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Kempher ML, Shadid TM, Larabee JL, Ballard JD. A sequence invariable region in TcdB2 is required for toxin escape from Clostridioides difficile. J Bacteriol 2024; 206:e0009624. [PMID: 38888328 PMCID: PMC11323933 DOI: 10.1128/jb.00096-24] [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: 03/06/2024] [Accepted: 05/23/2024] [Indexed: 06/20/2024] Open
Abstract
Sequence differences among the subtypes of Clostridioides difficile toxin TcdB (2,366 amino acids) are broadly distributed across the entire protein, with the notable exception of 76 residues at the protein's carboxy terminus. This sequence invariable region (SIR) is identical at the DNA and protein level among the TcdB variants, suggesting this string of amino acids has undergone selective pressure to prevent alterations. The functional role of the SIR domain in TcdB has not been determined. Analysis of a recombinantly constructed TcdB mutant lacking the SIR domain did not identify changes in TcdB's enzymatic or cytopathic activities. To further assess the SIR region, we constructed a C. difficile strain with the final 228 bp deleted from the tcdB gene, resulting in the production of a truncated form of TcdB lacking the SIR (TcdB2∆2291-2366). Using a combination of approaches, we found in the absence of the SIR sequence TcdB2∆2291-2366 retained cytotoxic activity but was not secreted from C. difficile. TcdB2∆2291-2366 was not released from the cell under autolytic conditions, indicating the SIR is involved in a more discrete step in toxin escape from the bacterium. Fractionation experiments combined with antibody detection found that TcdB2∆2291-2366 accumulates at the cell membrane but is unable to complete steps in secretion beyond this point. These data suggest conservation of the SIR domain across variants of TcdB could be influenced by the sequence's role in efficient escape of the toxin from C. difficile. IMPORTANCE Clostridioides difficile is a leading cause of antibiotic associated disease in the United States. The primary virulence factors produced by C. difficile are two large glucosylating toxins TcdA and TcdB. To date, several sequence variants of TcdB have been identified that differ in various functional properties. Here, we identified a highly conserved region among TcdB subtypes that is required for release of the toxin from C. difficile. This study reveals a putative role for the longest stretch of invariable sequence among TcdB subtypes and provides new details regarding toxin release into the extracellular environment. Improving our understanding of the functional roles of the conserved regions of TcdB variants aids in the development of new, broadly applicable strategies to treat CDI.
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Affiliation(s)
- Megan L. Kempher
- Department of
Microbiology and Immunology, University of Oklahoma Health Sciences
Center, Oklahoma City,
Oklahoma, USA
- Department of
Chemistry and Biochemistry, University of
Oklahoma, Norman,
Oklahoma, USA
| | - Tyler M. Shadid
- Department of
Microbiology and Immunology, University of Oklahoma Health Sciences
Center, Oklahoma City,
Oklahoma, USA
| | - Jason L. Larabee
- Department of
Microbiology and Immunology, University of Oklahoma Health Sciences
Center, Oklahoma City,
Oklahoma, USA
| | - Jimmy D. Ballard
- Department of
Microbiology and Immunology, University of Oklahoma Health Sciences
Center, Oklahoma City,
Oklahoma, USA
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Yang E, Cho YG, Kim E, Chang E, Bae S, Jung J, Kim MJ, Chong YP, Kim SH, Choi SH, Lee SO, Chung YS, Kim YS. Clinical and microbiological characteristics of persistent Staphylococcus aureus bacteremia, risk factors for mortality, and the role of CD4 + T cells. Sci Rep 2024; 14:15472. [PMID: 38969796 PMCID: PMC11226624 DOI: 10.1038/s41598-024-66520-0] [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: 01/24/2024] [Accepted: 07/02/2024] [Indexed: 07/07/2024] Open
Abstract
This study evaluated the determinants of mortality and the T cell immune response in patients with persistent Staphylococcus aureus bacteremia (SAB). This was a prospective cohort study and patients with confirmed SAB were enrolled from 2008 to 2020. We compared clinical, microbiological, and genotypic features between surviving and deceased patients with persistent SAB. The concentrations of cytokines and the proportions of IFN-γ secreting CD4+ T cells were measured serially during the bacteremia period. Of the 1760 patients, 242 had persistent bacteremia (PB), and 49 PB patients died within 30 days. In the multivariate analysis, the APACHE II score and female sex were independently associated with 30 days mortality. The level of IL-10 was significantly increased in the plasma of patients with a high Pitt bacteremia score and those who died within 12 weeks from the index day. The proportion of IFN-γ-secreting CD4+ T cells were the highest just before the positive-to-negative conversion of blood cultures in patients with a low Pitt bacteremia score and those who survived for 12 weeks. The level of IL-10 is correlated with clinical outcomes in PB patients. IFN-γ secreting CD4+ T cells might play a pivotal role in SAB PB.
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Affiliation(s)
- Eunmi Yang
- Division of Infectious Diseases, Seoul Medical Center, Seoul, South Korea
| | - Yeong Geon Cho
- Center for Antimicrobial Resistance and Microbial Genetics, University of Ulsan College of Medicine, Seoul, South Korea
- Asan Institute for Life Science, Asan Medical Center, Seoul, South Korea
| | - Eunsil Kim
- Center for Antimicrobial Resistance and Microbial Genetics, University of Ulsan College of Medicine, Seoul, South Korea
- Asan Institute for Life Science, Asan Medical Center, Seoul, South Korea
| | - Euijin Chang
- Division of Infectious Diseases, Asan Medical Center, University of Ulsan College of Medicine, 88, Olympic-ro43-gil, Songpa-gu, Seoul, 05505, South Korea
| | - Seongman Bae
- Center for Antimicrobial Resistance and Microbial Genetics, University of Ulsan College of Medicine, Seoul, South Korea
- Division of Infectious Diseases, Asan Medical Center, University of Ulsan College of Medicine, 88, Olympic-ro43-gil, Songpa-gu, Seoul, 05505, South Korea
| | - Jiwon Jung
- Division of Infectious Diseases, Asan Medical Center, University of Ulsan College of Medicine, 88, Olympic-ro43-gil, Songpa-gu, Seoul, 05505, South Korea
| | - Min Jae Kim
- Division of Infectious Diseases, Asan Medical Center, University of Ulsan College of Medicine, 88, Olympic-ro43-gil, Songpa-gu, Seoul, 05505, South Korea
| | - Yong Pil Chong
- Division of Infectious Diseases, Asan Medical Center, University of Ulsan College of Medicine, 88, Olympic-ro43-gil, Songpa-gu, Seoul, 05505, South Korea
| | - Sung-Han Kim
- Division of Infectious Diseases, Asan Medical Center, University of Ulsan College of Medicine, 88, Olympic-ro43-gil, Songpa-gu, Seoul, 05505, South Korea
| | - Sang-Ho Choi
- Division of Infectious Diseases, Asan Medical Center, University of Ulsan College of Medicine, 88, Olympic-ro43-gil, Songpa-gu, Seoul, 05505, South Korea
| | - Sang-Oh Lee
- Division of Infectious Diseases, Asan Medical Center, University of Ulsan College of Medicine, 88, Olympic-ro43-gil, Songpa-gu, Seoul, 05505, South Korea
| | - Yun Shin Chung
- Center for Antimicrobial Resistance and Microbial Genetics, University of Ulsan College of Medicine, Seoul, South Korea
| | - Yang Soo Kim
- Center for Antimicrobial Resistance and Microbial Genetics, University of Ulsan College of Medicine, Seoul, South Korea.
- Division of Infectious Diseases, Asan Medical Center, University of Ulsan College of Medicine, 88, Olympic-ro43-gil, Songpa-gu, Seoul, 05505, South Korea.
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3
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Luo ZX, Li Y, Liu MF, Zhao R. Ciprofloxacin enhances the biofilm formation of Staphylococcus aureus via an agrC-dependent mechanism. Front Microbiol 2023; 14:1328947. [PMID: 38179460 PMCID: PMC10764545 DOI: 10.3389/fmicb.2023.1328947] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2023] [Accepted: 12/04/2023] [Indexed: 01/06/2024] Open
Abstract
Staphylococcus aureus readily forms biofilms on host tissues and medical devices, enabling its persistence in chronic infections and resistance to antibiotic therapy. The accessory gene regulator (Agr) quorum sensing system plays a key role in regulating S. aureus biofilm formation. This study reveals the widely used fluoroquinolone antibiotic, ciprofloxacin, strongly stimulates biofilm formation in methicillin-resistant S. aureus, methicillin-sensitive S. aureus, and clinical isolates with diverse genetic backgrounds. Crystal violet staining indicated that ciprofloxacin induced a remarkable 12.46- to 15.19-fold increase in biofilm biomass. Confocal laser scanning microscopy revealed that ciprofloxacin induced denser biofilms. Phenotypic assays suggest that ciprofloxacin may enhance polysaccharide intercellular adhesin production, inhibit autolysis, and reduce proteolysis during the biofilm development, thus promoting initial adhesion and enhancing biofilm stability. Mechanistically, ciprofloxacin significantly alters the expression of various biofilm-related genes (icaA, icaD, fnbA, fnbB, eap, emp) and regulators (agrA, saeR). Gene knockout experiments revealed that deletion of agrC, rather than saeRS, abolishes the ciprofloxacin-induced enhancement of biofilm formation, underscoring the key role of agrC. Thermal shift assays showed ciprofloxacin binds purified AgrC protein, thereby inhibiting the Agr system. Molecular docking results further support the potential interaction between ciprofloxacin and AgrC. In summary, subinhibitory concentrations of ciprofloxacin stimulate S. aureus biofilm formation via an agrC-dependent pathway. This inductive effect may facilitate local infection establishment and bacterial persistence, ultimately leading to therapeutic failure.
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Affiliation(s)
- Zhao-xia Luo
- Department of Clinical Laboratory, Medical Center of Burn Plastic and Wound Repair, The First Affiliated Hospital of Nanchang University, Nanchang, China
- School of Public Health, Nanchang University, Nanchang, China
| | - Yuting Li
- Department of Clinical Laboratory, Medical Center of Burn Plastic and Wound Repair, The First Affiliated Hospital of Nanchang University, Nanchang, China
- School of Public Health, Nanchang University, Nanchang, China
| | - Mei-fang Liu
- Department of Clinical Laboratory, Medical Center of Burn Plastic and Wound Repair, The First Affiliated Hospital of Nanchang University, Nanchang, China
| | - Rui Zhao
- Department of Clinical Laboratory, Medical Center of Burn Plastic and Wound Repair, The First Affiliated Hospital of Nanchang University, Nanchang, China
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Clark AE, Adamson CC, Carothers KE, Roxas BAP, Viswanathan VK, Vedantam G. The Alternative Sigma Factor SigL Influences Clostridioides difficile Toxin Production, Sporulation, and Cell Surface Properties. Front Microbiol 2022; 13:871152. [PMID: 35633701 PMCID: PMC9130780 DOI: 10.3389/fmicb.2022.871152] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2022] [Accepted: 04/06/2022] [Indexed: 12/18/2022] Open
Abstract
The alternative sigma factor SigL (Sigma-54) facilitates bacterial adaptation to the extracellular environment by modulating the expression of defined gene subsets. A homolog of the gene encoding SigL is conserved in the diarrheagenic pathogen Clostridioides difficile. To explore the contribution of SigL to C. difficile biology, we generated sigL-disruption mutants (sigL::erm) in strains belonging to two phylogenetically distinct lineages-the human-relevant Ribotype 027 (strain BI-1) and the veterinary-relevant Ribotype 078 (strain CDC1). Comparative proteomics analyses of mutants and isogenic parental strains revealed lineage-specific SigL regulons. Concomitantly, loss of SigL resulted in pleiotropic and distinct phenotypic alterations in the two strains. Sporulation kinetics, biofilm formation, and cell surface-associated phenotypes were altered in CDC1 sigL::erm relative to the isogenic parent strain but remained unchanged in BI-1 sigL::erm. In contrast, secreted toxin levels were significantly elevated only in the BI-1 sigL::erm mutant relative to its isogenic parent. We also engineered SigL overexpressing strains and observed enhanced biofilm formation in the CDC1 background, and reduced spore titers as well as dampened sporulation kinetics in both strains. Thus, we contend that SigL is a key, pleiotropic regulator that dynamically influences C. difficile's virulence factor landscape, and thereby, its interactions with host tissues and co-resident microbes.
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Affiliation(s)
- Andrew E. Clark
- School of Animal and Comparative Biomedical Sciences, Tucson, AZ, United States
| | - Chelsea C. Adamson
- School of Animal and Comparative Biomedical Sciences, Tucson, AZ, United States
| | | | | | - V. K. Viswanathan
- School of Animal and Comparative Biomedical Sciences, Tucson, AZ, United States
- Department of Immunobiology, University of Arizona, Tucson, AZ, United States
- BIO5 Institute for Collaborative Research, University of Arizona, Tucson, AZ, United States
| | - Gayatri Vedantam
- School of Animal and Comparative Biomedical Sciences, Tucson, AZ, United States
- Department of Immunobiology, University of Arizona, Tucson, AZ, United States
- BIO5 Institute for Collaborative Research, University of Arizona, Tucson, AZ, United States
- Southern Arizona VA Healthcare System, Tucson, AZ, United States
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5
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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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Impact of agr Functionality on the Outcome of Patients with Methicillin-Susceptible Staphylococcus aureus Bacteremia. Microbiol Spectr 2021; 9:e0011621. [PMID: 34378959 PMCID: PMC8552762 DOI: 10.1128/spectrum.00116-21] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Dysfunctional accessory gene regulator (agr) is associated with unfavorable outcomes in invasive methicillin-resistant Staphylococcus aureus infections. However, it is unknown whether this association persists in methicillin-susceptible Staphylococcus aureus bacteremia (MSSA-B). This study evaluated the association between agr dysfunction and mortality in patients with MSSA-B. This retrospective cohort study included MSSA-B patients (≥15 years) enrolled from June 2014 to June 2019 and retrospectively collected their demographic and clinical information. Stored causative strains were measured for agr functionality by δ-hemolysin production assays. Among 244 MSSA-B patients, 91 (37.3%) and 153 (62.7%) had dysfunctional and functional agr MSSA-B, respectively. Ninety-day mortality occurred in 18.7% and 17.6% dysfunctional and functional groups, respectively (P = 0.97). Kaplan-Meier analysis showed that mortality due to dysfunctional agr MSSA-B was not significantly higher (P = 0.82). Age, sites, the severity of infection, and comorbidity adjusted hazard ratio (aHR) of the dysfunctional group for 90-day mortality was 1.303 (95% confidence interval [CI], 0.698 to 2.436, P = 0.41). Mortality due to MSSA-B with sequential organ failure assessment (SOFA) scores of 2 to 5 was significantly higher in the dysfunctional group (P = 0.03), and the dysfunctional agr aHR for 90-day mortality was 3.260 (95% CI, 1.050 to 10.118, P = 0.04). The agr dysfunction of causative organisms can have a significant effect on the outcomes of MSSA-B in patients with moderate severity (SOFA scores 2 to 5). IMPORTANCE Few studies have examined the association between methicillin-susceptible Staphylococcus aureus (MSSA) infection and accessory gene regulator (agr) functionality. We evaluated the association between agr dysfunction and mortality in patients with MSSA bacteremia. Dysfunctional agr is associated with lower survival in MSSA bacteremia patients with moderately severe sequential organ failure assessment (SOFA) scores of 2 to 5. We found that the agr functionality of causative organisms may have an effect on patients’ outcomes in MSSA like in methicillin-resistant S. aureus.
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7
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Dotto C, Lombarte Serrat A, Ledesma M, Vay C, Ehling-Schulz M, Sordelli DO, Grunert T, Buzzola F. Salicylic acid stabilizes Staphylococcus aureus biofilm by impairing the agr quorum-sensing system. Sci Rep 2021; 11:2953. [PMID: 33536503 PMCID: PMC7858585 DOI: 10.1038/s41598-021-82308-y] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2020] [Accepted: 01/19/2021] [Indexed: 01/30/2023] Open
Abstract
Salicylic acid (SAL) has recently been shown to induce biofilm formation in Staphylococcus aureus and to affect the expression of virulence factors. This study was aimed to investigate the effect of SAL on the regulatory agr system and its impact on S. aureus biofilm formation. The agr quorum-sensing system, which is a central regulator in S. aureus pathogenicity, plays a pivotal role in the dispersal of S. aureus mature biofilms and contributes to the creation of new colonization sites. Here, we demonstrate that SAL impairs biofilm dispersal by interfering with agr expression. As revealed by our work, protease and surfactant molecule production is diminished, and bacterial cell autolysis is also negatively affected by SAL. Furthermore, as a consequence of SAL treatment, the S. aureus biofilm matrix revealed the lack of extracellular DNA. In silico docking and simulation of molecular dynamics provided evidence for a potential interaction of AgrA and SAL, resulting in reduced activity of the agr system. In conclusion, SAL stabilized the mature S. aureus biofilms, which may prevent bacterial cell dissemination. However, it may foster the establishment of infections locally and consequently increase bacterial persistence leading to therapeutic failure.
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Affiliation(s)
- Cristian Dotto
- Instituto de Investigaciones en Microbiología y Parasitología Médica (IMPaM), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Universidad de Buenos Aires, Buenos Aires, Argentina
- Departamento de Microbiología, Parasitología e Inmunología, Facultad de Medicina, Universidad de Buenos Aires, Buenos Aires, Argentina
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres" (INGEBI), CONICET, Buenos Aires, Argentina
| | - Andrea Lombarte Serrat
- Instituto de Investigaciones en Microbiología y Parasitología Médica (IMPaM), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Universidad de Buenos Aires, Buenos Aires, Argentina
- Departamento de Microbiología, Parasitología e Inmunología, Facultad de Medicina, Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Martín Ledesma
- Instituto de Fisiopatología y Bioquímica Clínica (INFIBIOC), Facultad de Farmacia y Bioquímica, Hospital de Clínicas José de San Martín, Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Carlos Vay
- Instituto de Fisiopatología y Bioquímica Clínica (INFIBIOC), Facultad de Farmacia y Bioquímica, Hospital de Clínicas José de San Martín, Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Monika Ehling-Schulz
- Functional Microbiology, Institute of Microbiology, Department of Pathobiology, University of Veterinary Medicine, Vienna, Austria
| | - Daniel O Sordelli
- Instituto de Investigaciones en Microbiología y Parasitología Médica (IMPaM), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Universidad de Buenos Aires, Buenos Aires, Argentina
- Departamento de Microbiología, Parasitología e Inmunología, Facultad de Medicina, Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Tom Grunert
- Functional Microbiology, Institute of Microbiology, Department of Pathobiology, University of Veterinary Medicine, Vienna, Austria
| | - Fernanda Buzzola
- Instituto de Investigaciones en Microbiología y Parasitología Médica (IMPaM), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Universidad de Buenos Aires, Buenos Aires, Argentina.
- Departamento de Microbiología, Parasitología e Inmunología, Facultad de Medicina, Universidad de Buenos Aires, Buenos Aires, Argentina.
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Lee SO, Lee S, Lee JE, Song KH, Kang CK, Wi YM, San-Juan R, López-Cortés LE, Lacoma A, Prat C, Jang HC, Kim ES, Kim HB, Lee SH. Dysfunctional accessory gene regulator (agr) as a prognostic factor in invasive Staphylococcus aureus infection: a systematic review and meta-analysis. Sci Rep 2020; 10:20697. [PMID: 33244173 PMCID: PMC7691521 DOI: 10.1038/s41598-020-77729-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2020] [Accepted: 11/17/2020] [Indexed: 12/14/2022] Open
Abstract
The accessory gene regulator (agr) locus of Staphylococcus aureus is a quorum-sensing virulence regulator. Although there are many studies concerning the effect of dysfunctional agr on the outcomes of S. aureus infection, there is no systematic review to date. We systematically searched for clinical studies reporting outcomes of invasive S. aureus infections and the proportion of dysfunctional agr among their causative strains, and we performed a meta-analysis to obtain estimates of the odds of outcomes of invasive S. aureus infection with dysfunctional versus functional agr. Of 289 articles identified by our research strategy, 20 studies were meta-analysed for crude analysis of the impact of dysfunctional agr on outcomes of invasive S. aureus infection. Dysfunctional agr was generally associated with unfavourable outcomes (OR 1.32, 95% CI 1.05–1.66), and the impact of dysfunctional agr on outcome was more prominent in invasive methicillin-resistant S. aureus (MRSA) infections (OR 1.54, CI 1.20–1.97). Nine studies were meta-analysed for the impact of dysfunctional agr on the 30-day mortality of invasive S. aureus infection. Invasive MRSA infection with dysfunctional agr exhibited higher 30-day mortality (OR 1.40, CI 1.03–1.90) than that with functional agr. On the other hand, invasive MSSA infection with dysfunctional agr exhibited lower 30-day mortality (OR 0.51, CI 0.27–0.95). In the post hoc subgroup analysis by the site of MRSA infection, dysfunctional agr was associated with higher 30-day mortality in MRSA pneumonia (OR 2.48, CI 1.17–5.25). The effect of dysfunctional agr on the outcome of invasive S. aureus infection may vary depending on various conditions, such as oxacillin susceptibility and the site of infection. Dysfunctional agr was generally associated with unfavourable clinical outcomes and its effect was prominent in MRSA and pneumonia. Dysfunctional agr may be applicable for outcome prediction in cases of invasive MRSA infection with hardly eradicable foci such as pneumonia.
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Affiliation(s)
- Soon Ok Lee
- Department of Internal Medicine, Pusan National University School of Medicine and Medical Research Institute, Pusan National University Hospital, 179 Gudeok-ro, Seo-gu, Busan, 49241, Republic of Korea
| | - Shinwon Lee
- Department of Internal Medicine, Pusan National University School of Medicine and Medical Research Institute, Pusan National University Hospital, 179 Gudeok-ro, Seo-gu, Busan, 49241, Republic of Korea.
| | - Jeong Eun Lee
- Department of Internal Medicine, Pusan National University School of Medicine and Medical Research Institute, Pusan National University Hospital, 179 Gudeok-ro, Seo-gu, Busan, 49241, Republic of Korea
| | - Kyoung-Ho Song
- Department of Internal Medicine, Seoul National University College of Medicine and Seoul National University Bundang Hospital, Seongnam, Republic of Korea
| | - Chang Kyung Kang
- Department of Internal Medicine, Seoul National University College of Medicine and Seoul National University Hospital, Seoul, Republic of Korea
| | - Yu Mi Wi
- Division of Infectious Diseases, Samsung Changwon Hospital, Sungkyunkwan University School of Medicine, Changwon, Republic of Korea
| | - Rafael San-Juan
- Unit of Infectious Diseases, University Hospital 12 de Octubre, Instituto de Investigación Hospital "12 de Octubre" (i+12), Universidad Complutense, Avenida de Córdoba, s/n, Madrid, Spain
| | - Luis E López-Cortés
- Unidad Clínica de Enfermedades Infecciosas, Microbiología y Medicina Preventiva, Hospital Universitario Virgen Macarena/Departamento de Medicina, Universidad de Sevilla/Instituto de Biomedicina de Sevilla, Sevilla, Spain
| | - Alicia Lacoma
- Microbiology Department, Hospital Universitari Germans Trias i Pujol, Institut d' Investigació Germans Trias i Pujol, CIBER Enfermedades Respiratorias (CIBERES), Universitat Autònoma de Barcelona, Badalona, Spain
| | - Cristina Prat
- Microbiology Department, Hospital Universitari Germans Trias i Pujol, Institut d' Investigació Germans Trias i Pujol, CIBER Enfermedades Respiratorias (CIBERES), Universitat Autònoma de Barcelona, Badalona, Spain.,Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht, Utrecht University, Utrecht, The Netherlands
| | - Hee-Chang Jang
- Department of Infectious Diseases, Chonnam National University Medical School, Gwang-ju, Republic of Korea
| | - Eu Suk Kim
- Department of Internal Medicine, Seoul National University College of Medicine and Seoul National University Bundang Hospital, Seongnam, Republic of Korea
| | - Hong Bin Kim
- Department of Internal Medicine, Seoul National University College of Medicine and Seoul National University Bundang Hospital, Seongnam, Republic of Korea
| | - Sun Hee Lee
- Department of Internal Medicine, Pusan National University School of Medicine and Medical Research Institute, Pusan National University Hospital, 179 Gudeok-ro, Seo-gu, Busan, 49241, Republic of Korea
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9
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Yee R, Feng J, Wang J, Chen J, Zhang Y. Identification of Genes Regulating Cell Death in Staphylococcus aureus. Front Microbiol 2019; 10:2199. [PMID: 31632363 PMCID: PMC6779855 DOI: 10.3389/fmicb.2019.02199] [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: 06/25/2019] [Accepted: 09/09/2019] [Indexed: 12/20/2022] Open
Abstract
Staphylococcus aureus is an opportunistic pathogen that causes acute and chronic infections. Due to S. aureus's highly resistant and persistent nature, it is paramount to identify better drug targets in order to eradicate S. aureus infections. Despite the efforts in understanding bacterial cell death, the genes, and pathways of S. aureus cell death remain elusive. Here, we performed a genome-wide screen using a transposon mutant library to study the genetic mechanisms involved in S. aureus cell death. Using a precisely controlled heat-ramp and acetic acid exposure assays, mutations in 27 core genes (hsdR1, hslO, nsaS, sspA, folD, mfd, vraF, kdpB, USA300HOU_2684, 0868, 0369, 0420, 1154, 0142, 0930, 2590, 0997, 2559, 0044, 2004, 1209, 0152, 2455, 0154, 2386, 0232, 0350 involved in transporters, transcription, metabolism, peptidases, kinases, transferases, SOS response, nucleic acid, and protein synthesis) caused the bacteria to be more death-resistant. In addition, we identified mutations in 10 core genes (capA, gltT, mnhG1, USA300HOU_1780, 2496, 0200, 2029, 0336, 0329, 2386, involved in transporters, metabolism, transcription, and cell wall synthesis) from heat-ramp and acetic acid that caused the bacteria to be more death-sensitive or with defect in persistence. Interestingly, death-resistant mutants were more virulent than the parental strain USA300 and caused increased mortality in a Caenorhabditis elegans infection model. Conversely, death-sensitive mutants were less persistent and formed fewer persister cells upon exposure to different classes of antibiotics. These findings provide new insights into the mechanisms of S. aureus cell death and offer new therapeutic targets for developing more effective treatments for infections caused by S. aureus.
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Affiliation(s)
- Rebecca Yee
- Department of Molecular Microbiology and Immunology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD, United States
| | - Jie Feng
- Department of Molecular Microbiology and Immunology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD, United States
| | - Jiou Wang
- Department of Biochemistry and Molecular Biology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD, United States
| | - Jiazhen Chen
- Department of Infectious Diseases, Huashan Hospital, Fudan University, Shanghai, China
| | - Ying Zhang
- Department of Molecular Microbiology and Immunology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD, United States
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The agr quorum sensing system in Staphylococcus aureus cells mediates death of sub-population. BMC Res Notes 2018; 11:503. [PMID: 30041686 PMCID: PMC6057012 DOI: 10.1186/s13104-018-3600-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2018] [Accepted: 07/12/2018] [Indexed: 01/22/2023] Open
Abstract
Objective In the human pathogen, Staphylococcus aureus, the agr quorum sensing system controls expression of a multitude of virulence factors and yet, agr negative cells frequently arise both in the laboratory and in some infections. The aim of this study was to examine the possible reasons behind this phenomenon. Results We examined viability of wild type and agr mutant cell cultures using a live-dead stain and observed that in stationary phase, 3% of the wild type population became non-viable whereas for agr mutant cells non-viable cells were barely detectable. The effect appears to be mediated by RNAIII, the effector molecule of agr, as ectopic overexpression of RNAIII resulted in 60% of the population becoming non-viable. This effect was not due to toxicity from delta toxin that is encoded by the hld gene located within RNAIII as hld overexpression did not cause cell death. Importantly, lysed S. aureus cells promoted bacterial growth. Our data suggest that RNAIII mediated cell death of agr positive but not agr negative cells provides a selective advantage to the agr negative cell population and may contribute to the common appearance of agr negative cells in S. aureus populations. Electronic supplementary material The online version of this article (10.1186/s13104-018-3600-6) contains supplementary material, which is available to authorized users.
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11
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Exposure of Staphylococcus aureus to Targocil Blocks Translocation of the Major Autolysin Atl across the Membrane, Resulting in a Significant Decrease in Autolysis. Antimicrob Agents Chemother 2018; 62:AAC.00323-18. [PMID: 29735561 DOI: 10.1128/aac.00323-18] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2018] [Accepted: 04/29/2018] [Indexed: 11/20/2022] Open
Abstract
Peptidoglycan (PG) and wall teichoic acid (WTA) are the major staphylococcal cell wall components, and WTA biosynthesis has recently been explored for drug development. Targocil is a novel agent that targets the TarG subunit of the WTA translocase (TarGH) that transports WTA across the membrane to the wall. Previously we showed that targocil treatment of a methicillin-susceptible Staphylococcus aureus strain led to a rapid shut down of cellular autolysis. Targocil II, which targets the TarH subunit of TarGH, also resulted in a drastic decrease in autolysis. Here, we address the mechanism of targocil-mediated decreased autolysis. The mechanism is WTA dependent since targocil treatment decreased autolysis in methicillin-resistant strains but not in a WTA-deficient mutant. Similar to cellular autolysis, autolysin-retaining crude cell walls isolated from targocil-treated cells had vastly decreased autolytic activity compared to those from untreated cells. Purified cell walls from control and targocil-treated cells, which lack autolytic activity, were similarly susceptible to lysozyme and lysostaphin and had similar O-acetyl contents, indicating that targocil treatment did not grossly alter PG structure and chemistry. Purified cell walls from targocil-treated cells were highly susceptible to autolysin extracts, supporting the notion that targocil treatment led to decreased autolysin in the crude cell walls. Quantitative real-time PCR analysis revealed that the decrease in autolysis in the targocil-exposed cells was not due to transcriptional repression of the autolysin genes atl, lytM, lytN, and sle1 Zymographic analysis of peptidoglycan hydrolase profiles showed a deficiency of cell surface autolysins in targocil-treated cells but higher activity in cell membrane fractions. Here, we propose that the untranslocated WTA molecules in the targocil-exposed cells sequester Atl at the membrane, resulting in significantly decreased autolysis.
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Bojer MS, Lindemose S, Vestergaard M, Ingmer H. Quorum Sensing-Regulated Phenol-Soluble Modulins Limit Persister Cell Populations in Staphylococcus aureus. Front Microbiol 2018; 9:255. [PMID: 29515541 PMCID: PMC5826201 DOI: 10.3389/fmicb.2018.00255] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2017] [Accepted: 01/31/2018] [Indexed: 11/15/2022] Open
Abstract
Incomplete killing of bacterial pathogens by antibiotics is an underlying cause of treatment failure and accompanying complications. Among those avoiding chemotherapy are persisters being individual cells in a population that for extended periods of time survive high antibiotic concentrations proposedly by being in a quiescent state refractory to antibiotic killing. While investigating the human pathogen Staphylococcus aureus and the influence of growth phase on persister formation, we noted that spent supernatants of stationary phase cultures of S. aureus or S. epidermidis, but not of distantly related bacteria, significantly reduced the persister cell frequency upon ciprofloxacin challenge when added to exponentially growing and stationary phase S. aureus cells. Curiously, the persister reducing activity of S. aureus supernatants was also effective against persisters formed by either S. carnosus or Listeria monocytogenes. The persister reducing component, which resisted heat but not proteases and was produced in the late growth phase in an agr quorum-sensing dependent manner, was identified to be the phenol-soluble modulin (PSM) toxins. S. aureus express several PSMs, each with distinct cytolytic and antimicrobial properties; however, the persister reducing activity was specifically linked to synthesis of the PSMα family. Correspondingly, a high-persister phenotype of a PSMα mutant was observed upon fluoroquinolone or aminoglycoside challenge, demonstrating that the persister reducing activity of PSMs can be endogenously synthesized or extrinsically added. Given that PSMs have been associated with lytic activity against bacterial membranes we propose that PSM toxins increase the susceptibility of persister cells to killing by intracellularly acting antibiotics and that chronic and re-occurring infections with quorum sensing, agr negative mutants may be difficult to treat with antibiotics because of persister cells formed in the absence of PSM toxins.
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Affiliation(s)
- Martin S. Bojer
- Faculty of Health and Medical Sciences, Department of Veterinary and Animal Sciences, University of Copenhagen, Copenhagen, Denmark
- Centre for Bacterial Stress Response and Persistence, University of Copenhagen, Copenhagen, Denmark
| | - Søren Lindemose
- Centre for Bacterial Stress Response and Persistence, University of Copenhagen, Copenhagen, Denmark
| | - Martin Vestergaard
- Faculty of Health and Medical Sciences, Department of Veterinary and Animal Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Hanne Ingmer
- Faculty of Health and Medical Sciences, Department of Veterinary and Animal Sciences, University of Copenhagen, Copenhagen, Denmark
- Centre for Bacterial Stress Response and Persistence, University of Copenhagen, Copenhagen, Denmark
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Abstract
Staphylococcus aureus is often involved in severe infections, in which the effects of bacterial virulence factors have great importance. Antistaphylococcal regimens should take into account the different effects of antibacterial agents on the expression of virulence factors and on the host's immune response. A PubMed literature search was performed to select relevant articles on the effects of antibiotics on staphylococcal toxin production and on the host immune response. Information was sorted according to the methods used for data acquisition (bacterial strains, growth models, and antibiotic concentrations) and the assays used for readout generation. The reported mechanisms underlying S. aureus virulence modulation by antibiotics were reviewed. The relevance of in vitro observations is discussed in relation to animal model data and to clinical evidence extracted from case reports and recommendations on the management of toxin-related staphylococcal diseases. Most in vitro data point to a decreased level of virulence expression upon treatment with ribosomally active antibiotics (linezolid and clindamycin), while cell wall-active antibiotics (beta-lactams) mainly increase exotoxin production. In vivo studies confirmed the suppressive effect of clindamycin and linezolid on virulence expression, supporting their utilization as a valuable management strategy to improve patient outcomes in cases of toxin-associated staphylococcal disease.
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Zheng W, Cai X, Xie M, Liang Y, Wang T, Li Z. Structure-Based Identification of a Potent Inhibitor Targeting Stp1-Mediated Virulence Regulation in Staphylococcus aureus. Cell Chem Biol 2016; 23:1002-13. [PMID: 27499528 DOI: 10.1016/j.chembiol.2016.06.014] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2016] [Revised: 06/15/2016] [Accepted: 06/17/2016] [Indexed: 11/26/2022]
Abstract
The increasing threats of antibiotic resistance urge the need for developing new strategies against bacterial infections. Targeting eukaryotic-like Ser/Thr phosphatase Stp1-mediated virulence regulation represents a promising approach for combating staphylococcal infection yet to be explored. Here, we report the 2.32-Å resolution crystal structure of Stp1. Stp1 binds an unexpected fourth metal ion, which is important for Stp1's enzymatic activity as demonstrated by amino acid substitution studies. Inspired by the structural details of Stp1, we identified a potent and selective Stp1 inhibitor, aurintricarboxylic acid (ATA). Transcriptome analysis and biochemical studies supported Stp1 as the target of ATA inhibition within the pathogen, preventing upregulation of virulence genes. Notably, ATA did not affect in vitro growth of Staphylococcus aureus, while simultaneously attenuating staphylococcal virulence in mice. Our findings demonstrate that ATA is a potent anti-virulence compound against staphylococcal infection, laying the foundation for further developing new scaffolds for Stp1-targeted small molecules.
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Affiliation(s)
- Weihao Zheng
- Key Lab of Chemical Genomics, School of Chemical Biology and Biotechnology, Shenzhen Graduate School, Peking University, Shenzhen 518055, China
| | - Xiaodan Cai
- Key Lab of Chemical Genomics, School of Chemical Biology and Biotechnology, Shenzhen Graduate School, Peking University, Shenzhen 518055, China
| | - Mingsheng Xie
- Key Lab of Chemical Genomics, School of Chemical Biology and Biotechnology, Shenzhen Graduate School, Peking University, Shenzhen 518055, China
| | - Yujie Liang
- Key Lab of Chemical Genomics, School of Chemical Biology and Biotechnology, Shenzhen Graduate School, Peking University, Shenzhen 518055, China
| | - Tao Wang
- Department of Biology, South University of Science and Technology of China, Shenzhen 518055, China; SZCDC-SUSTech Joint Key Laboratory for Tropical Diseases, Shenzhen Center for Disease Control and Prevention, Shenzhen, 518055, China.
| | - Zigang Li
- Key Lab of Chemical Genomics, School of Chemical Biology and Biotechnology, Shenzhen Graduate School, Peking University, Shenzhen 518055, China.
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15
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Mandal S, Mahapa A, Biswas A, Jana B, Polley S, Sau K, Sau S. A Surfactant-Induced Functional Modulation of a Global Virulence Regulator from Staphylococcus aureus. PLoS One 2016; 11:e0151426. [PMID: 26989900 PMCID: PMC4798592 DOI: 10.1371/journal.pone.0151426] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2016] [Accepted: 02/29/2016] [Indexed: 11/24/2022] Open
Abstract
Triton X-100 (TX-100), a useful non-ionic surfactant, reduced the methicillin resistance in Staphylococcus aureus significantly. Many S. aureus proteins were expressed in the presence of TX-100. SarA, one of the TX-100-induced proteins, acts as a global virulence regulator in S. aureus. To understand the effects of TX-100 on the structure, and function of SarA, a recombinant S. aureus SarA (rSarA) and its derivative (C9W) have been investigated in the presence of varying concentrations of this surfactant using various probes. Our data have revealed that both rSarA and C9W bind to the cognate DNA with nearly similar affinity in the absence of TX-100. Interestingly, their DNA binding activities have been significantly increased in the presence of pre-micellar concentration of TX-100. The increase of TX-100 concentrations to micellar or post-micellar concentration did not greatly enhance their activities further. TX-100 molecules have altered the secondary and tertiary structures of both proteins to some extents. Size of the rSarA-TX-100 complex appears to be intermediate to those of rSarA and TX-100. Additional analyses show a relatively moderate interaction between C9W and TX-100. Binding of TX-100 to C9W has, however, occurred by a cooperative pathway particularly at micellar and higher concentrations of this surfactant. Taken together, TX-100-induced structural alteration of rSarA and C9W might be responsible for their increased DNA binding activity. As TX-100 has stabilized the somewhat weaker SarA-DNA complex effectively, it could be used to study its structure in the future.
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Affiliation(s)
- Sukhendu Mandal
- Department of Biochemistry, Bose Institute, Kolkata, West Bengal, India
| | - Avisek Mahapa
- Department of Biotechnology, Haldia Institute of Technology, Haldia, West Bengal, India
| | - Anindya Biswas
- Department of Biochemistry, Bose Institute, Kolkata, West Bengal, India
| | - Biswanath Jana
- Department of Biochemistry, Bose Institute, Kolkata, West Bengal, India
| | - Soumitra Polley
- Department of Biochemistry, Bose Institute, Kolkata, West Bengal, India
| | - Keya Sau
- Department of Biotechnology, Haldia Institute of Technology, Haldia, West Bengal, India
- * E-mail: (KS); (SS)
| | - Subrata Sau
- Department of Biochemistry, Bose Institute, Kolkata, West Bengal, India
- * E-mail: (KS); (SS)
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16
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Lioliou E, Fechter P, Caldelari I, Jester BC, Dubrac S, Helfer AC, Boisset S, Vandenesch F, Romby P, Geissmann T. Various checkpoints prevent the synthesis of Staphylococcus aureus peptidoglycan hydrolase LytM in the stationary growth phase. RNA Biol 2016; 13:427-40. [PMID: 26901414 DOI: 10.1080/15476286.2016.1153209] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
In Staphylococcus aureus, peptidoglycan metabolism plays a role in the host inflammatory response and pathogenesis. Transcription of the peptidoglycan hydrolases is activated by the essential 2-component system WalKR at low cell density. During stationary growth phase, WalKR is not active and transcription of the peptidoglycan hydrolase genes is repressed. In this work, we studied regulation of expression of the glycylglycine endopeptidase LytM. We show that, in addition to the transcriptional regulation mediated by WalKR, the synthesis of LytM is negatively controlled by a unique mechanism at the stationary growth phase. We have identified 2 different mRNAs encoding lytM, which vary in the length of their 5' untranslated (5'UTR) regions. LytM is predominantly produced from the WalKR-regulated mRNA transcript carrying a short 5'UTR. The lytM mRNA is also transcribed as part of a polycistronic operon with the upstream SA0264 gene and is constitutively expressed. Although SA0264 protein can be synthesized from the longer operon transcript, lytM cannot be translated because its ribosome-binding site is sequestered into a translationally inactive secondary structure. In addition, the effector of the agr system, RNAIII, can inhibit translation of lytM present on the operon without altering the transcript level but does not have an effect on the translation of the upstream gene. We propose that this dual regulation of lytM expression, at the transcriptional and post-transcriptional levels, contributes to prevent cell wall damage during the stationary phase of growth.
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Affiliation(s)
- Efthimia Lioliou
- a Architecture et Réactivité de l'ARN, Université de Strasbourg, CNRS, IBMC , 15 rue René Descartes, Strasbourg , France
| | - Pierre Fechter
- a Architecture et Réactivité de l'ARN, Université de Strasbourg, CNRS, IBMC , 15 rue René Descartes, Strasbourg , France
| | - Isabelle Caldelari
- a Architecture et Réactivité de l'ARN, Université de Strasbourg, CNRS, IBMC , 15 rue René Descartes, Strasbourg , France
| | - Brian C Jester
- b Institute of Systems and Synthetic Biology, University of Evry-Val-d'Essonne, CNRS FRE3561 , Evry , France
| | - Sarah Dubrac
- c Unité de Biologie des Bactéries pathogènes à Gram-positif, Institut Pasteur , 28 rue du Dr Roux, Paris , France
| | - Anne-Catherine Helfer
- a Architecture et Réactivité de l'ARN, Université de Strasbourg, CNRS, IBMC , 15 rue René Descartes, Strasbourg , France
| | - Sandrine Boisset
- d CIRI, Center International de Recherche en Infectiologie - Inserm U1111 - Université Lyon 1 - Ecole Normale Supérieure de Lyon - CNRS UMR5308 , 21 Avenue Tony Garnier, LYON cedex 07 , France
| | - François Vandenesch
- d CIRI, Center International de Recherche en Infectiologie - Inserm U1111 - Université Lyon 1 - Ecole Normale Supérieure de Lyon - CNRS UMR5308 , 21 Avenue Tony Garnier, LYON cedex 07 , France
| | - Pascale Romby
- a Architecture et Réactivité de l'ARN, Université de Strasbourg, CNRS, IBMC , 15 rue René Descartes, Strasbourg , France
| | - Thomas Geissmann
- d CIRI, Center International de Recherche en Infectiologie - Inserm U1111 - Université Lyon 1 - Ecole Normale Supérieure de Lyon - CNRS UMR5308 , 21 Avenue Tony Garnier, LYON cedex 07 , France
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17
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Loss of Antibiotic Tolerance in Sod-Deficient Mutants Is Dependent on the Energy Source and Arginine Catabolism in Enterococci. J Bacteriol 2015; 197:3283-93. [PMID: 26260456 DOI: 10.1128/jb.00389-15] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2015] [Accepted: 07/31/2015] [Indexed: 01/25/2023] Open
Abstract
UNLABELLED Enterococci are naturally tolerant to typically bactericidal cell wall-active antibiotics, meaning that their growth is inhibited but they are not killed even when exposed to a high concentration of the drug. The molecular reasons for this extraordinary tolerance are still incompletely understood. Previous work showed that resistance to killing collapsed specifically in mutants affected in superoxide dismutase (Sod) activity, arguing that bactericidal antibiotic treatment led to induction of a superoxide burst. In the present work, we show that loss of antibiotic tolerance in ΔsodA mutants of pathogenic enterococci is dependent on the energy source present during antibiotic treatment. Hexoses induce greater killing than the pentose ribose, and no killing was observed with glycerol as the energy source. These results point to glycolytic reactions as crucial for antibiotic-mediated killing of ΔsodA mutants. A transposon mutant library was constructed in Enterococcus faecalis ΔsodA mutants and screened for restored tolerance of vancomycin. Partially restored tolerance was observed in mutants with transposon integrations into intergenic regions upstream of regulators implicated in arginine catabolism. In these mutants, the arginine deiminase operon was highly upregulated. A model for the action of cell wall-active antibiotics in tolerant and nontolerant bacteria is proposed. IMPORTANCE Antibiotic tolerance is a serious clinical concern, since tolerant bacteria have considerably increased abilities to resist killing by bactericidal drugs. Using enterococci as models for highly antibiotic-tolerant pathogens, we showed that tolerance of these bacteria is linked to their superoxide dismutase (Sod), arguing that bactericidal antibiotics induce generation of reactive oxygen species inside cells. Wild-type strains are tolerant because they detoxify these deleterious molecules by the activity of Sod, whereas Sod-deficient strains are killed. This study showed that killing depends on the energy source present during treatment and that an increase in arginine catabolism partially restored tolerance of the Sod mutants. These results are used to propose a mode-of-action model of cell wall-active antibiotics in tolerant and nontolerant bacteria.
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18
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Wi YM, Park YK, Moon C, Ryu SY, Lee H, Ki HK, Cheong HS, Son JS, Lee JS, Kwon KT, Kim JM, Ha YE, Kang CI, Ko KS, Chung DR, Peck KR, Song JH. The cefazolin inoculum effect in methicillin-susceptible Staphylococcus aureus blood isolates: their association with dysfunctional accessory gene regulator (agr). Diagn Microbiol Infect Dis 2015; 83:286-91. [PMID: 26277619 DOI: 10.1016/j.diagmicrobio.2015.07.011] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2015] [Revised: 07/15/2015] [Accepted: 07/16/2015] [Indexed: 10/23/2022]
Abstract
We evaluated the clinical significance of the cefazolin inoculum effect (CIE) in methicillin-susceptible Staphylococcus aureus (MSSA) isolates. In total, 146 isolates were recovered from patients with MSSA bacteremia at 9 hospitals in Korea. The CIE was observed in 16 MSSA isolates, and while type A was the only detected β-lactamase in MSSA isolates exhibiting the CIE, no strains expressing type B, C, or D β-lactamases exhibited this effect. The CIE was only observed in agr group III and I isolates and was significantly more common in isolates with agr dysfunction than in those with functional agr (P<0.001). Even among isolates producing type A β-lactamase, the CIE was also prevalent in isolates with dysfunctional agr than in isolates with functional agr (P=0.025). This study demonstrates an association between the CIE of MSSA isolates and agr dysfunction, in addition to those between the CIE and type A β-lactamase.
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Affiliation(s)
- Yu Mi Wi
- Division of Infectious Diseases, Samsung Changwon Hospital, Sungkyunkwan University School of Medicine, Changwon, Republic of Korea; Department of Medicine, The Graduate School of Yonsei University, Seoul, Republic of Korea
| | - Young Kyoung Park
- Department of Molecular Cell Biology, Sungkyunkwan University School of Medicine, Suwon, Republic of Korea
| | - Chisook Moon
- Division of Infectious Diseases, Inje University Busan Paik Hospital, Busan, Republic of Korea
| | - Seong Yeol Ryu
- Division of Infectious Diseases, Keimyung University Dongsan Medical Center, Daegu, Republic of Korea
| | - Hyuck Lee
- Division of Infectious Diseases, Dong-A University, Busan, Republic of Korea
| | - Hyun Kyun Ki
- Division of Infectious Diseases, Konkuk University Hospital, Seoul, Republic of Korea
| | - Hae Suk Cheong
- Division of Infectious Diseases, Konkuk University Hospital, Seoul, Republic of Korea
| | - Jun Seong Son
- Division of Infectious Diseases, Kyung Hee University Hospital at Gangdong, Seoul, Republic of Korea
| | - Jin Seo Lee
- Division of Infectious Diseases, Kangdong Sacred Heart Hospital, Hallym University School of Medicine, Seoul, Republic of Korea
| | - Ki Tae Kwon
- Division of Infectious Diseases, Daegu Fatima Hospital, Daegu, Republic of Korea
| | - June Myong Kim
- Department of Medicine, The Graduate School of Yonsei University, Seoul, Republic of Korea
| | - Young Eun Ha
- Division of Infectious Diseases, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea
| | - Cheol In Kang
- Division of Infectious Diseases, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea
| | - Kwan Soo Ko
- Department of Molecular Cell Biology, Sungkyunkwan University School of Medicine, Suwon, Republic of Korea.
| | - Doo Ryeon Chung
- Division of Infectious Diseases, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea.
| | - Kyong Ran Peck
- Division of Infectious Diseases, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea
| | - Jae-Hoon Song
- Division of Infectious Diseases, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea
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Zheng L, Yan M, Fan F, Ji Y. The Essential WalK Histidine Kinase and WalR Regulator Differentially Mediate Autolysis of Staphylococcus aureus RN4220. JOURNAL OF NATURE AND SCIENCE 2015; 1:e111. [PMID: 26052549 PMCID: PMC4457336] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The two-component regulatory system, WalR/WalK is necessary for growth of different gram-positive bacteria, including Staphylococcus aureus. In present study, we confirmed the essentiality of both the histidine kinase protein WalK and the response regulator WalR for growth using S. aureus RN4220 strain and demonstrated that the histidine kinase protein WalK and the response regulator WalR function differently in regulation of staphylococcal autolysis. The down-regulation of walR expression effectively inhibited Triton X-100-induced lysis and had a weak impact on bacterial tolerance to penicillin induced cell lysis. In contrast, the down-regulation of walK expression had no influence on either Triton X-100- or penicillin-caused autolysis. Moreover, we determined the effect of WalR and WalK on bacterial hydrolase activity using a zymogram analysis. The results showed that the cell lysate of down-regulated walR expression mutant displayed several bands of decreased cell wall hydrolytic activities; however, the down-regulation of WalK had no dramatic impact on the hydrolytic activities. Furthermore, we examined the impact of WalR on the transcription of cidA associated with staphylococcal autolysis, and the results showed that the down-regulation of WalR led to decreased transcription of cidA in the log phase of growth. Taken together, the above results suggest that the essential WalR response regulator and the essential WalK histidine kinase might differently control bacterial lysis in RN4220 strain.
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Affiliation(s)
- Li Zheng
- Department of Veterinary and Biomedical Sciences, College of Veterinary Medicine, University of Minnesota. 1971 Commonwealth Ave. St. Paul. MN 55108, USA
| | - Meiying Yan
- Department of Veterinary and Biomedical Sciences, College of Veterinary Medicine, University of Minnesota. 1971 Commonwealth Ave. St. Paul. MN 55108, USA
| | - Frank Fan
- Promega Corporation, Madison, WI 53711, USA
| | - Yinduo Ji
- Department of Veterinary and Biomedical Sciences, College of Veterinary Medicine, University of Minnesota. 1971 Commonwealth Ave. St. Paul. MN 55108, USA
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20
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Singh R, Ray P. Quorum sensing-mediated regulation of staphylococcal virulence and antibiotic resistance. Future Microbiol 2014; 9:669-81. [DOI: 10.2217/fmb.14.31] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
ABSTRACT: Accessory gene regulator (agr)-mediated quorum sensing plays a central role in staphylococcal pathogenesis. It primarily upregulates secreted virulence factors and downregulates cell surface proteins, thereby governing invasiveness of staphylococci and cell dispersal from biofilms. Except for α- and β-PSMs, which are directly controlled by AgrA, the effector functions of agr are primarily mediated by RNAIII, a regulatory RNA encoded by this operon. agr phenotype and expression considerably influence the chronicity of an infection. It has also been linked with altered susceptibility of Staphylococcus aureus against antibiotics. Four classes of S. aureus and Staphylococcus epidermidis AIPs exist based on sequence variation, and lead to inter-strain and species cross-inhibition. Certain agr classes have been associated with specific clonal complexes, disease syndromes and intermediate-susceptibility to glycopeptides. It is also being investigated as a prophylactic and therapeutic target. This article describes the presently available literature regarding the role of agr in S. aureus and S. epidermidis infections.
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Affiliation(s)
- Rachna Singh
- Department of Medical Microbiology, Postgraduate Institute of Medical Education and Research (PGIMER), Chandigarh, 160012, India
| | - Pallab Ray
- Department of Medical Microbiology, Postgraduate Institute of Medical Education and Research (PGIMER), Chandigarh, 160012, India
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21
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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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22
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Additional routes to Staphylococcus aureus daptomycin resistance as revealed by comparative genome sequencing, transcriptional profiling, and phenotypic studies. PLoS One 2013; 8:e58469. [PMID: 23554895 PMCID: PMC3598801 DOI: 10.1371/journal.pone.0058469] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2012] [Accepted: 02/05/2013] [Indexed: 12/17/2022] Open
Abstract
Daptomycin is an extensively used anti-staphylococcal agent due to the rise in methicillin-resistant Staphylococcus aureus, but the mechanism(s) of resistance is poorly understood. Comparative genome sequencing, transcriptomics, ultrastructure, and cell envelope studies were carried out on two relatively higher level (4 and 8 µg/ml−1) laboratory-derived daptomycin-resistant strains (strains CB1541 and CB1540 respectively) compared to their parent strain (CB1118; MW2). Several mutations were found in the strains. Both strains had the same mutations in the two-component system genes walK and agrA. In strain CB1540 mutations were also detected in the ribose phosphate pyrophosphokinase (prs) and polyribonucleotide nucleotidyltransferase genes (pnpA), a hypothetical protein gene, and in an intergenic region. In strain CB1541 there were mutations in clpP, an ATP-dependent protease, and two different hypothetical protein genes. The strain CB1540 transcriptome was characterized by upregulation of cap (capsule) operon genes, genes involved in the accumulation of the compatible solute glycine betaine, ure genes of the urease operon, and mscL encoding a mechanosensitive chanel. Downregulated genes included smpB, femAB and femH involved in the formation of the pentaglycine interpeptide bridge, genes involved in protein synthesis and fermentation, and spa encoding protein A. Genes altered in their expression common to both transcriptomes included some involved in glycine betaine accumulation, mscL, ure genes, femH, spa and smpB. However, the CB1541 transcriptome was further characterized by upregulation of various heat shock chaperone and protease genes, consistent with a mutation in clpP, and lytM and sceD. Both strains showed slow growth, and strongly decreased autolytic activity that appeared to be mainly due to decreased autolysin production. In contrast to previous common findings, we did not find any mutations in phospholipid biosynthesis genes, and it appears there are multiple pathways to and factors in daptomycin resistance.
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Cameron DR, Howden BP, Peleg AY. The interface between antibiotic resistance and virulence in Staphylococcus aureus and its impact upon clinical outcomes. Clin Infect Dis 2012; 53:576-82. [PMID: 21865195 DOI: 10.1093/cid/cir473] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
The ability of Staphylococcus aureus to rapidly acquire antibiotic resistance in the face of antimicrobial challenge has enabled it to remain an ongoing, significant human pathogen. Mechanisms behind the evolution of resistance in S. aureus are well documented, but the effects of these phenotypes upon virulence are less clear. By exploring available clinical and experimental data, we have shown that a number of the major steps in the evolution of antibacterial resistance in S. aureus have been accompanied by alterations in virulence. This review also highlights that further experimentation is required to fully elucidate the mechanisms involved in the interface between virulence and antibiotic resistance, with the intention of identifying novel preventative or therapeutic strategies for this important human pathogen.
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Affiliation(s)
- David R Cameron
- Department of Microbiology, Monash University, Melbourne, Australia
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Presence of genes encoding panton-valentine leukocidin is not the primary determinant of outcome in patients with hospital-acquired pneumonia due to Staphylococcus aureus. J Clin Microbiol 2012; 50:848-56. [PMID: 22205797 DOI: 10.1128/jcm.06219-11] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The impact of Panton-Valentine leukocidin (PVL) on the outcome in Staphylococcus aureus pneumonia is controversial. We genotyped S. aureus isolates from patients with hospital-acquired pneumonia (HAP) enrolled in two registrational multinational clinical trials for the genetic elements carrying pvl and 30 other virulence genes. A total of 287 isolates (173 methicillin-resistant S. aureus [MRSA] and 114 methicillin-susceptible S. aureus [MSSA] isolates) from patients from 127 centers in 34 countries for whom clinical outcomes of cure or failure were available underwent genotyping. Of these, pvl was detected by PCR and its product confirmed in 23 isolates (8.0%) (MRSA, 18/173 isolates [10.4%]; MSSA, 5/114 isolates [4.4%]). The presence of pvl was not associated with a higher risk for clinical failure (4/23 [17.4%] versus 48/264 [18.2%]; P = 1.00) or mortality. These findings persisted after adjustment for multiple potential confounding variables. No significant associations between clinical outcome and (i) presence of any of the 30 other virulence genes tested, (ii) presence of specific bacterial clone, (iii) levels of alpha-hemolysin, or (iv) delta-hemolysin production were identified. This study suggests that neither pvl presence nor in vitro level of alpha-hemolysin production is the primary determinant of outcome among patients with HAP caused by S. aureus.
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Role of ArlRS in autolysis in methicillin-sensitive and methicillin-resistant Staphylococcus aureus strains. J Bacteriol 2011; 194:759-67. [PMID: 22139508 DOI: 10.1128/jb.06261-11] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Autolysis plays an essential role in bacterial cell division and lysis with β-lactam antibiotics. Accordingly, the expression of autolysins is tightly regulated by several endogenous regulators, including ArlRS, a two component regulatory system that has been shown to negatively regulate autolysis in methicillin-sensitive Staphylococcus aureus (MSSA) strains. In this study, we found that inactivation of arlRS does not play a role in autolysis of methicillin-resistant S. aureus (MRSA) strains, such as community-acquired (CA)-MRSA strains USA300 and MW2 or the hospital-acquired (HA)-MRSA strain COL. This contrasts with MSSA strains, including Newman, SH1000, RN6390, and 8325-4, where autolysis is affected by ArlRS. We further demonstrated that the striking difference in the roles of arlRS between MSSA and MRSA strains is not due to the methicillin resistance determinant mecA. Among known autolysins and their regulators, we found that arlRS represses lytN, while no effect was seen on atl, lytM, and lytH expression in both CA- and HA-MRSA strains. Transcriptional-fusion assays showed that the agr transcripts, RNAII and RNAIII, were significantly more downregulated in the arlRS mutant of MW2 than the MSSA strain Newman. Importantly, provision of agr RNAIII in trans to the MW2 arlRS mutant via a multicopy plasmid induced autolysis in this MRSA strain. Also, the autolytic phenotype in the arlRS mutant of MSSA strain Newman could be rescued by a mutation in either atl or lytM. Together, these data showed that ArlRS impacts autolysis differently in MSSA and MRSA strains.
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Overton IM, Graham S, Gould KA, Hinds J, Botting CH, Shirran S, Barton GJ, Coote PJ. Global network analysis of drug tolerance, mode of action and virulence in methicillin-resistant S. aureus. BMC SYSTEMS BIOLOGY 2011; 5:68. [PMID: 21569391 PMCID: PMC3123200 DOI: 10.1186/1752-0509-5-68] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/16/2010] [Accepted: 05/12/2011] [Indexed: 02/08/2023]
Abstract
BACKGROUND Staphylococcus aureus is a major human pathogen and strains resistant to existing treatments continue to emerge. Development of novel treatments is therefore important. Antimicrobial peptides represent a source of potential novel antibiotics to combat resistant bacteria such as Methicillin-Resistant Staphylococcus aureus (MRSA). A promising antimicrobial peptide is ranalexin, which has potent activity against Gram-positive bacteria, and particularly S. aureus. Understanding mode of action is a key component of drug discovery and network biology approaches enable a global, integrated view of microbial physiology, including mechanisms of antibiotic killing. We developed a systems-wide functional association network approach to integrate proteome and transcriptome profiles, enabling study of drug resistance and mode of action. RESULTS The functional association network was constructed by Bayesian logistic regression, providing a framework for identification of antimicrobial peptide (ranalexin) response modules from S. aureus MRSA-252 transcriptome and proteome profiling. These signatures of ranalexin treatment revealed multiple killing mechanisms, including cell wall activity. Cell wall effects were supported by gene disruption and osmotic fragility experiments. Furthermore, twenty-two novel virulence factors were inferred, while the VraRS two-component system and PhoU-mediated persister formation were implicated in MRSA tolerance to cationic antimicrobial peptides. CONCLUSIONS This work demonstrates a powerful integrative approach to study drug resistance and mode of action. Our findings are informative to the development of novel therapeutic strategies against Staphylococcus aureus and particularly MRSA.
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Affiliation(s)
- Ian M Overton
- Biomedical Systems Analysis, MRC Human Genetics Unit, Institute of Genetics and Molecular Medicine, Western General Hospital, Crewe Road, Edinburgh EH4 2XU, UK.
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Beta-lactams interfering with PBP1 induce Panton-Valentine leukocidin expression by triggering sarA and rot global regulators of Staphylococcus aureus. Antimicrob Agents Chemother 2011; 55:3261-71. [PMID: 21502633 DOI: 10.1128/aac.01401-10] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Previous articles reported that beta-lactam antibiotics increase the expression of Staphylococcus aureus Panton-Valentine leukocidin (PVL) by activating its transcription. We investigated the mechanisms underlying the inductor effect of beta-lactams on PVL expression by determining targets and regulatory pathways possibly implicated in this process. We measured PVL production in the presence of oxacillin (nonselective), imipenem (penicillin-binding protein 1 [PBP1] selective), cefotaxime (PBP2 selective), cefaclore (PBP3 selective), and cefoxitin (PBP4 selective). In vitro, we observed increased PVL production consistent with luk-PV mRNA levels that were 20 to 25 times higher for community-acquired methicillin-resistant S. aureus (CA-MRSA) cultures treated with PBP1-binding oxacillin and imipenem than for cultures treated with other beta-lactams or no antibiotic at all. This effect was also observed in vivo, with increased PVL mRNA levels in lung tissues from CA-MRSA-infected mice treated with imipenem but not cefoxitin. To confirm the involvement of PBP1 inhibition in this pathway, PBP1 depletion by use of an inducible pbp1 antisense RNA showed a dose-dependent relationship between the level of pbp1 antisense RNA and the luk-PV mRNA level. Upon imipenem treatment of exponential-phase cultures, we observed an increased sarA mRNA level after 30 min of incubation followed by a decreased rot mRNA level after 1 to 4 h of incubation. Unlike the agr and saeRS positive regulators, which were nonessential for PVL induction by beta-lactams, the sarA (positive) and rot (negative) PVL regulators were necessary for PVL induction by imipenem. Our results suggest that antibiotics binding to PBP1 increase PVL expression by modulating sarA and rot, which are essential mediators of the inductor effect of beta-lactams on PVL expression.
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Bonde M, Højland DH, Kolmos HJ, Kallipolitis BH, Klitgaard JK. Thioridazine affects transcription of genes involved in cell wall biosynthesis in methicillin-resistant Staphylococcus aureus. FEMS Microbiol Lett 2011; 318:168-76. [PMID: 21375577 DOI: 10.1111/j.1574-6968.2011.02255.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
The antipsychotic drug thioridazine is a candidate drug for an alternative treatment of infections caused by methicillin-resistant Staphylococcus aureus (MRSA) in combination with the β-lactam antibiotic oxacillin. The drug has been shown to have the capability to resensitize MRSA to oxacillin. We have previously shown that the expression of some resistance genes is abolished after treatment with thioridazine and oxacillin. To further understand the mechanism underlying the reversal of resistance, we tested the expression of genes involved in antibiotic resistance and cell wall biosynthesis in response to thioridazine in combination with oxacillin. We observed that the oxacillin-induced expression of genes belonging to the VraSR regulon is reduced by the addition of thioridazine. The exclusion of such key factors involved in cell wall biosynthesis will most likely lead to a weakened cell wall and affect the ability of the bacteria to sustain oxacillin treatment. Furthermore, we found that thioridazine itself reduces the expression level of selected virulence genes and that selected toxin genes are not induced by thioridazine. In the present study, we find indications that the mechanism underlying reversal of resistance by thioridazine relies on decreased expression of specific genes involved in cell wall biosynthesis.
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Affiliation(s)
- Mette Bonde
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, Odense, Denmark
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Increased mortality with accessory gene regulator (agr) dysfunction in Staphylococcus aureus among bacteremic patients. Antimicrob Agents Chemother 2010; 55:1082-7. [PMID: 21173172 DOI: 10.1128/aac.00918-10] [Citation(s) in RCA: 114] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Accessory gene regulator (agr) dysfunction in Staphylococcus aureus has been associated with a longer duration of bacteremia. We aimed to assess the independent association between agr dysfunction in S. aureus bacteremia and 30-day in-hospital mortality. This retrospective cohort study included all adult inpatients with S. aureus bacteremia admitted between 1 January 2003 and 30 June 2007. Severity of illness prior to culture collection was measured using the modified acute physiology score (APS). agr dysfunction in S. aureus was identified semiquantitatively by using a δ-hemolysin production assay. Cox proportional hazard models were used to measure the association between agr dysfunction and 30-day in-hospital mortality, statistically adjusting for patient and pathogen characteristics. Among 814 patient admissions complicated by S. aureus bacteremia, 181 (22%) patients were infected with S. aureus isolates with agr dysfunction. Overall, 18% of patients with agr dysfunction in S. aureus died, compared to 12% of those with functional agr in S. aureus (P = 0.03). There was a trend toward higher mortality among patients with S. aureus with agr dysfunction (adjusted hazard ratio [HR], 1.34; 95% confidence interval [CI], 0.87 to 2.06). Among patients with the highest APS (scores of >28), agr dysfunction in S. aureus was significantly associated with mortality (adjusted HR, 1.82; 95% CI, 1.03 to 3.21). This is the first study to demonstrate an independent association between agr dysfunction and mortality among severely ill patients. The δ-hemolysin assay examining agr function may be a simple and inexpensive approach to predicting patient outcomes and potentially optimizing antibiotic therapy.
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Yu X, Zheng L, Yang J, Lei T, Ji Y. Characterization of essential enolase in Staphylococcus aureus. World J Microbiol Biotechnol 2010. [DOI: 10.1007/s11274-010-0532-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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31
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Lamichhane-Khadka R, Cantore SA, Riordan JT, Delgado A, Norman AEA, Dueñas S, Zaman S, Horan S, Wilkinson BJ, Gustafson JE. sarA inactivation reduces vancomycin-intermediate and ciprofloxacin resistance expression by Staphylococcus aureus. Int J Antimicrob Agents 2009; 34:136-41. [PMID: 19324528 DOI: 10.1016/j.ijantimicag.2009.01.018] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2008] [Revised: 11/25/2008] [Accepted: 01/16/2009] [Indexed: 11/18/2022]
Abstract
It is known that multiple genome-wide transcriptional changes often accompany the development of antimicrobial resistance and occur in response to challenge with antimicrobial agents. We now show that inactivation of the staphylococcal accessory gene regulator sarA, which controls at least tens of genes in Staphylococcus aureus, leads to dramatic reductions in vancomycin and ciprofloxacin resistance in vancomycin-intermediate and ciprofloxacin-resistant strains of S. aureus. This is particularly evident when judged by antimicrobial-gradient plate analysis or population analysis profiles. Whilst the intact sarA cistron is required for full vancomycin resistance expression by vancomycin-intermediate S. aureus (VISA), sarA expression as determined by quantitative real-time polymerase chain reaction was found to be VISA strain-dependent. Reductions in vancomycin resistance expression levels following sarA inactivation do not necessarily include an alteration in autolysis. Expression of sarR, the negative regulator of sarA, was downregulated in two VISA mutants, and transcription of the alternative sigma factor sigB was downregulated in one VISA strain. This study contributes to a growing body of evidence demonstrating the importance of loci previously identified to control virulence in the regulation of clinically relevant antibiotic resistance mechanisms.
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Trotonda MP, Xiong YQ, Memmi G, Bayer AS, Cheung AL. Role of mgrA and sarA in methicillin-resistant Staphylococcus aureus autolysis and resistance to cell wall-active antibiotics. J Infect Dis 2009; 199:209-18. [PMID: 19072553 DOI: 10.1086/595740] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
BACKGROUND We have previously shown the importance of mgrA and sarA in controlling autolysis of Staphylococcus aureus, with MgrA and SarA both being negative regulators of murein hydrolases. METHODS In this study, we analyzed the effects of mgrA and sarA on antibiotic-mediated lysis in vitro and on the responses to cell wall-active antibiotic therapy in an experimental endocarditis model by use of 2 representative MRSA strains: the laboratory strain COL and the community-acquired clinical strain MW2. RESULTS We found that mgrA and sarA independently down-regulated sarV (a marker for autolysis), although the alteration in sarV expression did not correlate directly with the autolysis profiles of single mgrA and sarA mutants. Importantly, the mgrA/sarA double mutants of both strains were more autolytic than the single mutants in vitro. We demonstrated that, despite equivalent intrinsic virulences of the parent strains and their isogenic mgrA/sarA double mutants in the endocarditis model, oxacillin and vancomycin treatment of the mgrA/sarA double mutants yielded significant reductions in vegetation bacterial densities in vivo, compared with treatment of their respective parent strains. CONCLUSIONS These results suggest that down-regulation of mgrA/sarA in combination with use of cell wall-active antibiotics may represent a novel approach to treat MRSA infections.
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Affiliation(s)
- María Pilar Trotonda
- Department of Microbiology, Dartmouth Medical School, Hanover, New Hampshire, USA
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Identification and characterization of sigma, a novel component of the Staphylococcus aureus stress and virulence responses. PLoS One 2008; 3:e3844. [PMID: 19050758 PMCID: PMC2585143 DOI: 10.1371/journal.pone.0003844] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2008] [Accepted: 10/28/2008] [Indexed: 12/16/2022] Open
Abstract
S. aureus is a highly successful pathogen that is speculated to be the most common cause of human disease. The progression of disease in S. aureus is subject to multi-factorial regulation, in response to the environments encountered during growth. This adaptive nature is thought to be central to pathogenesis, and is the result of multiple regulatory mechanisms employed in gene regulation. In this work we describe the existence of a novel S. aureus regulator, an as yet uncharacterized ECF-sigma factor (σS), that appears to be an important component of the stress and pathogenic responses of this organism. Using biochemical approaches we have shown that σS is able to associates with core-RNAP, and initiate transcription from its own coding region. Using a mutant strain we determined that σS is important for S. aureus survival during starvation, extended exposure to elevated growth temperatures, and Triton X-100 induced lysis. Coculture studies reveal that a σS mutant is significantly outcompeted by its parental strain, which is only exacerbated during prolonged growth (7 days), or in the presence of stressor compounds. Interestingly, transcriptional analysis determined that under standard conditions, S. aureus SH1000 does not initiate expression of sigS. Assays performed hourly for 72h revealed expression in typically background ranges. Analysis of a potential anti-sigma factor, encoded downstream of sigS, revealed it to have no obvious role in the upregulation of sigS expression. Using a murine model of septic arthritis, sigS-mutant infected animals lost significantly less weight, developed septic arthritis at significantly lower levels, and had increased survival rates. Studies of mounted immune responses reveal that sigS-mutant infected animals had significantly lower levels of IL-6, indicating only a weak immunological response. Finally, strains of S. aureus lacking sigS were far less able to undergo systemic dissemination, as determined by bacterial loads in the kidneys of infected animals. These results establish that σS is an important component in S. aureus fitness, and in its adaptation to stress. Additionally it appears to have a significant role in its pathogenic nature, and likely represents a key component in the S. aureus regulatory network.
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Antignac A, Sieradzki K, Tomasz A. Perturbation of cell wall synthesis suppresses autolysis in Staphylococcus aureus: evidence for coregulation of cell wall synthetic and hydrolytic enzymes. J Bacteriol 2007; 189:7573-80. [PMID: 17827298 PMCID: PMC2168716 DOI: 10.1128/jb.01048-07] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Bacterial peptidoglycan hydrolases are considered to have destructive potential, which in the presence of inhibitory concentrations of cell wall synthesis inhibitors is involved in cell lysis. Therefore, the expression and activity of autolytic enzymes must be tightly regulated in growing cells. We describe here a series of experiments undertaken to examine further the coordination between cell wall synthesis and degradation. Cell growth in the presence of subinhibitory concentrations of beta-lactam antibiotics was used to determine the effects of the partial inhibition of cell wall synthesis on the status of the autolytic system in Staphylococcus aureus. Our results revealed that, despite increased in vitro hydrolysis of cell walls by autolytic enzymes due to hypo-cross-linked peptidoglycans, cells grown in the presence of beta-lactams were dramatically less prone to autolysis as a result of decreased transcription and enzymatic activities of several major autolytic enzymes. Similar repression of autolytic enzymatic activity and transcription was also observed when cell wall synthesis was disturbed by lowering the level of transcription of pbpB, the gene encoding the major transpeptidase in S. aureus. Our data show that the perturbation of cell wall synthesis in growing cells of S. aureus induces strong repression of the autolytic system and provide evidence for transcriptional regulation between cell wall synthetic and hydrolytic enzymes.
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Affiliation(s)
- Aude Antignac
- Laboratory of Microbiology, The Rockefeller University, 1230 York Ave., New York, NY 10021, USA
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Zheng L, Yu C, Bayles K, Lasa I, Ji Y. Conditional mutation of an essential putative glycoprotease eliminates autolysis in Staphylococcus aureus. J Bacteriol 2007; 189:2734-42. [PMID: 17237169 PMCID: PMC1855823 DOI: 10.1128/jb.01806-06] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Our previous studies demonstrated that a putative Staphylococcus aureus glycoprotease (Gcp) is essential for bacterial survival, indicating that Gcp may be a novel target for developing antibacterial agents. However, the biological function of Gcp is unclear. In order to elucidate the reason that Gcp is required for growth, we examined the role of Gcp in bacterial autolysis, which is an important biological process for bacterial growth. Using both a spacp-regulated gcp expression strain and a TetR-regulated gcp antisense expression strain, we found that the down-regulation of gcp expression can effectively inhibit Triton X-100-induced lysis, eliminate penicillin- and vancomycin-caused cell lysis, and dramatically increase tolerance to hydrolases. Moreover, we determined whether resistance to lysis is due to a defect in murein hydrolase activity by using a zymogram analysis. The results showed that the cell lysate of a down-regulated gcp expression mutant displayed several bands of decreased murein hydrolytic activity. Furthermore, we explored the potential mechanism of Gcp's involvement in autolysis and demonstrated that Gcp may function independently from several key autolysins (Atl, LytM, and LytN) and regulators (ArlRS, Mgr/Rat, and CidA). Taken together, the above results indicate that the essential Gcp is involved in the modification of substrates of murein hydrolases as well as in the regulation of expression and/or activity of some murein hydrolases, which, in turn, may play important roles in bacterial viability.
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Affiliation(s)
- Li Zheng
- Department of Veterinary and Biomedical Sciences, College of Veterinary Medicine, University of Minnesota, 1971 Commonwealth Ave., St. Paul, MN 55108, USA
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Renzoni A, Barras C, François P, Charbonnier Y, Huggler E, Garzoni C, Kelley WL, Majcherczyk P, Schrenzel J, Lew DP, Vaudaux P. Transcriptomic and functional analysis of an autolysis-deficient, teicoplanin-resistant derivative of methicillin-resistant Staphylococcus aureus. Antimicrob Agents Chemother 2006; 50:3048-61. [PMID: 16940101 PMCID: PMC1563528 DOI: 10.1128/aac.00113-06] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The molecular basis of glycopeptide-intermediate S. aureus (GISA) isolates is not well defined though frequently involves phenotypes such as thickened cell walls and decreased autolysis. We have exploited an isogenic pair of teicoplanin-susceptible (strain MRGR3) and teicoplanin-resistant (strain 14-4) methicillin-resistant S. aureus strains for detailed transcriptomic profiling and analysis of altered autolytic properties. Strain 14-4 displayed markedly deficient Triton X-100-triggered autolysis compared to its teicoplanin-susceptible parent, although microarray analysis paradoxically did not reveal significant reductions in expression levels of major autolytic genes atl, lytM, and lytN, except for sle1, which showed a slight decrease. The most important paradox was a more-than-twofold increase in expression of the cidABC operon in 14-4 compared to MRGR3, which was correlated with decreased expression of autolysis negative regulators lytSR and lrgAB. In contrast, the autolysis-deficient phenotype of 14-4 was correlated with both increased expression of negative autolysis regulators (arlRS, mgrA, and sarA) and decreased expression of positive regulators (agr RNAII and RNAIII). Quantitative bacteriolytic assays and zymographic analysis of concentrated culture supernatants showed a striking reduction in Atl-derived, extracellular bacteriolytic hydrolase activities in 14-4 compared to MRGR3. This observed difference was independent of the source of cell wall substrate (MRGR3 or 14-4) used for analysis. Collectively, our results suggest that altered autolytic properties in 14-4 are apparently not driven by significant changes in the transcription of key autolytic effectors. Instead, our analysis points to alternate regulatory mechanisms that impact autolysis effectors which may include changes in posttranscriptional processing or export.
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Affiliation(s)
- Adriana Renzoni
- Service of Infectious Diseases, University Hospitals of Geneva, CH-1211 Geneva 14, Switzerland
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Riordan JT, O’Leary JO, Gustafson JE. Contributions of sigB and sarA to distinct multiple antimicrobial resistance mechanisms of Staphylococcus aureus. Int J Antimicrob Agents 2006; 28:54-61. [PMID: 16777384 PMCID: PMC3551609 DOI: 10.1016/j.ijantimicag.2006.01.013] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2005] [Accepted: 01/12/2006] [Indexed: 10/24/2022]
Abstract
Multiple antimicrobial resistance in Staphylococcus aureus can result from mutations leading to reduced susceptibility to Pine oil-based cleaners (PS(RS)) as well as following growth with the non-steroidal anti-inflammatory salicylate. We now define the contributions of the alternative sigma factor (sigB) and staphylococcal accessory regulator (sarA) to these mechanisms. We conclude that sarA plays a more prominent role than sigB in overall intrinsic multiple antimicrobial resistance. Both genes have similar effects on intrinsic vancomycin resistance, and the salicylate-inducible mechanism is not sigB- or sarA-dependent. Furthermore, analyses determined that altered expression of sigB and sarA is not responsible for the salicylate-inducible mechanism, and sarA upregulation is associated with the PS(RS) phenotype.
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Sakoulas G, Moellering RC, Eliopoulos GM. Adaptation of Methicillin-Resistant Staphylococcus aureus in the Face of Vancomycin Therapy. Clin Infect Dis 2006; 42 Suppl 1:S40-50. [PMID: 16323119 DOI: 10.1086/491713] [Citation(s) in RCA: 118] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
For the past 2 decades, vancomycin has served as the cornerstone of therapy against serious methicillin-resistant Staphylococcus aureus infections. This role is increasingly challenged by questions of efficacy, including reduced efficacy against infections caused by glycopeptide-intermediate S. aureus strains. In an evaluation of clinical glycopeptide-intermediate S. aureus isolates and serial, clinical methicillin-resistant S. aureus isolates obtained from patients receiving vancomycin for the treatment of bacteremia, we found that loss of function of the accessory gene regulator operon may confer a survival advantage to S. aureus under vancomycin selection pressure, particularly in strains with the accessory gene regulator group II genotype. Other advantages in a nosocomial setting may include enhancement of biofilm formation and promotion of physiologic changes supporting colonization. We conclude that loss of accessory gene regulator function in methicillin-resistant S. aureus might, in part, explain the decreased efficacy of vancomycin in the therapy of methicillin-resistant S. aureus bacteremia, thus highlighting the need to reevaluate the criteria of susceptibility to vancomycin.
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Affiliation(s)
- George Sakoulas
- Westchester Medical Center, Division of Infectious Diseases, New York Medical College, Valhalla, NY 10595, USA.
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Sakoulas G, Eliopoulos GM, Fowler VG, Moellering RC, Novick RP, Lucindo N, Yeaman MR, Bayer AS. Reduced susceptibility of Staphylococcus aureus to vancomycin and platelet microbicidal protein correlates with defective autolysis and loss of accessory gene regulator (agr) function. Antimicrob Agents Chemother 2005; 49:2687-92. [PMID: 15980337 PMCID: PMC1168700 DOI: 10.1128/aac.49.7.2687-2692.2005] [Citation(s) in RCA: 130] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Loss of agr function, vancomycin exposure, and abnormal autolysis have been linked with both development of the GISA phenotype and low-level resistance in vitro to thrombin-induced platelet microbicidal proteins (tPMPs). We examined the potential in vitro interrelationships among these parameters in well-characterized, isogenic laboratory-derived and clinical Staphylococcus aureus isolates. The laboratory-derived S. aureus strains included RN6607 (agrII-positive parent) and RN6607V (vancomycin-passaged variant; hetero-GISA), RN9120 (RN6607 agr::tetM; agr II knockout parent), RN9120V (vancomycin-passaged variant), and RN9120-GISA (vancomycin passaged, GISA). Two serial isolates from a vancomycin-treated patient with recalcitrant, methicillin-resistant S. aureus (MRSA) endocarditis were also studied: A5937 (agrII-positive initial isolate) and A5940 (agrII-defective/hetero-GISA isolate obtained after prolonged vancomycin administration). In vitro tPMP susceptibility phenotypes were assessed after exposure of strains to either 1 or 2 mug/ml. Triton X-100- and vancomycin-induced lysis profiles were determined spectrophotometrically. For agrII-intact strain RN6607, vancomycin exposure in vitro was associated with modest increases in vancomycin MICs and reduced killing by tPMP, but no change in lysis profiles. In contrast, vancomycin exposure of agrII-negative RN9120 yielded a hetero-GISA phenotype and was associated with defects in lysis and reduced in vitro killing by tPMP. In the clinical isolates, loss of agrII function during prolonged vancomycin therapy was accompanied by emergence of the hetero-GISA phenotype and reduced tPMP killing, with no significant change in lysis profiles. An association was identified between loss of agrII function and the emergence of hetero-GISA phenotype during either in vitro or in vivo vancomycin exposure. In vitro, these events were associated with defective lysis and reduced susceptibility to tPMP. The precise mechanism(s) underlying these findings is the subject of current investigations.
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Affiliation(s)
- George Sakoulas
- Westchester Medical Center, New York Medical College, Valhalla, New York 10595, USA
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40
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Mashburn LM, Jett AM, Akins DR, Whiteley M. Staphylococcus aureus serves as an iron source for Pseudomonas aeruginosa during in vivo coculture. J Bacteriol 2005; 187:554-66. [PMID: 15629927 PMCID: PMC543556 DOI: 10.1128/jb.187.2.554-566.2005] [Citation(s) in RCA: 218] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Pseudomonas aeruginosa is a gram-negative opportunistic human pathogen often infecting the lungs of individuals with the heritable disease cystic fibrosis and the peritoneum of individuals undergoing continuous ambulatory peritoneal dialysis. Often these infections are not caused by colonization with P. aeruginosa alone but instead by a consortium of pathogenic bacteria. Little is known about growth and persistence of P. aeruginosa in vivo, and less is known about the impact of coinfecting bacteria on P. aeruginosa pathogenesis and physiology. In this study, a rat dialysis membrane peritoneal model was used to evaluate the in vivo transcriptome of P. aeruginosa in monoculture and in coculture with Staphylococcus aureus. Monoculture results indicate that approximately 5% of all P. aeruginosa genes are differentially regulated during growth in vivo compared to in vitro controls. Included in this analysis are genes important for iron acquisition and growth in low-oxygen environments. The presence of S. aureus caused decreased transcription of P. aeruginosa iron-regulated genes during in vivo coculture, indicating that the presence of S. aureus increases usable iron for P. aeruginosa in this environment. We propose a model where P. aeruginosa lyses S. aureus and uses released iron for growth in low-iron environments.
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Affiliation(s)
- Lauren M Mashburn
- Department of Periodontics, The University of Oklahoma Health Sciences Center, Oklahoma City, OK 7310, USA
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41
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Koehl JL, Muthaiyan A, Jayaswal RK, Ehlert K, Labischinski H, Wilkinson BJ. Cell wall composition and decreased autolytic activity and lysostaphin susceptibility of glycopeptide-intermediate Staphylococcus aureus. Antimicrob Agents Chemother 2004; 48:3749-57. [PMID: 15388430 PMCID: PMC521931 DOI: 10.1128/aac.48.10.3749-3757.2004] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The cell wall composition and autolytic properties of passage-selected glycopeptide-intermediate Staphylococcus aureus (GISA) isolates and their parent strains were studied in order to investigate the mechanism of decreased vancomycin susceptibility. GISA had relatively modest changes in peptidoglycan composition involving peptidoglycan interpeptide bridges and somewhat decreased cross-linking compared to that of parent strains. The cell wall phosphorus content of GISA strains was lower than that of susceptible parent strains, indicating somewhat lower wall teichoic acid levels in the GISA strains. Similar to whole cells, isolated crude cell walls retaining autolytic activity of GISA had drastically reduced autolytic activity compared to that of parent strains, and this arose early in the development of the GISA phenotype. This was due to an alteration in the autolytic enzymes of GISA as revealed by normal susceptibility of GISA-purified cell walls to parental strain autolysin extract and lower activity and altered peptidoglycan hydrolase activity profiles in GISA autolysin extracts compared to those of parent strains. Northern blot analysis indicated that expression of atl, the major autolysin gene, was significantly downregulated in a GISA strain compared to that of its parent strain. In contrast to whole cells, which showed decreased lysostaphin susceptibility, purified cell walls of GISA showed increased susceptibility to lysostaphin. We suggest that in our GISA strains, decreased autolytic activity is involved in the tolerance of vancomycin and the activities of endogenous autolysins are important in conferring sensitivity to lysostaphin on whole cells.
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Affiliation(s)
- Jennifer L Koehl
- Microbiology Group, Department of Biological Sciences, Illinois State University, Normal, IL 61790-4120, USA
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42
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O'Leary JO, Langevin MJ, Price CTD, Blevins JS, Smeltzer MS, Gustafson JE. Effects of sarA inactivation on the intrinsic multidrug resistance mechanism of Staphylococcus aureus. FEMS Microbiol Lett 2004. [PMID: 15321676 DOI: 10.1111/j.1574-6968.2004.tb09710.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
The sarA locus of Staphylococccus aureus regulates the synthesis of over 100 genes on the S. aureus chromosome. We now report the effects of sarA inactivation on intrinsic multidrug resistance expression by S. aureus. In a strain-dependent fashion, sarA::kan mutants of three unrelated strains of S. aureus demonstrated significantly increased susceptibility to five or more of the following substances: the antibiotics ciprofloxacin, fusidic acid, and vancomycin; the DNA-intercalating agent ethidium; and four common household cleaner formulations. In addition, all three sarA::kan mutants demonstrated significantly increased accumulation of ciprofloxacin and one sarA::kan mutant demonstrated increased ethidium accumulation. Our data therefore indicate that sarA plays a role in the intrinsic multidrug resistance mechanism expressed by S. aureus, in part by regulating drug accumulation.
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Affiliation(s)
- Jessica O O'Leary
- Microbiology Group, Department of Biology, New Mexico State University, Las Cruces, NM 88003-8001, USA
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43
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Manna AC, Ingavale SS, Maloney M, van Wamel W, Cheung AL. Identification of sarV (SA2062), a new transcriptional regulator, is repressed by SarA and MgrA (SA0641) and involved in the regulation of autolysis in Staphylococcus aureus. J Bacteriol 2004; 186:5267-80. [PMID: 15292128 PMCID: PMC490931 DOI: 10.1128/jb.186.16.5267-5280.2004] [Citation(s) in RCA: 97] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The expression of genes involved in the pathogenesis of Staphylococcus aureus is known to be controlled by global regulatory loci, including agr, sarA, sae, arlRS, lytSR, and sarA-like genes. Here we described a novel transcriptional regulator called sarV of the SarA protein family. The transcription of sarV is low or undetectable under in vitro conditions but is significantly augmented in sarA and mgrA (norR or rat) (SA0641) mutants. The sarA and mgrA genes act as repressors of sarV expression, as confirmed by transcriptional fusion and Northern analysis data. Purified SarA and MgrA proteins bound specifically to separate regions of the sarV promoter as determined by gel shift and DNase I footprinting assays. The expression of 19 potential target genes involved in autolysis and virulence, phenotypes affected by sarA and mgrA, was evaluated in an isogenic sarV mutant pair. Our data indicated that the sarV gene product played a role regulating some virulence genes and more genes involved in autolysis. The sarV mutant was more resistant to Triton X-100 and penicillin-induced lysis compared to the wild type and the sarA mutant, whereas hyperexpression of sarV in the parental strain or the sarV mutant rendered the resultant strain highly susceptible to lysis. Zymographic analysis of murein hydrolase activity revealed that inactivation of the sarV gene results in decreased extracellular murein hydrolase activity compared to that of wild-type S. aureus. We propose that sarV may be part of the common pathway by which mgrA and sarA gene products control autolysis in S. aureus.
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Affiliation(s)
- Adhar C Manna
- Department of Microbiology, Dartmouth Medical School, Hanover, NH 03755, USA.
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Rice KC, Patton T, Yang SJ, Dumoulin A, Bischoff M, Bayles KW. Transcription of the Staphylococcus aureus cid and lrg murein hydrolase regulators is affected by sigma factor B. J Bacteriol 2004; 186:3029-37. [PMID: 15126464 PMCID: PMC400629 DOI: 10.1128/jb.186.10.3029-3037.2004] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
The Staphylococcus aureus lrg and cid loci are homologous operons that have been shown to regulate murein hydrolase activity and affect sensitivity to penicillin. Although the mode of action of these operons has not been demonstrated, a model based on the similarities of the lrgA and cidA gene products to the bacteriophage holin family of proteins has been proposed. In this study, the transcription organization and regulation of these operons were examined by Northern blot analyses. Unexpectedly, cidB and a gene located immediately downstream, designated cidC, were found to be cotranscribed on a 2.7-kb transcript. Maximal cidBC transcription occurred during early exponential growth, and high-level transcription of cidBC was dependent on the rsbU-mediated activation of the alternative sigma factor B (sigmaB). In contrast, lrgAB transcription in stationary phase was negatively regulated by sigmaB. Although cidABC transcription was not detected by Northern blot analysis, reverse transcriptase PCR revealed that these genes are also cotranscribed as a single RNA message in early exponential growth. Primer extension analysis revealed the presence of two cidBC transcription start sites, but no apparent sigmaB-dependent promoter consensus sequence was identified in these regions. The rsbU gene was also shown to have a positive impact on murein hydrolase activity but a negligible effect on sensitivity to penicillin-induced killing. These results suggest that the lrgAB and cidBC genes may be part of the S. aureus sigmaB-controlled stress regulon.
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Affiliation(s)
- Kelly C Rice
- Department of Microbiology, Molecular Biology, and Biochemistry, University of Idaho, Moscow, Idaho 83844-3052, USA
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Abstract
The Staphylococcus aureus cid and lrg operons have been shown to encode putative membrane proteins that are involved in the regulation of murein hydrolase activity and penicillin tolerance. Cid proteins enhance murein hydrolase activity and penicillin sensitivity, whereas Lrg proteins have an inhibitory effect on these processes. It has been proposed that the Cid and Lrg proteins function in a way analogous to bacteriophage-encoded holins and antiholins, respectively, which control the timing of bacteriophage-induced lysis. This article explores the possibility that the Cid-Lrg regulatory system controls bacterial programmed cell death using a molecular strategy that it is functionally analogous to that mediated by the eukaryotic Bcl-2 family of apoptosis regulatory proteins.
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Affiliation(s)
- Kenneth W Bayles
- Department of Microbiology, Molecular Biology and Biochemistry, University of Idaho, Moscow, ID 83844-3052, USA.
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Ingavale SS, Van Wamel W, Cheung AL. Characterization of RAT, an autolysis regulator in Staphylococcus aureus. Mol Microbiol 2003; 48:1451-66. [PMID: 12791130 DOI: 10.1046/j.1365-2958.2003.03503.x] [Citation(s) in RCA: 106] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
In trying to identify genetic loci involved in the regulation of cap5 genes in Staphylococcus aureus, we isolated a transposon mutant that exhibited a growth defect, enhanced autolysis and increased sensitivity to Triton X-100 and penicillin, attributable in part to increased murein hydrolase activity. Analysis of the chromosomal sequence flanking the transposon insertion site revealed that the gene disrupted in the mutant encodes an open reading frame of 147 amino acids. We named this gene rat, which stands for regulator of autolytic activity. Sequence analysis indicated that Rat is homologous to the MarR and, to a lesser extent, the SarA protein families. Mutations in rat resulted in decreased expression of known autolytic regulators lytSR, lrgAB and arlRS. Gel shift studies indicated that Rat binds to the lytRS and arlRS promoters, thus confirming Rat as a DNA-binding protein to these known repressors of autolytic activity. As anticipated, rat appears to be a negative regulator of autolysin genes including lytM and lytN. These data suggest that the rat gene product is an important regulator of autolytic activity in S. aureus.
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Affiliation(s)
- S S Ingavale
- Department of Microbiology, Dartmouth Medical School, Hanover, NH 03755, USA
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Cordwell SJ, Larsen MR, Cole RT, Walsh BJ. Comparative proteomics of Staphylococcus aureus and the response of methicillin-resistant and methicillin-sensitive strains to Triton X-100. MICROBIOLOGY (READING, ENGLAND) 2002; 148:2765-2781. [PMID: 12213923 DOI: 10.1099/00221287-148-9-2765] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Proteomics is a powerful tool for analysing differences in gene expression between bacterial strains with alternate phenotypes. Staphylococcus aureus strains are grouped on the basis of their sensitivity to methicillin. Two-dimensional gel electrophoresis was combined with MS to compare the protein profiles of S. aureus strains COL (methicillin-resistant) and 8325 (methicillin-sensitive). Reference mapping via this approach identified 377 proteins that corresponded to 266 distinct ORFs. Amongst these identified proteins were 14 potential virulence factors. The production of 41 'hypothetical' proteins was confirmed, and eight of these appeared to be unique to S. aureus. Strain COL displayed 12 protein spots, which included alkaline-shock protein 23 (Asp23) and cold-shock proteins CspABC, which either were not present in strain 8325 or were present at a significantly lower intensity in this strain. Comparative maps were used to characterize the S. aureus response to treatment with Triton X-100 (TX-100), a detergent that has been shown to reduce methicillin resistance independently of an interaction with the mecA-encoded penicillin-binding protein 2a. In response to growth of the bacteria in the presence of TX-100, 44 protein spots showed altered levels of abundance, and 11 of these spots were found only in COL. The products of genes regulated by sigma(B) (the alternative sigma factor), including Asp23 and three proteins of unknown function, and SarA (a regulator of virulence genes) were shown to be present at significantly altered levels. SarA production was induced in TX-100-treated cultures. A protein of the sigma(B) operon, RsbV, was only detected in COL and its production was down-regulated in COL when the strain was treated with TX-100, whereas RsbW was present at reduced levels in both strains. Upon growth of both strains in the presence of TX-100, no effects on the production of the essential methicillin-resistance factor FemA were detected, whereas phosphoglucosamine mutase (GlmM) production was reduced in COL alone. This study suggests that proteins of the sigma(B) and sarA regulons, as well as other factors, are involved in methicillin resistance in S. aureus.
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Affiliation(s)
- Stuart J Cordwell
- Australian Proteome Analysis Facility, Level 4, Building F7B, Macquarie University, Sydney, Australia21091
| | - Martin R Larsen
- Australian Proteome Analysis Facility, Level 4, Building F7B, Macquarie University, Sydney, Australia21091
| | - Rebecca T Cole
- Australian Proteome Analysis Facility, Level 4, Building F7B, Macquarie University, Sydney, Australia21091
| | - Bradley J Walsh
- Australian Proteome Analysis Facility, Level 4, Building F7B, Macquarie University, Sydney, Australia21091
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Wen ZT, Burne RA. Functional genomics approach to identifying genes required for biofilm development by Streptococcus mutans. Appl Environ Microbiol 2002; 68:1196-203. [PMID: 11872468 PMCID: PMC123778 DOI: 10.1128/aem.68.3.1196-1203.2002] [Citation(s) in RCA: 179] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Streptococcus mutans, the primary etiological agent of human dental caries, is an obligate biofilm-forming bacterium. The goals of this study were to identify the gene(s) required for biofilm formation by this organism and to elucidate the role(s) that some of the known global regulators of gene expression play in controlling biofilm formation. In S. mutans UA159, the brpA gene (for biofilm regulatory protein) was found to encode a novel protein of 406 amino acid residues. A strain carrying an insertionally inactivated copy of brpA formed longer chains than did the parental strain, aggregated in liquid culture, and was unable to form biofilms as shown by an in vitro biofilm assay. A putative homologue of the enzyme responsible for synthesis of autoinducer II (AI-2) of the bacterial quorum-sensing system was also identified in S. mutans UA159, but insertional inactivation of the gene (luxS(Sm)) did not alter colony or cell morphology or diminish the capacity of S. mutans to form biofilms. We also examined the role of the homologue of the Bacillus subtilis catabolite control protein CcpA in S. mutans in biofilm formation, and the results showed that loss of CcpA resulted in about a 60% decrease in the ability to form biofilms on an abiotic surface. From these data, we conclude that CcpA and BrpA may regulate genes that are required for stable biofilm formation by S. mutans.
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Affiliation(s)
- Zezhang T Wen
- Department of Oral Biology, College of Dentistry, University of Florida, Gainesville, FL 32610, USA
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Penyige A, Matkó J, Deák E, Bodnár A, Barabás G. Depolarization of the membrane potential by beta-lactams as a signal to induce autolysis. Biochem Biophys Res Commun 2002; 290:1169-75. [PMID: 11811985 DOI: 10.1006/bbrc.2001.6317] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The effect of beta-lactam antibiotics that are known to inhibit cell wall biosynthesis and induce cell wall autolysis on the electrophysiological state of the plasma membrane in Streptomyces griseus was studied. Addition of various beta-lactam antibiotics induced a dose- and growth-stage-dependent depolarization of the membrane potential of Streptomyces griseus. The hydrolyzed biologically inactive derivative penicilloic acid had no depolarizing effect on the membrane potential. The ionophore gramicidin D, while depolarizing the membrane potential, also induced a dose-dependent increase in cell wall lysis. These observations suggest that alteration of the transmembrane potential could be an important signal in triggering cell wall autolysis of S. griseus.
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Affiliation(s)
- András Penyige
- University of Debrecen, Medical and Health Science Center, Debrecen, H-4012, Hungary.
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50
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Affiliation(s)
- A L Koch
- Department of Biology, Indiana University, 1001 E. Third St., Bloomington, IN 47405-6801, USA.
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