , UK
| | - Luanne Hall-Stoodley
- b Department of Microbial Infection and Immunity , The Ohio State University College of Medicine , Columbus , OH , USA.,c The Center for Microbial Interface Biology, The Ohio State University , Columbus , OH , USA
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Positive Regulation of Staphylococcal Enterotoxin H by Rot (Repressor of Toxin) Protein and Its Importance in Clonal Complex 81 Subtype 1 Lineage-Related Food Poisoning. Appl Environ Microbiol 2015; 81:7782-90. [PMID: 26341202 DOI: 10.1128/aem.01936-15] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2015] [Accepted: 08/22/2015] [Indexed: 11/20/2022] Open
Abstract
We previously demonstrated the clonal complex 81 (CC81) subtype 1 lineage is the major staphylococcal food poisoning (SFP)-associated lineage in Japan (Y. Sato'o et al., J Clin Microbiol 52:2637-2640, 2014, http://dx.doi.org/10.1128/JCM.00661-14). Strains of this lineage produce staphylococcal enterotoxin H (SEH) in addition to SEA. However, an evaluation of the risk for the recently reported SEH has not been sufficiently conducted. We first searched for staphylococcal enterotoxin (SE) genes and SE proteins in milk samples that caused a large SFP outbreak in Japan. Only SEA and SEH were detected, while there were several SE genes detected in the samples. We next designed an experimental model using a meat product to assess the productivity of SEs and found that only SEA and SEH were detectably produced in situ. Therefore, we investigated the regulation of SEH production using a CC81 subtype 1 isolate. Through mutant analysis of global regulators, we found the repressor of toxin (Rot) functioned oppositely as a stimulator of SEH production. SEA production was not affected by Rot. seh mRNA expression correlated with rot both in media and on the meat product, and the Rot protein was shown to directly bind to the seh promoter. The seh promoter sequence was predicted to form a loop structure and to hide the RNA polymerase binding sequences. We propose Rot binds to the promoter sequence of seh and unfolds the secondary structure that may lead the RNA polymerase to bind the promoter, and then seh mRNA transcription begins. This alternative Rot regulation for SEH may contribute to sufficient toxin production by the CC81 subtype 1 lineage in foods to induce SFP.
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33
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Andrey DO, Jousselin A, Villanueva M, Renzoni A, Monod A, Barras C, Rodriguez N, Kelley WL. Impact of the Regulators SigB, Rot, SarA and sarS on the Toxic Shock Tst Promoter and TSST-1 Expression in Staphylococcus aureus. PLoS One 2015; 10:e0135579. [PMID: 26275216 PMCID: PMC4537247 DOI: 10.1371/journal.pone.0135579] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2014] [Accepted: 07/24/2015] [Indexed: 12/21/2022] Open
Abstract
Staphylococcus aureus is an important pathogen manifesting virulence through diverse disease forms, ranging from acute skin infections to life-threatening bacteremia or systemic toxic shock syndromes. In the latter case, the prototypical superantigen is TSST-1 (Toxic Shock Syndrome Toxin 1), encoded by tst(H), and carried on a mobile genetic element that is not present in all S. aureus strains. Transcriptional regulation of tst is only partially understood. In this study, we dissected the role of sarA, sarS (sarH1), RNAIII, rot, and the alternative stress sigma factor sigB (σB). By examining tst promoter regulation predominantly in the context of its native sequence within the SaPI1 pathogenicity island of strain RN4282, we discovered that σB emerged as a particularly important tst regulator. We did not detect a consensus σB site within the tst promoter, and thus the effect of σB is likely indirect. We found that σB strongly repressed the expression of the toxin via at least two distinct regulatory pathways dependent upon sarA and agr. Furthermore rot, a member of SarA family, was shown to repress tst expression when overexpressed, although its deletion had no consistent measurable effect. We could not find any detectable effect of sarS, either by deletion or overexpression, suggesting that this regulator plays a minimal role in TSST-1 expression except when combined with disruption of sarA. Collectively, our results extend our understanding of complex multifactorial regulation of tst, revealing several layers of negative regulation. In addition to environmental stimuli thought to impact TSST-1 production, these findings support a model whereby sporadic mutation in a few key negative regulators can profoundly affect and enhance TSST-1 expression.
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Affiliation(s)
- Diego O. Andrey
- Service of Infectious Diseases, University Hospital and Medical School of Geneva, 4 rue Gabrielle-Perret-Gentil, CH-1211 Geneva 14, Switzerland
| | - Ambre Jousselin
- Department of Microbiology and Molecular Medicine, University Hospital and Medical School of Geneva, 1 rue Michel-Servet, CH-1211 Geneva, Switzerland
| | - Maite Villanueva
- Department of Microbiology and Molecular Medicine, University Hospital and Medical School of Geneva, 1 rue Michel-Servet, CH-1211 Geneva, Switzerland
| | - Adriana Renzoni
- Service of Infectious Diseases, University Hospital and Medical School of Geneva, 4 rue Gabrielle-Perret-Gentil, CH-1211 Geneva 14, Switzerland
| | - Antoinette Monod
- Service of Infectious Diseases, University Hospital and Medical School of Geneva, 4 rue Gabrielle-Perret-Gentil, CH-1211 Geneva 14, Switzerland
| | - Christine Barras
- Service of Infectious Diseases, University Hospital and Medical School of Geneva, 4 rue Gabrielle-Perret-Gentil, CH-1211 Geneva 14, Switzerland
| | - Natalia Rodriguez
- Department of Microbiology and Molecular Medicine, University Hospital and Medical School of Geneva, 1 rue Michel-Servet, CH-1211 Geneva, Switzerland
| | - William L. Kelley
- Department of Microbiology and Molecular Medicine, University Hospital and Medical School of Geneva, 1 rue Michel-Servet, CH-1211 Geneva, Switzerland
- * E-mail:
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Abstract
PURPOSE OF REVIEW Methicillin-resistant strains of the important human pathogen Staphylococcus aureus pose a significant public health threat in the community, as they are easily transmitted, especially prone to cause invasive disease, and infect otherwise healthy individuals. The mechanistic basis for the ability of these organisms to evade the innate immune responses remains incompletely defined. RECENT FINDINGS The success of pathogens such as S. aureus rests, in part, on their capacity to overcome neutrophil-mediated host defense to establish infection and cause human disease. S. aureus has the potential to thwart effective neutrophil chemotaxis, and phagocytosis, and succeeds in evading killing by neutrophils. Furthermore, S. aureus surviving within neutrophils promotes neutrophil cytolysis, with release of host-derived molecules that promote local inflammation. Here, we provide a brief overview of our understanding of the mechanisms by which S. aureus - including methicillin-resistant S. aureus - avoids neutrophil-mediated host defense and causes disease. SUMMARY Understanding the molecular mechanisms by which S. aureus avoids neutrophil-mediated responses and initiates signaling cascades that culminate in neutrophil lysis will provide insights prerequisite to the development of novel targets for treating staphylococcal infections.
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Melehani JH, James DBA, DuMont AL, Torres VJ, Duncan JA. Staphylococcus aureus Leukocidin A/B (LukAB) Kills Human Monocytes via Host NLRP3 and ASC when Extracellular, but Not Intracellular. PLoS Pathog 2015; 11:e1004970. [PMID: 26069969 PMCID: PMC4466499 DOI: 10.1371/journal.ppat.1004970] [Citation(s) in RCA: 95] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2014] [Accepted: 05/22/2015] [Indexed: 12/27/2022] Open
Abstract
Staphylococcus aureus infections are a growing health burden worldwide, and paramount to this bacterium’s pathogenesis is the production of virulence factors, including pore-forming leukotoxins. Leukocidin A/B (LukAB) is a recently discovered toxin that kills primary human phagocytes, though the underlying mechanism of cell death is not understood. We demonstrate here that LukAB is a major contributor to the death of human monocytes. Using a variety of in vitro and ex vivo intoxication and infection models, we found that LukAB activates Caspase 1, promotes IL-1β secretion and induces necrosis in human monocytes. Using THP1 cells as a model for human monocytes, we found that the inflammasome components NLRP3 and ASC are required for LukAB-mediated IL-1β secretion and necrotic cell death. S. aureus was shown to kill human monocytes in a LukAB dependent manner under both extracellular and intracellular ex vivo infection models. Although LukAB-mediated killing of THP1 monocytes from extracellular S. aureus requires ASC, NLRP3 and the LukAB-receptor CD11b, LukAB-mediated killing from phagocytosed S. aureus is independent of ASC or NLRP3, but dependent on CD11b. Altogether, this study provides insight into the nature of LukAB-mediated killing of human monocytes. The discovery that S. aureus LukAB provokes differential host responses in a manner dependent on the cellular contact site is critical for the development of anti-infective/anti-inflammatory therapies that target the NLRP3 inflammasome. Staphylococcus aureus infections are becoming increasingly common, aggressive, and difficult to manage clinically. S. aureus produces a number of pore-forming toxins that target and kill immune cells. In this study, we demonstrate that LukAB is primarily responsible for S. aureus-mediated targeting and killing of human monocytes. We show that the NLRP3-ASC inflammasome, a sensor of cell membrane damage and trigger of inflammation, is critical for this response. S. aureus uses LukAB to kill immune cells both through external interactions (LukAB on the cell surface) and through internal interactions (LukAB secretion after S. aureus is engulfed by the immune cell). Interestingly, we show that the mechanism by which LukAB kills immune cells in these two settings differs. This is the first report of a S. aureus toxin manipulating unique immune signaling pathways depending on the cellular site of contact. Understanding the multitude of ways by which S. aureus evades the immune response is critical for our ability to treat infections with this pathogen.
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Affiliation(s)
- Jason H. Melehani
- Department of Pharmacology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
| | - David B. A. James
- Department of Microbiology, New York University School of Medicine, New York, New York, United States of America
| | - Ashley L. DuMont
- Department of Microbiology, New York University School of Medicine, New York, New York, United States of America
| | - Victor J. Torres
- Department of Microbiology, New York University School of Medicine, New York, New York, United States of America
- * E-mail: (VJT); (JAD)
| | - Joseph A. Duncan
- Department of Pharmacology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
- Department of Medicine, Division of Infectious Diseases, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
- * E-mail: (VJT); (JAD)
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36
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The bicomponent pore-forming leucocidins of Staphylococcus aureus. Microbiol Mol Biol Rev 2015; 78:199-230. [PMID: 24847020 DOI: 10.1128/mmbr.00055-13] [Citation(s) in RCA: 192] [Impact Index Per Article: 21.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The ability to produce water-soluble proteins with the capacity to oligomerize and form pores within cellular lipid bilayers is a trait conserved among nearly all forms of life, including humans, single-celled eukaryotes, and numerous bacterial species. In bacteria, some of the most notable pore-forming molecules are protein toxins that interact with mammalian cell membranes to promote lysis, deliver effectors, and modulate cellular homeostasis. Of the bacterial species capable of producing pore-forming toxic molecules, the Gram-positive pathogen Staphylococcus aureus is one of the most notorious. S. aureus can produce seven different pore-forming protein toxins, all of which are believed to play a unique role in promoting the ability of the organism to cause disease in humans and other mammals. The most diverse of these pore-forming toxins, in terms of both functional activity and global representation within S. aureus clinical isolates, are the bicomponent leucocidins. From the first description of their activity on host immune cells over 100 years ago to the detailed investigations of their biochemical function today, the leucocidins remain at the forefront of S. aureus pathogenesis research initiatives. Study of their mode of action is of immediate interest in the realm of therapeutic agent design as well as for studies of bacterial pathogenesis. This review provides an updated perspective on our understanding of the S. aureus leucocidins and their function, specificity, and potential as therapeutic targets.
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Mootz JM, Benson MA, Heim CE, Crosby HA, Kavanaugh JS, Dunman PM, Kielian T, Torres VJ, Horswill AR. Rot is a key regulator of Staphylococcus aureus biofilm formation. Mol Microbiol 2015; 96:388-404. [PMID: 25612137 DOI: 10.1111/mmi.12943] [Citation(s) in RCA: 59] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/19/2015] [Indexed: 01/28/2023]
Abstract
Staphylococcus aureus is a significant cause of chronic biofilm infections on medical implants. We investigated the biofilm regulatory cascade and discovered that the repressor of toxins (Rot) is part of this pathway. A USA300 community-associated methicillin-resistant S. aureus strain deficient in Rot was unable to form a biofilm using multiple different assays, and we found rot mutants in other strain lineages were also biofilm deficient. By performing a global analysis of transcripts and protein production controlled by Rot, we observed that all the secreted protease genes were up-regulated in a rot mutant, and we hypothesized that this regulation could be responsible for the biofilm phenotype. To investigate this question, we determined that Rot bound to the protease promoters, and we observed that activity levels of these enzymes, in particular the cysteine proteases, were increased in a rot mutant. By inactivating these proteases, biofilm capacity was restored to the mutant, demonstrating they are responsible for the biofilm negative phenotype. Finally, we tested the rot mutant in a mouse catheter model of biofilm infection and observed a significant reduction in biofilm burden. Thus S. aureus uses the transcription factor Rot to repress secreted protease levels in order to build a biofilm.
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Affiliation(s)
- Joe M Mootz
- Department of Microbiology, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, IA, 52242, USA
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38
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The Role of Two-Component Signal Transduction Systems in Staphylococcus aureus Virulence Regulation. Curr Top Microbiol Immunol 2015; 409:145-198. [PMID: 26728068 DOI: 10.1007/82_2015_5019] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Staphylococcus aureus is a versatile, opportunistic human pathogen that can asymptomatically colonize a human host but can also cause a variety of cutaneous and systemic infections. The ability of S. aureus to adapt to such diverse environments is reflected in the presence of complex regulatory networks fine-tuning metabolic and virulence gene expression. One of the most widely distributed mechanisms is the two-component signal transduction system (TCS) which allows a pathogen to alter its gene expression profile in response to environmental stimuli. The simpler TCSs consist of only a transmembrane histidine kinase (HK) and a cytosolic response regulator. S. aureus encodes a total of 16 conserved pairs of TCSs that are involved in diverse signalling cascades ranging from global virulence gene regulation (e.g. quorum sensing by the Agr system), the bacterial response to antimicrobial agents, cell wall metabolism, respiration and nutrient sensing. These regulatory circuits are often interconnected and affect each other's expression, thus fine-tuning staphylococcal gene regulation. This manuscript gives an overview of the current knowledge of staphylococcal environmental sensing by TCS and its influence on virulence gene expression and virulence itself. Understanding bacterial gene regulation by TCS can give major insights into staphylococcal pathogenicity and has important implications for knowledge-based drug design and vaccine formulation.
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39
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Gastrointestinal dissemination and transmission of Staphylococcus aureus following bacteremia. Infect Immun 2014; 83:372-8. [PMID: 25385792 DOI: 10.1128/iai.02272-14] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Mutations that alter virulence and antibiotic susceptibility arise and persist during Staphylococcus aureus bacteremia. However, an experimental system demonstrating transmission following bacteremia has been lacking, and thus implications of within-host adaptation for between-host transmission are unknown. We report that S. aureus disseminates to the gastrointestinal tract of mice following intravenous injection and readily transmits to cohoused naive mice. Both intestinal dissemination and transmission were linked to the production of virulence factors based on gene deletion studies of the sae and agr two-component systems. Furthermore, antimicrobial selection for antibiotic-resistant S. aureus displaced susceptible S. aureus from the intestine of infected hosts, which led to the preferential transmission and dominance of antibiotic-resistant bacteria among cohoused untreated mice. These findings establish an animal model to investigate gastrointestinal dissemination and transmission of S. aureus and suggest that adaptation during the course of systemic infection has implications beyond the level of a single host.
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40
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Velarde JJ, Ashbaugh M, Wessels MR. The human antimicrobial peptide LL-37 binds directly to CsrS, a sensor histidine kinase of group A Streptococcus, to activate expression of virulence factors. J Biol Chem 2014; 289:36315-24. [PMID: 25378408 DOI: 10.1074/jbc.m114.605394] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Group A Streptococcus (GAS) responds to subinhibitory concentrations of LL-37 by up-regulation of virulence factors through the CsrRS (CovRS) two-component system. The signaling mechanism, however, is unclear. To determine whether LL-37 signaling reflects specific binding to CsrS or rather a nonspecific response to LL-37-mediated membrane damage, we tested LL-37 fragments for CsrRS signaling and for GAS antimicrobial activity. We identified a 10-residue fragment (RI-10) of LL-37 as the minimal peptide that retains the ability to signal increased expression of GAS virulence factors, yet it has no detectable antimicrobial activity against GAS. Substitution of individual key amino acids in RI-10 reduced or abrogated signaling. These data do not support the hypothesis that CsrS detects LL-37-induced damage to the bacterial cell membrane but rather suggest that LL-37 signaling is mediated by a direct interaction with CsrS. To test whether LL-37 binds to CsrS, we used the purified CsrS extracellular domain to pull down LL-37 in vitro, a result that provides further evidence that LL-37 binds to CsrS. The dissociation of CsrS-mediated signaling from membrane damage by LL-37 fragments together with in vitro evidence for a direct LL-37-CsrS binding interaction constitute compelling evidence that signal transduction by LL-37 through CsrS reflects a direct ligand/receptor interaction.
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Affiliation(s)
- Jorge J Velarde
- From the Division of Infectious Diseases, Boston Children's Hospital and Department of Pediatrics, Harvard Medical School, Boston, Massachusetts 02115
| | - Melissa Ashbaugh
- From the Division of Infectious Diseases, Boston Children's Hospital and Department of Pediatrics, Harvard Medical School, Boston, Massachusetts 02115
| | - Michael R Wessels
- From the Division of Infectious Diseases, Boston Children's Hospital and Department of Pediatrics, Harvard Medical School, Boston, Massachusetts 02115
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41
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Hepburn L, Prajsnar TK, Klapholz C, Moreno P, Loynes CA, Ogryzko NV, Brown K, Schiebler M, Hegyi K, Antrobus R, Hammond KL, Connolly J, Ochoa B, Bryant C, Otto M, Surewaard B, Seneviratne SL, Grogono DM, Cachat J, Ny T, Kaser A, Török ME, Peacock SJ, Holden M, Blundell T, Wang L, Ligoxygakis P, Minichiello L, Woods CG, Foster SJ, Renshaw SA, Floto RA. Innate immunity. A Spaetzle-like role for nerve growth factor β in vertebrate immunity to Staphylococcus aureus. Science 2014; 346:641-646. [PMID: 25359976 PMCID: PMC4255479 DOI: 10.1126/science.1258705] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Many key components of innate immunity to infection are shared between Drosophila and humans. However, the fly Toll ligand Spaetzle is not thought to have a vertebrate equivalent. We have found that the structurally related cystine-knot protein, nerve growth factor β (NGFβ), plays an unexpected Spaetzle-like role in immunity to Staphylococcus aureus infection in chordates. Deleterious mutations of either human NGFβ or its high-affinity receptor tropomyosin-related kinase receptor A (TRKA) were associated with severe S. aureus infections. NGFβ was released by macrophages in response to S. aureus exoproteins through activation of the NOD-like receptors NLRP3 and NLRP4 and enhanced phagocytosis and superoxide-dependent killing, stimulated proinflammatory cytokine production, and promoted calcium-dependent neutrophil recruitment. TrkA knockdown in zebrafish increased susceptibility to S. aureus infection, confirming an evolutionarily conserved role for NGFβ-TRKA signaling in pathogen-specific host immunity.
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Affiliation(s)
- Lucy Hepburn
- Cambridge Institute for Medical Research, University of Cambridge, UK
- Department of Medicine, University of Cambridge, UK
| | - Tomasz K. Prajsnar
- Krebs Institute, University of Sheffield, Western Bank, Sheffield, S10 2TN, UK
- Department of Molecular Biology and Biotechnology, University of Sheffield, Western Bank, Sheffield, S10 2TN, UK
- Bateson Centre, University of Sheffield, Western Bank, Sheffield, S10 2TN, UK
| | - Catherine Klapholz
- Cambridge Institute for Medical Research, University of Cambridge, UK
- Department of Medicine, University of Cambridge, UK
| | - Pablo Moreno
- Cambridge Institute for Medical Research, University of Cambridge, UK
| | - Catherine A. Loynes
- Bateson Centre, University of Sheffield, Western Bank, Sheffield, S10 2TN, UK
- Department of Infection and Immunity, University of Sheffield, Western Bank, Sheffield, S10 2TN, UK
| | - Nikolay V. Ogryzko
- Bateson Centre, University of Sheffield, Western Bank, Sheffield, S10 2TN, UK
| | - Karen Brown
- Cambridge Institute for Medical Research, University of Cambridge, UK
- Department of Medicine, University of Cambridge, UK
- Cambridge Centre for Lung Infection, Papworth Hospital, Cambridge, UK
| | - Mark Schiebler
- Cambridge Institute for Medical Research, University of Cambridge, UK
- Department of Medicine, University of Cambridge, UK
| | - Krisztina Hegyi
- Cambridge Institute for Medical Research, University of Cambridge, UK
- Department of Medicine, University of Cambridge, UK
| | - Robin Antrobus
- Cambridge Institute for Medical Research, University of Cambridge, UK
| | - Katherine L. Hammond
- Bateson Centre, University of Sheffield, Western Bank, Sheffield, S10 2TN, UK
- Department of Infection and Immunity, University of Sheffield, Western Bank, Sheffield, S10 2TN, UK
| | - John Connolly
- Krebs Institute, University of Sheffield, Western Bank, Sheffield, S10 2TN, UK
- Department of Molecular Biology and Biotechnology, University of Sheffield, Western Bank, Sheffield, S10 2TN, UK
| | | | - Clare Bryant
- Department of Veterinary Medicine, University of Cambridge, UK
| | - Michael Otto
- Laboratory of Human Bacterial Pathogenesis NIAID, NIH, Bethesda USA
| | - Bas Surewaard
- Dept of Medical Microbiology, University Medical Centre, Utrecht, Netherlands
| | | | - Dorothy M. Grogono
- Department of Medicine, University of Cambridge, UK
- Cambridge Centre for Lung Infection, Papworth Hospital, Cambridge, UK
| | - Julien Cachat
- Dept. of Pathology and Immunology, Geneva University, Switzerland
| | - Tor Ny
- Dept. of Medical Biochemistry and Biophysics, Umea University, Sweden
| | - Arthur Kaser
- Department of Medicine, University of Cambridge, UK
| | | | - Sharon J. Peacock
- Department of Medicine, University of Cambridge, UK
- Wellcome Trust Sanger Institute, Hinxton, UK
| | | | - Tom Blundell
- Department of Biochemistry, University of Cambridge, UK
| | - Lihui Wang
- Biochemistry Department, Oxford University. UK
| | | | | | - C. Geoff Woods
- Cambridge Institute for Medical Research, University of Cambridge, UK
- Department of Medical Genetics, University of Cambridge, UK
| | - Simon J. Foster
- Krebs Institute, University of Sheffield, Western Bank, Sheffield, S10 2TN, UK
- Department of Molecular Biology and Biotechnology, University of Sheffield, Western Bank, Sheffield, S10 2TN, UK
| | - Stephen A. Renshaw
- Krebs Institute, University of Sheffield, Western Bank, Sheffield, S10 2TN, UK
- Bateson Centre, University of Sheffield, Western Bank, Sheffield, S10 2TN, UK
- Department of Infection and Immunity, University of Sheffield, Western Bank, Sheffield, S10 2TN, UK
| | - R. Andres Floto
- Cambridge Institute for Medical Research, University of Cambridge, UK
- Department of Medicine, University of Cambridge, UK
- Cambridge Centre for Lung Infection, Papworth Hospital, Cambridge, UK
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42
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Structure-based functional characterization of repressor of toxin (Rot), a central regulator of Staphylococcus aureus virulence. J Bacteriol 2014; 197:188-200. [PMID: 25331435 DOI: 10.1128/jb.02317-14] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Staphylococcus aureus is responsible for a large number of diverse infections worldwide. In order to support its pathogenic lifestyle, S. aureus has to regulate the expression of virulence factors in a coordinated fashion. One of the central regulators of the S. aureus virulence regulatory networks is the transcription factor repressor of toxin (Rot). Rot plays a key role in regulating S. aureus virulence through activation or repression of promoters that control expression of a large number of critical virulence factors. However, the mechanism by which Rot mediates gene regulation has remained elusive. Here, we have determined the crystal structure of Rot and used this information to probe the contribution made by specific residues to Rot function. Rot was found to form a dimer, with each monomer harboring a winged helix-turn-helix (WHTH) DNA-binding motif. Despite an overall acidic pI, the asymmetric electrostatic charge profile suggests that Rot can orient the WHTH domain to bind DNA. Structure-based site-directed mutagenesis studies demonstrated that R(91), at the tip of the wing, plays an important role in DNA binding, likely through interaction with the minor groove. We also found that Y(66), predicted to bind within the major groove, contributes to Rot interaction with target promoters. Evaluation of Rot binding to different activated and repressed promoters revealed that certain mutations on Rot exhibit promoter-specific effects, suggesting for the first time that Rot differentially interacts with target promoters. This work provides insight into a precise mechanism by which Rot controls virulence factor regulation in S. aureus.
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43
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Zhu Y, Fan X, Zhang X, Jiang X, Niu L, Teng M, Li X. Structure of Rot, a global regulator of virulence genes in Staphylococcus aureus. ACTA ACUST UNITED AC 2014; 70:2467-76. [PMID: 25195759 DOI: 10.1107/s1399004714015326] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2014] [Accepted: 06/30/2014] [Indexed: 12/13/2022]
Abstract
Staphylococcus aureus is a highly versatile pathogen that can infect human tissue by producing a large arsenal of virulence factors that are tightly regulated by a complex regulatory network. Rot, which shares sequence similarity with SarA homologues, is a global regulator that regulates numerous virulence genes. However, the recognition model of Rot for the promoter region of target genes and the putative regulation mechanism remain elusive. In this study, the 1.77 Å resolution X-ray crystal structure of Rot is reported. The structure reveals that two Rot molecules form a compact homodimer, each of which contains a typical helix-turn-helix module and a β-hairpin motif connected by a flexible loop. Fluorescence polarization results indicate that Rot preferentially recognizes AT-rich dsDNA with ~30-base-pair nucleotides and that the conserved positively charged residues on the winged-helix motif are vital for binding to the AT-rich dsDNA. It is proposed that the DNA-recognition model of Rot may be similar to that of SarA, SarR and SarS, in which the helix-turn-helix motifs of each monomer interact with the major grooves of target dsDNA and the winged motifs contact the minor grooves. Interestingly, the structure shows that Rot adopts a novel dimerization model that differs from that of other SarA homologues. As expected, perturbation of the dimer interface abolishes the dsDNA-binding ability of Rot, suggesting that Rot functions as a dimer. In addition, the results have been further confirmed in vivo by measuring the transcriptional regulation of α-toxin, a major virulence factor produced by most S. aureus strains.
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Affiliation(s)
- Yuwei Zhu
- Hefei National Laboratory for Physical Sciences at Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230026, People's Republic of China
| | - Xiaojiao Fan
- Hefei National Laboratory for Physical Sciences at Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230026, People's Republic of China
| | - Xu Zhang
- Department of Microbiology and Immunology, School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230026, People's Republic of China
| | - Xuguang Jiang
- Hefei National Laboratory for Physical Sciences at Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230026, People's Republic of China
| | - Liwen Niu
- Hefei National Laboratory for Physical Sciences at Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230026, People's Republic of China
| | - Maikun Teng
- Hefei National Laboratory for Physical Sciences at Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230026, People's Republic of China
| | - Xu Li
- Hefei National Laboratory for Physical Sciences at Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230026, People's Republic of China
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44
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Benson MA, Ohneck EA, Ryan C, Alonzo F, Smith H, Narechania A, Kolokotronis SO, Satola SW, Uhlemann AC, Sebra R, Deikus G, Shopsin B, Planet PJ, Torres VJ. Evolution of hypervirulence by a MRSA clone through acquisition of a transposable element. Mol Microbiol 2014; 93:664-81. [PMID: 24962815 PMCID: PMC4127135 DOI: 10.1111/mmi.12682] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/19/2014] [Indexed: 01/17/2023]
Abstract
Staphylococcus aureus has evolved as a pathogen that causes a range of diseases in humans. There are two dominant modes of evolution thought to explain most of the virulence differences between strains. First, virulence genes may be acquired from other organisms. Second, mutations may cause changes in the regulation and expression of genes. Here we describe an evolutionary event in which transposition of an IS element has a direct impact on virulence gene regulation resulting in hypervirulence. Whole-genome analysis of a methicillin-resistant S. aureus (MRSA) strain USA500 revealed acquisition of a transposable element (IS256) that is absent from close relatives of this strain. Of the multiple copies of IS256 found in the USA500 genome, one was inserted in the promoter sequence of repressor of toxins (Rot), a master transcriptional regulator responsible for the expression of virulence factors in S. aureus. We show that insertion into the rot promoter by IS256 results in the derepression of cytotoxin expression and increased virulence. Taken together, this work provides new insight into evolutionary strategies by which S. aureus is able to modify its virulence properties and demonstrates a novel mechanism by which horizontal gene transfer directly impacts virulence through altering toxin regulation.
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Affiliation(s)
- Meredith A. Benson
- Department of Microbiology, New York University School of Medicine, New York, New York, U.S.A
| | - Elizabeth A. Ohneck
- Department of Microbiology, New York University School of Medicine, New York, New York, U.S.A
| | - Chanelle Ryan
- Department of Medicine, Pediatric Infectious Disease Division, Columbia University, New York, New York, U.S.A
| | - Francis Alonzo
- Department of Microbiology, New York University School of Medicine, New York, New York, U.S.A
| | - Hannah Smith
- Department of Medicine, Pediatric Infectious Disease Division, Columbia University, New York, New York, U.S.A
| | - Apurva Narechania
- Sackler Institute for Comparative Genomics, American Museum of Natural History, New York, NY, 10024, USA
| | | | - Sarah W. Satola
- Department of Medicine, Division of Infectious Diseases, Emory University, Atlanta, GA, U.S.A
- Atlanta Veterans Affairs Medical Center, Decatur, GA, U.S.A
| | - Anne-Catrin Uhlemann
- Department of Medicine, Division of Infectious Diseases, Columbia University Medical Center, New York, NY, U.S.A
| | - Robert Sebra
- Genome Center, Mount Sinai Hospital, New York, New York, U.S.A
| | - Gintaras Deikus
- Genome Center, Mount Sinai Hospital, New York, New York, U.S.A
| | - Bo Shopsin
- Department of Microbiology, New York University School of Medicine, New York, New York, U.S.A
- Department of Medicine, Division of Infectious Diseases, New York University School of Medicine, New York, New York, U.S.A
| | - Paul J. Planet
- Department of Medicine, Pediatric Infectious Disease Division, Columbia University, New York, New York, U.S.A
- Sackler Institute for Comparative Genomics, American Museum of Natural History, New York, NY, 10024, USA
| | - Victor J. Torres
- Department of Microbiology, New York University School of Medicine, New York, New York, U.S.A
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45
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Carroll RK, Rivera FE, Cavaco CK, Johnson GM, Martin D, Shaw LN. The lone S41 family C-terminal processing protease in Staphylococcus aureus is localized to the cell wall and contributes to virulence. MICROBIOLOGY-SGM 2014; 160:1737-1748. [PMID: 24928312 DOI: 10.1099/mic.0.079798-0] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Staphylococcus aureus is a versatile pathogen of humans and a continued public health concern due to the rise and spread of multidrug-resistant strains. As part of an ongoing investigation into the pathogenic mechanisms of this organism we previously demonstrated that an intracellular N-terminal processing protease is required for S. aureus virulence. Following on from this, here we examine the role of CtpA, the lone C-terminal processing protease of S. aureus. CtpA, a member of the S41 family, is a serine protease whose homologues in Gram-negative bacteria have been implicated in a range of biological functions, including pathogenesis. We demonstrate that S. aureus CtpA is localized to the bacterial cell wall and expression of the ctpA gene is maximal upon exposure to conditions encountered during infection. Disruption of the ctpA gene leads to decreased heat tolerance and increased sensitivity when exposed to components of the host immune system. Finally we demonstrate that the ctpA(-) mutant strain is attenuated for virulence in a murine model of infection. Our results represent the first characterization of a C-terminal processing protease in a pathogenic Gram-positive bacterium and show that it plays a critical role during infection.
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Affiliation(s)
- Ronan K Carroll
- Department of Cell Biology, Microbiology & Molecular Biology, University of South Florida, Tampa, FL, USA
| | - Frances E Rivera
- Department of Cell Biology, Microbiology & Molecular Biology, University of South Florida, Tampa, FL, USA
| | - Courtney K Cavaco
- Department of Cell Biology, Microbiology & Molecular Biology, University of South Florida, Tampa, FL, USA
| | - Grant M Johnson
- Department of Cell Biology, Microbiology & Molecular Biology, University of South Florida, Tampa, FL, USA
| | - David Martin
- Department of Cell Biology, Microbiology & Molecular Biology, University of South Florida, Tampa, FL, USA
| | - Lindsey N Shaw
- Department of Cell Biology, Microbiology & Molecular Biology, University of South Florida, Tampa, FL, USA
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46
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Bröker BM, Holtfreter S, Bekeredjian-Ding I. Immune control of Staphylococcus aureus – Regulation and counter-regulation of the adaptive immune response. Int J Med Microbiol 2014; 304:204-14. [DOI: 10.1016/j.ijmm.2013.11.008] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
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47
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The δ subunit of RNA polymerase guides promoter selectivity and virulence in Staphylococcus aureus. Infect Immun 2014; 82:1424-35. [PMID: 24491578 DOI: 10.1128/iai.01508-14] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
In Gram-positive bacteria, and particularly the Firmicutes, the DNA-dependent RNA polymerase (RNAP) complex contains an additional subunit, termed the δ factor, or RpoE. This enigmatic protein has been studied for more than 30 years for various organisms, but its function is still not well understood. In this study, we investigated its role in the major human pathogen Staphylococcus aureus. We showed conservation of important structural regions of RpoE in S. aureus and other species and demonstrated binding to core RNAP that is mediated by the β and/or β' subunits. To identify the impact of the δ subunit on transcription, we performed transcriptome sequencing (RNA-seq) analysis and observed 191 differentially expressed genes in the rpoE mutant. Ontological analysis revealed, quite strikingly, that many of the downregulated genes were known virulence factors, while several mobile genetic elements (SaPI5 and prophage SA3usa) were strongly upregulated. Phenotypically, the rpoE mutant had decreased accumulation and/or activity of a number of key virulence factors, including alpha toxin, secreted proteases, and Panton-Valentine leukocidin (PVL). We further observed significantly decreased survival of the mutant in whole human blood, increased phagocytosis by human leukocytes, and impaired virulence in a murine model of infection. Collectively, our results demonstrate that the δ subunit of RNAP is a critical component of the S. aureus transcription machinery and plays an important role during infection.
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Cassat JE, Hammer ND, Campbell JP, Benson MA, Perrien DS, Mrak LN, Smeltzer MS, Torres VJ, Skaar EP. A secreted bacterial protease tailors the Staphylococcus aureus virulence repertoire to modulate bone remodeling during osteomyelitis. Cell Host Microbe 2013; 13:759-72. [PMID: 23768499 DOI: 10.1016/j.chom.2013.05.003] [Citation(s) in RCA: 155] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2013] [Revised: 04/21/2013] [Accepted: 04/30/2013] [Indexed: 11/29/2022]
Abstract
Osteomyelitis is a common manifestation of invasive Staphylococcus aureus infection. Pathogen-induced bone destruction limits antimicrobial penetration to the infectious focus and compromises treatment of osteomyelitis. To investigate mechanisms of S. aureus-induced bone destruction, we developed a murine model of osteomyelitis. Microcomputed tomography of infected femurs revealed that S. aureus triggers profound alterations in bone turnover. The bacterial regulatory locus sae was found to be critical for osteomyelitis pathogenesis, as Sae-regulated factors promote pathologic bone remodeling and intraosseous bacterial survival. Exoproteome analyses revealed the Sae-regulated protease aureolysin as a major determinant of the S. aureus secretome and identified the phenol-soluble modulins as aureolysin-degraded, osteolytic peptides that trigger osteoblast cell death and bone destruction. These studies establish a murine model for pathogen-induced bone remodeling, define Sae as critical for osteomyelitis pathogenesis, and identify protease-dependent exoproteome remodeling as a major determinant of the staphylococcal virulence repertoire.
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Affiliation(s)
- James E Cassat
- Department of Pediatrics, Division of Pediatric Infectious Diseases, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
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Role of Rot in bacterial autolysis regulation of Staphylococcus aureus NCTC8325. Res Microbiol 2013; 164:695-700. [DOI: 10.1016/j.resmic.2013.06.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2013] [Accepted: 05/27/2013] [Indexed: 02/02/2023]
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Staphylococcus aureus elaborates leukocidin AB to mediate escape from within human neutrophils. Infect Immun 2013; 81:1830-41. [PMID: 23509138 DOI: 10.1128/iai.00095-13] [Citation(s) in RCA: 107] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Methicillin-resistant Staphylococcus aureus (MRSA) strains of the pulsed-field type USA300 are primarily responsible for the current community-associated epidemic of MRSA infections in the United States. The success of USA300 is partly attributed to the ability of the pathogen to avoid destruction by human neutrophils (polymorphonuclear leukocytes [PMNs]), which are crucial to the host immune response to S. aureus infection. In this work, we investigated the contribution of bicomponent pore-forming toxins to the ability of USA300 to withstand attack from primary human PMNs. We demonstrate that in vitro growth conditions influence the expression, production, and availability of leukotoxins by USA300, which in turn impact the cytotoxic potential of this clone toward PMNs. Interestingly, we also found that upon exposure to PMNs, USA300 preferentially activates the promoter of the lukAB operon, which encodes the recently identified leukocidin AB (LukAB). LukAB elaborated by extracellular S. aureus forms pores in the plasma membrane of PMNs, leading to PMN lysis, highlighting a contribution of LukAB to USA300 virulence. We now show that LukAB also facilitates the escape of bacteria engulfed within PMNs, in turn enabling the replication and outgrowth of S. aureus. Together, these results suggest that upon encountering PMNs S. aureus induces the production of LukAB, which serves as an extra- and intracellular weapon to protect the bacterium from destruction by human PMNs.
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