1
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Lucidi M, Visaggio D, Migliaccio A, Capecchi G, Visca P, Imperi F, Zarrilli R. Pathogenicity and virulence of Acinetobacter baumannii: Factors contributing to the fitness in healthcare settings and the infected host. Virulence 2024; 15:2289769. [PMID: 38054753 PMCID: PMC10732645 DOI: 10.1080/21505594.2023.2289769] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2023] [Accepted: 11/27/2023] [Indexed: 12/07/2023] Open
Abstract
Acinetobacter baumannii is a common cause of healthcare-associated infections and hospital outbreaks, particularly in intensive care units. Much of the success of A. baumannii relies on its genomic plasticity, which allows rapid adaptation to adversity and stress. The capacity to acquire novel antibiotic resistance determinants and the tolerance to stresses encountered in the hospital environment promote A. baumannii spread among patients and long-term contamination of the healthcare setting. This review explores virulence factors and physiological traits contributing to A. baumannii infection and adaptation to the hospital environment. Several cell-associated and secreted virulence factors involved in A. baumannii biofilm formation, cell adhesion, invasion, and persistence in the host, as well as resistance to xeric stress imposed by the healthcare settings, are illustrated to give reasons for the success of A. baumannii as a hospital pathogen.
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Affiliation(s)
- Massimiliano Lucidi
- Department of Science, Roma Tre University, Rome, Italy
- NBFC, National Biodiversity Future Center, Palermo, Italy
| | - Daniela Visaggio
- Department of Science, Roma Tre University, Rome, Italy
- NBFC, National Biodiversity Future Center, Palermo, Italy
- Santa Lucia Foundation IRCCS, Rome, Italy
| | | | | | - Paolo Visca
- Department of Science, Roma Tre University, Rome, Italy
- NBFC, National Biodiversity Future Center, Palermo, Italy
- Santa Lucia Foundation IRCCS, Rome, Italy
| | - Francesco Imperi
- Department of Science, Roma Tre University, Rome, Italy
- NBFC, National Biodiversity Future Center, Palermo, Italy
- Santa Lucia Foundation IRCCS, Rome, Italy
| | - Raffaele Zarrilli
- Department of Public Health, University of Naples Federico II, Naples, Italy
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2
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Bae JY, Yun I, Jun KI, Kim CJ, Lee M, Choi HJ. Association between Pneumonia Development and Virulence Gene Expression in Carbapenem-Resistant Acinetobacter baumannii Isolated from Clinical Specimens. THE CANADIAN JOURNAL OF INFECTIOUS DISEASES & MEDICAL MICROBIOLOGY = JOURNAL CANADIEN DES MALADIES INFECTIEUSES ET DE LA MICROBIOLOGIE MEDICALE 2023; 2023:8265683. [PMID: 38156310 PMCID: PMC10754638 DOI: 10.1155/2023/8265683] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/16/2023] [Revised: 11/15/2023] [Accepted: 12/13/2023] [Indexed: 12/30/2023]
Abstract
We investigated the virulence gene expression of carbapenem-resistant Acinetobacter baumanii (CRAB) isolated from the respiratory samples of patients with CRAB pneumonia and those with CRAB colonization to identify the virulence genes contributing to CRAB pneumonia's development and mortality. Patients with CRAB identified from respiratory specimens were screened at a tertiary university hospital between January 2018 and January 2019. Patients were classified into CRAB pneumonia or CRAB colonization groups according to predefined clinical criteria. A. baumannii isolated from respiratory specimens was examined for the expression levels of ompA, uspA, hfq, hisF, feoA, and bfnL by quantitative reverse-transcription polymerase chain reaction. Among 156 patients with CRAB from respiratory specimens, 17 and 24 met the criteria for inclusion in the pneumonia and colonization groups, respectively. The expression level of ompA was significantly higher in the pneumonia group than in the colonization group (1.45 vs. 0.63, P=0.03). The expression levels of ompA (1.97 vs. 0.86, P=0.02), hisF (1.06 vs. 0.10, P < 0.01), uspA (1.62 vs. 1.01, P < 0.01), and bfnL (3.14 vs. 2.14, P=0.03) were significantly higher in patients with 30-day mortality than in the surviving patients. Elevated expression of hisF (adjusted odds ratio = 5.93, P=0.03) and uspA (adjusted odds ratio = 7.36, P=0.02) were associated with 30-day mortality after adjusting for age and the Charlson score. uspA and hisF may serve as putative targets for novel therapeutic strategies.
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Affiliation(s)
- Ji Yun Bae
- Department of Internal Medicine, Ewha Womans University Mokdong Hospital, Seoul, Republic of Korea
- Ewha Education and Research Center for Infection, Seoul, Republic of Korea
- Department of Internal Medicine, Ewha Womans University Seoul Hospital, Seoul, Republic of Korea
| | - Ina Yun
- Ewha Education and Research Center for Infection, Seoul, Republic of Korea
| | - Kang Il Jun
- Ewha Education and Research Center for Infection, Seoul, Republic of Korea
- Department of Internal Medicine, Ewha Womans University Seoul Hospital, Seoul, Republic of Korea
| | - Chung-Jong Kim
- Ewha Education and Research Center for Infection, Seoul, Republic of Korea
- Department of Internal Medicine, Ewha Womans University Seoul Hospital, Seoul, Republic of Korea
| | - Miae Lee
- Ewha Education and Research Center for Infection, Seoul, Republic of Korea
- Department of Laboratory Medicine, Ewha Womans University Mokdong Hospital, Seoul, Republic of Korea
- Department of Laboratory Medicine, Seegene Medical Foundation, Seoul, Republic of Korea
| | - Hee Jung Choi
- Department of Internal Medicine, Ewha Womans University Mokdong Hospital, Seoul, Republic of Korea
- Ewha Education and Research Center for Infection, Seoul, Republic of Korea
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3
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Bjånes E, Koh T, Qayum T, Zurich R, McCabe S, Hampel K, Cartwright L, Nizet V. Exploring Roles of the Polysaccharide Capsule in Pathogenesis of Hypervirulent Acinetobacter baumannii Clinical Isolate Lac-4. Antibiotics (Basel) 2023; 13:10. [PMID: 38275320 PMCID: PMC10812722 DOI: 10.3390/antibiotics13010010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2023] [Revised: 12/15/2023] [Accepted: 12/18/2023] [Indexed: 01/27/2024] Open
Abstract
The frequently multidrug-resistant bacterial pathogen Acinetobacter baumannii is a leading cause of nosocomial infections, including ventilator-associated pneumonia, such that the World Health Organization and US Centers for Disease Control and Prevention have declared it a top priority candidate for novel drug development. Nearly all clinical A. baumannii strains express a thick surface polysaccharide capsule that protects against desiccation, host defenses, and disinfectants. In this study, we investigated the contribution of the polysaccharide capsule to virulence caused by the A. baumannii clinical isolate Ab Lac-4, which is rare in its ability to cause pneumonia and disseminated sepsis in healthy mice. We assessed the role of the capsule in wildtype Lac-4 (WT) by generating a premature stop codon in wza, which codes for the polysaccharide export protein. The wza# mutant was hypersensitive to killing by complement, whole blood, and healthy human neutrophils compared to WT and a revertant mutant (wza-Rev). Furthermore, the wza# mutant was highly attenuated in murine sepsis and unable to disseminate from the lungs during pneumonia. This study reinforces the capsule as a key contributor to Ab Lac-4 hypervirulence.
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Affiliation(s)
- Elisabet Bjånes
- Division of Host-Microbe Systems and Therapeutics, Department of Pediatrics, University of California San Diego, La Jolla, CA 92093, USA; (T.K.); (T.Q.); (R.Z.); (S.M.); (K.H.); (L.C.)
| | - Truman Koh
- Division of Host-Microbe Systems and Therapeutics, Department of Pediatrics, University of California San Diego, La Jolla, CA 92093, USA; (T.K.); (T.Q.); (R.Z.); (S.M.); (K.H.); (L.C.)
| | - Tariq Qayum
- Division of Host-Microbe Systems and Therapeutics, Department of Pediatrics, University of California San Diego, La Jolla, CA 92093, USA; (T.K.); (T.Q.); (R.Z.); (S.M.); (K.H.); (L.C.)
| | - Raymond Zurich
- Division of Host-Microbe Systems and Therapeutics, Department of Pediatrics, University of California San Diego, La Jolla, CA 92093, USA; (T.K.); (T.Q.); (R.Z.); (S.M.); (K.H.); (L.C.)
| | - Sinead McCabe
- Division of Host-Microbe Systems and Therapeutics, Department of Pediatrics, University of California San Diego, La Jolla, CA 92093, USA; (T.K.); (T.Q.); (R.Z.); (S.M.); (K.H.); (L.C.)
| | - Kegan Hampel
- Division of Host-Microbe Systems and Therapeutics, Department of Pediatrics, University of California San Diego, La Jolla, CA 92093, USA; (T.K.); (T.Q.); (R.Z.); (S.M.); (K.H.); (L.C.)
| | - Lisa Cartwright
- Division of Host-Microbe Systems and Therapeutics, Department of Pediatrics, University of California San Diego, La Jolla, CA 92093, USA; (T.K.); (T.Q.); (R.Z.); (S.M.); (K.H.); (L.C.)
| | - Victor Nizet
- Division of Host-Microbe Systems and Therapeutics, Department of Pediatrics, University of California San Diego, La Jolla, CA 92093, USA; (T.K.); (T.Q.); (R.Z.); (S.M.); (K.H.); (L.C.)
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, La Jolla, CA 92093, USA
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4
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Maure A, Robino E, Van der Henst C. The intracellular life of Acinetobacter baumannii. Trends Microbiol 2023; 31:1238-1250. [PMID: 37487768 DOI: 10.1016/j.tim.2023.06.007] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2022] [Revised: 06/16/2023] [Accepted: 06/23/2023] [Indexed: 07/26/2023]
Abstract
Acinetobacter baumannii is a Gram-negative opportunistic bacterium responsible for nosocomial and community-acquired infections. This pathogen is globally disseminated and associated with high levels of antibiotic resistance, which makes it an important threat to human health. Recently, new evidence showed that several A. baumannii isolates can survive and proliferate within eukaryotic professional and/or nonprofessional phagocytic cells, with in vivo consequences. This review provides updated information and describes the tools that A. baumannii possesses to adhere, colonize, and replicate in host cells. Additionally, we emphasize the high genetic and phenotypic heterogeneity detected amongst A. baumannii isolates and its impact on the bacterial intracellular features. We also discuss the need for standardized methods to characterize this pathogen robustly and consequently consider some strains as facultative intracellular bacteria.
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Affiliation(s)
- Alexandra Maure
- Microbial Resistance and Drug Discovery, VIB-VUB Center for Structural Biology, VIB, Flanders Institute for Biotechnology, Brussels, Belgium; Structural Biology Brussels, Vrije Universiteit Brussel (VUB), Brussels, Belgium
| | - Etienne Robino
- Microbial Resistance and Drug Discovery, VIB-VUB Center for Structural Biology, VIB, Flanders Institute for Biotechnology, Brussels, Belgium; Structural Biology Brussels, Vrije Universiteit Brussel (VUB), Brussels, Belgium
| | - Charles Van der Henst
- Microbial Resistance and Drug Discovery, VIB-VUB Center for Structural Biology, VIB, Flanders Institute for Biotechnology, Brussels, Belgium; Structural Biology Brussels, Vrije Universiteit Brussel (VUB), Brussels, Belgium.
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5
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Artuso I, Poddar H, Evans BA, Visca P. Genomics of Acinetobacter baumannii iron uptake. Microb Genom 2023; 9:mgen001080. [PMID: 37549061 PMCID: PMC10483418 DOI: 10.1099/mgen.0.001080] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2023] [Accepted: 07/10/2023] [Indexed: 08/09/2023] Open
Abstract
Iron is essential for growth in most bacteria due to its redox activity and its role in essential metabolic reactions; it is a cofactor for many bacterial enzymes. The bacterium Acinetobacter baumannii is a multidrug-resistant nosocomial pathogen. A. baumannii responds to low iron availability imposed by the host through the exploitation of multiple iron-acquisition strategies, which are likely to deliver iron to the cell under a variety of environmental conditions, including human and animal infection. To date, six different gene clusters for active iron uptake have been described in A. baumannii , encoding protein systems involved in (i) ferrous iron uptake (feo ); (ii) haem uptake (hemT and hemO ); and (iii) synthesis and transport of the baumannoferrin(s) (bfn ), acinetobactin (bas /bau ) and fimsbactin(s) (fbs ) siderophores. Here we describe the structure, distribution and phylogeny of iron-uptake gene clusters among >1000 genotypically diverse A. baumannii isolates, showing that feo , hemT , bfn and bas /bau clusters are very prevalent across the dataset, whereas the additional haem-uptake system hemO is only present in a portion of the dataset and the fbs gene cluster is very rare. Since the expression of multiple iron-uptake clusters can be linked to virulence, the presence of the additional haem-uptake system hemO may have contributed to the success of some A. baumannii clones.
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Affiliation(s)
- Irene Artuso
- Department of Science, Roma Tre University, Viale G. Marconi 446, 00146 Rome, Italy
| | - Harsh Poddar
- Department of Science, Roma Tre University, Viale G. Marconi 446, 00146 Rome, Italy
| | - Benjamin A. Evans
- Norwich Medical School, University of East Anglia, Rosalind Franklin Road, Norwich Research Park, Norwich, NR4 7UQ, UK
| | - Paolo Visca
- Department of Science, Roma Tre University, Viale G. Marconi 446, 00146 Rome, Italy
- Fondazione Santa Lucia IRCCS, Via Ardeatina, 306/354, 00179 Rome, Italy
- National Biodiversity Future Centre, Palermo 90133, Italy
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6
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Ren X, Palmer LD. Acinetobacter Metabolism in Infection and Antimicrobial Resistance. Infect Immun 2023:e0043322. [PMID: 37191522 DOI: 10.1128/iai.00433-22] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/17/2023] Open
Abstract
Acinetobacter infections have high rates of mortality due to an increasing incidence of infections by multidrug-resistant (MDR) and extensively-drug-resistant (XDR) strains. Therefore, new therapeutic strategies for the treatment of Acinetobacter infections are urgently needed. Acinetobacter spp. are Gram-negative coccobacilli that are obligate aerobes and can utilize a wide variety of carbon sources. Acinetobacter baumannii is the main cause of Acinetobacter infections, and recent work has identified multiple strategies A. baumannii uses to acquire nutrients and replicate in the face of host nutrient restriction. Some host nutrient sources also serve antimicrobial and immunomodulatory functions. Hence, understanding Acinetobacter metabolism during infection may provide new insights into novel infection control measures. In this review, we focus on the role of metabolism during infection and in resistance to antibiotics and other antimicrobial agents and discuss the possibility that metabolism may be exploited to identify novel targets to treat Acinetobacter infections.
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Affiliation(s)
- Xiaomei Ren
- Department of Microbiology and Immunology, University of Illinois Chicago, Chicago, Illinois, USA
| | - Lauren D Palmer
- Department of Microbiology and Immunology, University of Illinois Chicago, Chicago, Illinois, USA
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7
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Abstract
Iron (Fe) plays important roles in both essential cellular processes and virulence pathways for many bacteria. Consequently, Fe withholding by the human innate immune system is an effective form of defense against bacterial infection. In this Perspective, we review recent studies that have established a foundation for our understanding of the impact of the metal-sequestering host defense protein calprotectin (CP) on bacterial Fe homeostasis. We also discuss two recently uncovered strategies for bacterial adaptation to Fe withholding by CP. Together, these studies provide insight into how Fe sequestration by CP affects bacterial pathogens that include Pseudomonas aeruginosa, Acinetobacter baumannii, and Staphylococcus aureus. Overall, recent studies suggest that Fe withholding by CP may have implications for bacterial survival and virulence in the host, and further explorations that directly address this possibility present an important area for discovery.
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Affiliation(s)
- Adunoluwa O. Obisesan
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Emily M. Zygiel
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Elizabeth M. Nolan
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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8
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Monteith AJ, Skaar EP. The impact of metal availability on immune function during infection. Trends Endocrinol Metab 2021; 32:916-928. [PMID: 34483037 PMCID: PMC8516721 DOI: 10.1016/j.tem.2021.08.004] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/15/2021] [Revised: 08/12/2021] [Accepted: 08/13/2021] [Indexed: 12/16/2022]
Abstract
Nutrient transition metals are required cofactors for many proteins to perform functions necessary for life. As such, the concentration of nutrient metals is carefully maintained to retain critical biological processes while limiting toxicity. During infection, invading bacterial pathogens must acquire essential metals, such as zinc, manganese, iron, and copper, from the host to colonize and cause disease. To combat this, the host exploits the essentiality and toxicity of nutrient metals by producing factors that limit metal availability, thereby starving pathogens or accumulating metals in excess to intoxicate the pathogen in a process termed 'nutritional immunity'. As a result of inflammation, a heterogeneous environment containing both metal-replete and -deplete niches is created, in which nutrient metal availability may have an underappreciated role in regulating immune cell function during infection. How the host manipulates nutrient metal availability during infection, and the downstream effects that nutrient metals and metal-sequestering proteins have on immune cell function, are discussed in this review.
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Affiliation(s)
- Andrew J Monteith
- Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Eric P Skaar
- Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center, Nashville, TN, USA; Vanderbilt Institute for Infection, Immunology, & Inflammation, Vanderbilt University Medical Center, Nashville, TN, USA.
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9
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Bateman TJ, Shah M, Ho TP, Shin HE, Pan C, Harris G, Fegan JE, Islam EA, Ahn SK, Hooda Y, Gray-Owen SD, Chen W, Moraes TF. A Slam-dependent hemophore contributes to heme acquisition in the bacterial pathogen Acinetobacter baumannii. Nat Commun 2021; 12:6270. [PMID: 34725337 PMCID: PMC8560813 DOI: 10.1038/s41467-021-26545-9] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2019] [Accepted: 10/06/2021] [Indexed: 12/02/2022] Open
Abstract
Nutrient acquisition systems are often crucial for pathogen growth and survival during infection, and represent attractive therapeutic targets. Here, we study the protein machinery required for heme uptake in the opportunistic pathogen Acinetobacter baumannii. We show that the hemO locus, which includes a gene encoding the heme-degrading enzyme, is required for high-affinity heme acquisition from hemoglobin and serum albumin. The hemO locus includes a gene coding for a heme scavenger (HphA), which is secreted by a Slam protein. Furthermore, heme uptake is dependent on a TonB-dependent receptor (HphR), which is important for survival and/or dissemination into the vasculature in a mouse model of pulmonary infection. Our results indicate that A. baumannii uses a two-component receptor system for the acquisition of heme from host heme reservoirs.
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Affiliation(s)
- Thomas J Bateman
- Department of Biochemistry, University of Toronto, Toronto, ON, Canada
| | - Megha Shah
- Department of Biochemistry, University of Toronto, Toronto, ON, Canada
| | - Timothy Pham Ho
- Department of Biochemistry, University of Toronto, Toronto, ON, Canada
| | | | - Chuxi Pan
- Department of Biochemistry, University of Toronto, Toronto, ON, Canada
| | - Greg Harris
- National Research Council Canada, Human Health Therapeutics (HHT) Research Center, Ottawa, ON, Canada
| | - Jamie E Fegan
- Department of Molecular Genetics, University of Toronto, Toronto, ON, Canada
| | - Epshita A Islam
- Department of Biochemistry, University of Toronto, Toronto, ON, Canada
| | - Sang Kyun Ahn
- Department of Molecular Genetics, University of Toronto, Toronto, ON, Canada
| | - Yogesh Hooda
- Department of Biochemistry, University of Toronto, Toronto, ON, Canada
| | - Scott D Gray-Owen
- Department of Molecular Genetics, University of Toronto, Toronto, ON, Canada
| | - Wangxue Chen
- National Research Council Canada, Human Health Therapeutics (HHT) Research Center, Ottawa, ON, Canada
| | - Trevor F Moraes
- Department of Biochemistry, University of Toronto, Toronto, ON, Canada.
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10
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Conde-Pérez K, Vázquez-Ucha JC, Álvarez-Fraga L, Ageitos L, Rumbo-Feal S, Martínez-Guitián M, Trigo-Tasende N, Rodríguez J, Bou G, Jiménez C, Beceiro A, Poza M. In-Depth Analysis of the Role of the Acinetobactin Cluster in the Virulence of Acinetobacter baumannii. Front Microbiol 2021; 12:752070. [PMID: 34675911 PMCID: PMC8524058 DOI: 10.3389/fmicb.2021.752070] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2021] [Accepted: 09/16/2021] [Indexed: 11/13/2022] Open
Abstract
Acinetobacter baumannii is a multidrug-resistant pathogen that represents a serious threat to global health. A. baumannii possesses a wide range of virulence factors that contribute to the bacterial pathogenicity. Among them, the siderophore acinetobactin is one of the most important, being essential for the development of the infection. In this study we performed an in-depth analysis of the acinetobactin cluster in the strain A. baumannii ATCC 17978. For this purpose, nineteen individual isogenic mutant strains were generated, and further phenotypical analysis were performed. Individual mutants lacking the biosynthetic genes entA, basG, basC, basD, and basB showed a significant loss in virulence, due to the disruption in the acinetobactin production. Similarly, the gene bauA, coding for the acinetobactin receptor, was also found to be crucial for the bacterial pathogenesis. In addition, the analysis of the ΔbasJ/ΔfbsB double mutant strain demonstrated the high level of genetic redundancy between siderophores where the role of specific genes of the acinetobactin cluster can be fulfilled by their fimsbactin redundant genes. Overall, this study highlights the essential role of entA, basG, basC, basD, basB and bauA in the pathogenicity of A. baumannii and provides potential therapeutic targets for the design of new antivirulence agents against this microorganism.
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Affiliation(s)
- Kelly Conde-Pérez
- Servicio de Microbiología del Complejo Hospitalario Universitario de A Coruña (CHUAC), Instituto de Investigación Biomédica de A Coruña (INIBIC), A Coruña, Spain.,Microbiome and Health, Faculty of Science, University of A Coruña, A Coruña, Spain
| | - Juan C Vázquez-Ucha
- Servicio de Microbiología del Complejo Hospitalario Universitario de A Coruña (CHUAC), Instituto de Investigación Biomédica de A Coruña (INIBIC), A Coruña, Spain
| | - Laura Álvarez-Fraga
- Servicio de Microbiología del Complejo Hospitalario Universitario de A Coruña (CHUAC), Instituto de Investigación Biomédica de A Coruña (INIBIC), A Coruña, Spain.,School of Chemistry and Molecular Biosciences, University of Queensland, Brisbane, QLD, Australia
| | - Lucía Ageitos
- Centro de Investigaciones Científicas Avanzadas (CICA) y Departamento de Química, Facultad de Ciencias, Agrupación Estratégica CICA-INIBIC, Universidad de A Coruña, A Coruña, Spain
| | - Soraya Rumbo-Feal
- Servicio de Microbiología del Complejo Hospitalario Universitario de A Coruña (CHUAC), Instituto de Investigación Biomédica de A Coruña (INIBIC), A Coruña, Spain.,Microbiome and Health, Faculty of Science, University of A Coruña, A Coruña, Spain
| | - Marta Martínez-Guitián
- Servicio de Microbiología del Complejo Hospitalario Universitario de A Coruña (CHUAC), Instituto de Investigación Biomédica de A Coruña (INIBIC), A Coruña, Spain
| | - Noelia Trigo-Tasende
- Servicio de Microbiología del Complejo Hospitalario Universitario de A Coruña (CHUAC), Instituto de Investigación Biomédica de A Coruña (INIBIC), A Coruña, Spain
| | - Jaime Rodríguez
- Centro de Investigaciones Científicas Avanzadas (CICA) y Departamento de Química, Facultad de Ciencias, Agrupación Estratégica CICA-INIBIC, Universidad de A Coruña, A Coruña, Spain
| | - Germán Bou
- Servicio de Microbiología del Complejo Hospitalario Universitario de A Coruña (CHUAC), Instituto de Investigación Biomédica de A Coruña (INIBIC), A Coruña, Spain
| | - Carlos Jiménez
- Centro de Investigaciones Científicas Avanzadas (CICA) y Departamento de Química, Facultad de Ciencias, Agrupación Estratégica CICA-INIBIC, Universidad de A Coruña, A Coruña, Spain
| | - Alejandro Beceiro
- Servicio de Microbiología del Complejo Hospitalario Universitario de A Coruña (CHUAC), Instituto de Investigación Biomédica de A Coruña (INIBIC), A Coruña, Spain
| | - Margarita Poza
- Servicio de Microbiología del Complejo Hospitalario Universitario de A Coruña (CHUAC), Instituto de Investigación Biomédica de A Coruña (INIBIC), A Coruña, Spain.,Microbiome and Health, Faculty of Science, University of A Coruña, A Coruña, Spain
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11
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Kumar S, Anwer R, Azzi A. Virulence Potential and Treatment Options of Multidrug-Resistant (MDR) Acinetobacter baumannii. Microorganisms 2021; 9:microorganisms9102104. [PMID: 34683425 PMCID: PMC8541637 DOI: 10.3390/microorganisms9102104] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2021] [Revised: 09/18/2021] [Accepted: 09/21/2021] [Indexed: 12/12/2022] Open
Abstract
Acinetobacter baumannii is an opportunistic pathogen which is undoubtedly known for a high rate of morbidity and mortality in hospital-acquired infections. A. baumannii causes life-threatening infections, including; ventilator-associated pneumonia (VAP), meningitis, bacteremia, and wound and urinary tract infections (UTI). In 2017, the World Health Organization listed A. baumannii as a priority-1 pathogen. The prevalence of A. baumannii infections and outbreaks emphasizes the direct need for the use of effective therapeutic agents for treating such infections. Available antimicrobials, such as; carbapenems, tigecycline, and colistins have insufficient effectiveness due to the appearance of multidrug-resistant strains, accentuating the need for alternative and novel therapeutic remedies. To understand and overcome this menace, the knowledge of recent discoveries on the virulence factors of A. baumannii is needed. Herein, we summarized the role of various virulence factors, including; outer membrane proteins, efflux pumps, biofilm, penicillin-binding proteins, and siderophores/iron acquisition systems. We reviewed the recent scientific literature on different A. baumannii virulence factors and the effective antimicrobial agents for the treatment and management of bacterial infections.
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Affiliation(s)
- Sunil Kumar
- Department of Biotechnology, Maharishi Markandeshwar (Deemed to Be University), Mullana, Ambala 133207, India;
| | - Razique Anwer
- Department of Pathology, College of Medicine, Imam Mohammad Ibn Saud Islamic University (IMSIU), Riyadh 13317-4233, Saudi Arabia;
| | - Arezki Azzi
- Department of Biochemistry, College of Medicine, Imam Mohammad Ibn Saud Islamic University (IMSIU), Riyadh 13317-4233, Saudi Arabia
- Correspondence:
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12
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Pimentel C, Le C, Tuttobene MR, Subils T, Papp-Wallace KM, Bonomo RA, Tolmasky ME, Ramirez MS. Interaction of Acinetobacter baumannii with Human Serum Albumin: Does the Host Determine the Outcome? Antibiotics (Basel) 2021; 10:antibiotics10070833. [PMID: 34356754 PMCID: PMC8300715 DOI: 10.3390/antibiotics10070833] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2021] [Revised: 07/06/2021] [Accepted: 07/06/2021] [Indexed: 01/16/2023] Open
Abstract
Acinetobacter baumannii has become a serious threat to human health due to its extreme antibiotic resistance, environmental persistence, and capacity to survive within the host. Two A. baumannii strains, A118 and AB5075, commonly used as model systems, and three carbapenem-resistant strains, which are becoming ever more dangerous due to the multiple drugs they can resist, were exposed to 3.5% human serum albumin (HSA) and human serum (HS) to evaluate their response with respect to antimicrobial resistance, biofilm formation, and quorum sensing, all features responsible for increasing survival and persistence in the environment and human body. Expression levels of antibiotic resistance genes were modified differently when examined in different strains. The cmlA gene was upregulated or downregulated in conditions of exposure to 3.5% HSA or HS depending on the strain. Expression levels of pbp1 and pbp3 tended to be increased by the presence of HSA and HS, but the effect was not seen in all strains. A. baumannii A118 growing in the presence of HS did not experience increased expression of these genes. Aminoglycoside-modifying enzymes were also expressed at higher or lower levels in the presence of HSA or HS. Still, the response was not uniform; in some cases, expression was enhanced, and in other cases, it was tapered. While A. baumannii AB5075 became more susceptible to rifampicin in the presence of 3.5% HSA or HS, strain A118 did not show any changes. Expression of arr2, a gene involved in resistance to rifampicin present in A. baumannii AMA16, was expressed at higher levels when HS was present in the culture medium. HSA and HS reduced biofilm formation and production of N-Acyl Homoserine Lactone, a compound intimately associated with quorum sensing. In conclusion, HSA, the main component of HS, stimulates a variety of adaptative responses in infecting A. baumannii strains.
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Affiliation(s)
- Camila Pimentel
- Center for Applied Biotechnology Studies, Department of Biological Science, College of Natural Sciences and Mathematics, California State University Fullerton, Fullerton, CA 92831-3599, USA; (C.P.); (C.L.); (M.E.T.)
| | - Casin Le
- Center for Applied Biotechnology Studies, Department of Biological Science, College of Natural Sciences and Mathematics, California State University Fullerton, Fullerton, CA 92831-3599, USA; (C.P.); (C.L.); (M.E.T.)
| | - Marisel R. Tuttobene
- Área Biología Molecular, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Rosario 2000, Argentina;
| | - Tomas Subils
- Instituto de Procesos Biotecnológicos y Químicos de Rosario (IPROBYQ, CONICET-UNR), Rosario S2002LRK, Argentina;
| | - Krisztina M. Papp-Wallace
- Research Service and GRECC, Louis Stokes Cleveland Department of Veterans Affairs Medical Center, Cleveland, OH 44106, USA; (K.M.P.-W.); (R.A.B.)
- Departments of Medicine, Pharmacology, Molecular Biology and Microbiology, Biochemistry, Proteomics and Bioinformatics, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA
- CWRU-Cleveland VAMC Center for Antimicrobial Resistance and Epidemiology (Case VA CARES), Cleveland, OH 44106, USA
| | - Robert A. Bonomo
- Research Service and GRECC, Louis Stokes Cleveland Department of Veterans Affairs Medical Center, Cleveland, OH 44106, USA; (K.M.P.-W.); (R.A.B.)
- Departments of Medicine, Pharmacology, Molecular Biology and Microbiology, Biochemistry, Proteomics and Bioinformatics, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA
- CWRU-Cleveland VAMC Center for Antimicrobial Resistance and Epidemiology (Case VA CARES), Cleveland, OH 44106, USA
| | - Marcelo E. Tolmasky
- Center for Applied Biotechnology Studies, Department of Biological Science, College of Natural Sciences and Mathematics, California State University Fullerton, Fullerton, CA 92831-3599, USA; (C.P.); (C.L.); (M.E.T.)
| | - Maria Soledad Ramirez
- Center for Applied Biotechnology Studies, Department of Biological Science, College of Natural Sciences and Mathematics, California State University Fullerton, Fullerton, CA 92831-3599, USA; (C.P.); (C.L.); (M.E.T.)
- Correspondence: ; Tel.: +1-657-278-4562
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Klebba PE, Newton SMC, Six DA, Kumar A, Yang T, Nairn BL, Munger C, Chakravorty S. Iron Acquisition Systems of Gram-negative Bacterial Pathogens Define TonB-Dependent Pathways to Novel Antibiotics. Chem Rev 2021; 121:5193-5239. [PMID: 33724814 PMCID: PMC8687107 DOI: 10.1021/acs.chemrev.0c01005] [Citation(s) in RCA: 50] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Iron is an indispensable metabolic cofactor in both pro- and eukaryotes, which engenders a natural competition for the metal between bacterial pathogens and their human or animal hosts. Bacteria secrete siderophores that extract Fe3+ from tissues, fluids, cells, and proteins; the ligand gated porins of the Gram-negative bacterial outer membrane actively acquire the resulting ferric siderophores, as well as other iron-containing molecules like heme. Conversely, eukaryotic hosts combat bacterial iron scavenging by sequestering Fe3+ in binding proteins and ferritin. The variety of iron uptake systems in Gram-negative bacterial pathogens illustrates a range of chemical and biochemical mechanisms that facilitate microbial pathogenesis. This document attempts to summarize and understand these processes, to guide discovery of immunological or chemical interventions that may thwart infectious disease.
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Affiliation(s)
- Phillip E Klebba
- Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, Kansas 66506, United States
| | - Salete M C Newton
- Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, Kansas 66506, United States
| | - David A Six
- Venatorx Pharmaceuticals, Inc., 30 Spring Mill Drive, Malvern, Pennsylvania 19355, United States
| | - Ashish Kumar
- Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, Kansas 66506, United States
| | - Taihao Yang
- Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, Kansas 66506, United States
| | - Brittany L Nairn
- Department of Biological Sciences, Bethel University, 3900 Bethel Drive, St. Paul, Minnesota 55112, United States
| | - Colton Munger
- Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, Kansas 66506, United States
| | - Somnath Chakravorty
- Jacobs School of Medicine and Biomedical Sciences, SUNY Buffalo, Buffalo, New York 14203, United States
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14
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Gene knockout revealed the role of gene feoA in cell growth and division of Lactobacillus delbrueckii subsp. bulgaricus. Arch Microbiol 2021; 203:3541-3549. [PMID: 33942158 DOI: 10.1007/s00203-021-02345-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2020] [Revised: 04/17/2021] [Accepted: 04/21/2021] [Indexed: 10/21/2022]
Abstract
Gene feoA plays an important role in cell growth because of its function of transport Fe2+ which is a necessary element for cells. In this study, the recombinant plasmid pUC19-feoA-Tet was successfully constructed using the inserted gene inactivation method. Using the homologous recombination technique, the tet gene was used as a resistance screening marker to knock out the feoA gene of Lactobacillus delbrueckii subsp. bulgaricus 34.5 (strain 34.5). Comparative analysis of growth curves revealed the growth changes in the absence of feoA gene in strain 34.5. The results showed that the growth of the bacteria was prolonged by 2 h and could be restored in the stationary phase. To further study whether feoA is related to the cell division of strain 34.5, the qPCR experiment was carried out. The results showed that, compared with the wild-type strain, the expression of genes related to cell division in the mutant strain was up-regulated in the pre-log phase, down-regulated in the late-log phase, and returned to the original level in the stationary phase. These findings provide ideas for Lactobacillus delbrueckii subsp. bulgaricus to control division and cell cycle.
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Martínez-Guitián M, Vázquez-Ucha JC, Álvarez-Fraga L, Conde-Pérez K, Bou G, Poza M, Beceiro A. Antisense inhibition of lpxB gene expression in Acinetobacter baumannii by peptide-PNA conjugates and synergy with colistin. J Antimicrob Chemother 2021; 75:51-59. [PMID: 31586411 DOI: 10.1093/jac/dkz409] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2019] [Revised: 08/28/2019] [Accepted: 09/03/2019] [Indexed: 12/12/2022] Open
Abstract
BACKGROUND LpxB is an enzyme involved in the biosynthesis pathway of lipid A, a component of LPS. OBJECTIVES To evaluate the lpxB gene in Acinetobacter baumannii as a potential therapeutic target and to propose antisense agents such as peptide nucleic acids (PNAs) as a tool to combat bacterial infection, either alone or in combination with known antimicrobial therapies. METHODS RNA-seq analysis of the A. baumannii ATCC 17978 strain in a murine pneumonia model was performed to study the in vivo expression of lpxB. Protein expression was studied in the presence or absence of anti-lpxB (KFF)3K-PNA (pPNA). Time-kill curve analyses and protection assays of infected A549 cells were performed. The chequerboard technique was used to test for synergy between pPNA and colistin. A Galleria mellonella infection model was used to test the in vivo efficacy of pPNA. RESULTS The lpxB gene was overexpressed during pneumonia. Treatment with a specific pPNA inhibited LpxB expression in vitro, decreased survival of the ATCC 17978 strain and increased the survival rate of infected A549 cells. Synergy was observed between pPNA and colistin in colistin-susceptible strains. In vivo assays confirmed that a combination treatment of anti-lpxB pPNA and colistin was more effective than colistin in monotherapy. CONCLUSIONS The lpxB gene is essential for A. baumannii survival. Anti-lpxB pPNA inhibits LpxB expression, causing bacterial death. This pPNA showed synergy with colistin and increased the survival rate in G. mellonella. The data suggest that antisense pPNA molecules blocking the lpxB gene could be used as antibacterial agents.
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Affiliation(s)
- Marta Martínez-Guitián
- Servicio de Microbiología do Complexo Hospitalario Universitario da Coruña (CHUAC), Instituto de Investigación Biomédica da Coruña (INIBIC), Centro de Investigacións Científicas Avanzadas (CICA), Universidade da Coruña (UDC), A Coruña, Spain
| | - Juan Carlos Vázquez-Ucha
- Servicio de Microbiología do Complexo Hospitalario Universitario da Coruña (CHUAC), Instituto de Investigación Biomédica da Coruña (INIBIC), Centro de Investigacións Científicas Avanzadas (CICA), Universidade da Coruña (UDC), A Coruña, Spain
| | - Laura Álvarez-Fraga
- Servicio de Microbiología do Complexo Hospitalario Universitario da Coruña (CHUAC), Instituto de Investigación Biomédica da Coruña (INIBIC), Centro de Investigacións Científicas Avanzadas (CICA), Universidade da Coruña (UDC), A Coruña, Spain
| | - Kelly Conde-Pérez
- Servicio de Microbiología do Complexo Hospitalario Universitario da Coruña (CHUAC), Instituto de Investigación Biomédica da Coruña (INIBIC), Centro de Investigacións Científicas Avanzadas (CICA), Universidade da Coruña (UDC), A Coruña, Spain
| | - Germán Bou
- Servicio de Microbiología do Complexo Hospitalario Universitario da Coruña (CHUAC), Instituto de Investigación Biomédica da Coruña (INIBIC), Centro de Investigacións Científicas Avanzadas (CICA), Universidade da Coruña (UDC), A Coruña, Spain
| | - Margarita Poza
- Servicio de Microbiología do Complexo Hospitalario Universitario da Coruña (CHUAC), Instituto de Investigación Biomédica da Coruña (INIBIC), Centro de Investigacións Científicas Avanzadas (CICA), Universidade da Coruña (UDC), A Coruña, Spain
| | - Alejandro Beceiro
- Servicio de Microbiología do Complexo Hospitalario Universitario da Coruña (CHUAC), Instituto de Investigación Biomédica da Coruña (INIBIC), Centro de Investigacións Científicas Avanzadas (CICA), Universidade da Coruña (UDC), A Coruña, Spain
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16
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Mea HJ, Yong PVC, Wong EH. An overview of Acinetobacter baumannii pathogenesis: Motility, adherence and biofilm formation. Microbiol Res 2021; 247:126722. [PMID: 33618061 DOI: 10.1016/j.micres.2021.126722] [Citation(s) in RCA: 53] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2020] [Revised: 01/29/2021] [Accepted: 02/01/2021] [Indexed: 12/13/2022]
Abstract
The Gram-negative opportunistic pathogen Acinetobacter baumannii has gain notoriety in recent decades, primarily due to its propensity to cause nosocomial infections in critically ill patients. Its global spread, multi-drug resistance features and plethora of virulence factors make it a serious threat to public health worldwide. Though much effort has been expended in uncovering its successes, it continues to confound researchers due to its highly adaptive nature, mutating to meet the needs of a given environment. Its persistence in the clinical setting allows it to be in close proximity to a potential host, where contact can be made facilitating infection and colonization. In this article, we aim to provide a current overview of the bacterial virulence factors, specifically focusing on factors involved in the initial stages of infection, highlighting the role of adaptation facilitated by two-component systems and biofilm formation. Finally, the study of host-pathogen interactions using available animal models, their suitability, notable findings and some perspectives moving forward are also discussed.
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Affiliation(s)
- Hing Jian Mea
- School of Biosciences, Faculty of Health and Medical Sciences, Taylor's University Lakeside Campus, 47500, Subang Jaya, Selangor Darul Ehsan, Malaysia
| | - Phelim Voon Chen Yong
- School of Biosciences, Faculty of Health and Medical Sciences, Taylor's University Lakeside Campus, 47500, Subang Jaya, Selangor Darul Ehsan, Malaysia
| | - Eng Hwa Wong
- School of Medicine, Faculty of Health and Medical Sciences, Taylor's University Lakeside Campus, 47500, Subang Jaya, Selangor Darul Ehsan, Malaysia.
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17
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Sheldon JR, Skaar EP. Acinetobacter baumannii can use multiple siderophores for iron acquisition, but only acinetobactin is required for virulence. PLoS Pathog 2020; 16:e1008995. [PMID: 33075115 PMCID: PMC7595644 DOI: 10.1371/journal.ppat.1008995] [Citation(s) in RCA: 66] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2020] [Revised: 10/29/2020] [Accepted: 09/18/2020] [Indexed: 12/22/2022] Open
Abstract
Acinetobacter baumannii is an emerging pathogen that poses a global health threat due to a lack of therapeutic options for treating drug-resistant strains. In addition to acquiring resistance to last-resort antibiotics, the success of A. baumannii is partially due to its ability to effectively compete with the host for essential metals. Iron is fundamental in shaping host-pathogen interactions, where the host restricts availability of this nutrient in an effort to curtail bacterial proliferation. To circumvent restriction, pathogens possess numerous mechanisms to obtain iron, including through the use of iron-scavenging siderophores. A. baumannii elaborates up to ten distinct siderophores, encoded from three different loci: acinetobactin and pre-acinetobactin (collectively, acinetobactin), baumannoferrins A and B, and fimsbactins A-F. The expression of multiple siderophores is common amongst bacterial pathogens and often linked to virulence, yet the collective contribution of these siderophores to A. baumannii survival and pathogenesis has not been investigated. Here we begin dissecting functional redundancy in the siderophore-based iron acquisition pathways of A. baumannii. Excess iron inhibits overall siderophore production by the bacterium, and the siderophore-associated loci are uniformly upregulated during iron restriction in vitro and in vivo. Further, disrupting all of the siderophore biosynthetic pathways is necessary to drastically reduce total siderophore production by A. baumannii, together suggesting a high degree of functional redundancy between the metabolites. By contrast, inactivation of acinetobactin biosynthesis alone impairs growth on human serum, transferrin, and lactoferrin, and severely attenuates survival of A. baumannii in a murine bacteremia model. These results suggest that whilst A. baumannii synthesizes multiple iron chelators, acinetobactin is critical to supporting growth of the pathogen on host iron sources. Given the acinetobactin locus is highly conserved and required for virulence of A. baumannii, designing therapeutics targeting the biosynthesis and/or transport of this siderophore may represent an effective means of combating this pathogen.
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Affiliation(s)
- Jessica R. Sheldon
- Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
- Vanderbilt Institute for Infection, Immunology, and Inflammation, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
| | - Eric P. Skaar
- Department of Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
- Vanderbilt Institute for Infection, Immunology, and Inflammation, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
- Vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville, Tennessee, United States of America
- * E-mail:
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18
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Martínez-Guitián M, Vázquez-Ucha JC, Álvarez-Fraga L, Conde-Pérez K, Vallejo JA, Perina A, Bou G, Poza M, Beceiro A. Global Transcriptomic Analysis During Murine Pneumonia Infection Reveals New Virulence Factors in Acinetobacter baumannii. J Infect Dis 2020; 223:1356-1366. [DOI: 10.1093/infdis/jiaa522] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2020] [Accepted: 08/13/2020] [Indexed: 12/15/2022] Open
Abstract
Abstract
Background
Infections caused by multidrug-resistant pathogens such as Acinetobacter baumannii constitute a major health problem worldwide. In this study we present a global in vivo transcriptomic analysis of A. baumannii isolated from the lungs of mice with pneumonia infection.
Methods
Mice were infected with A. baumannii ATCC 17978 and AbH12O-A2 strains and the total bacterial RNA were analyzed by RNA sequencing. Lists of differentially expressed genes were obtained and 14 of them were selected for gene deletion and further analysis.
Results
Transcriptomic analysis revealed a specific gene expression profile in A. baumannii during lung infection with upregulation of genes involved in iron acquisition and host invasion. Mutant strains lacking feoA, mtnN, yfgC, basB, hisF, oatA, and bfnL showed a significant loss of virulence in murine pneumonia. A decrease in biofilm formation, adherence to human epithelial cells, and growth rate was observed in selected mutants.
Conclusions
This study provides an insight into A. baumannii gene expression profile during murine pneumonia infection. Data revealed that 7 in vivo upregulated genes were involved in virulence and could be considered new therapeutic targets.
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Affiliation(s)
- Marta Martínez-Guitián
- Servicio de Microbiología del Complejo Hospitalario Universitario, Instituto de Investigación Biomédica, Centro de Investigaciones Científicas Avanzadas, Universidad de A Coruña, A Coruña, Spain
| | - Juan C Vázquez-Ucha
- Servicio de Microbiología del Complejo Hospitalario Universitario, Instituto de Investigación Biomédica, Centro de Investigaciones Científicas Avanzadas, Universidad de A Coruña, A Coruña, Spain
| | - Laura Álvarez-Fraga
- Servicio de Microbiología del Complejo Hospitalario Universitario, Instituto de Investigación Biomédica, Centro de Investigaciones Científicas Avanzadas, Universidad de A Coruña, A Coruña, Spain
| | - Kelly Conde-Pérez
- Servicio de Microbiología del Complejo Hospitalario Universitario, Instituto de Investigación Biomédica, Centro de Investigaciones Científicas Avanzadas, Universidad de A Coruña, A Coruña, Spain
| | - Juan A Vallejo
- Servicio de Microbiología del Complejo Hospitalario Universitario, Instituto de Investigación Biomédica, Centro de Investigaciones Científicas Avanzadas, Universidad de A Coruña, A Coruña, Spain
| | | | - Germán Bou
- Servicio de Microbiología del Complejo Hospitalario Universitario, Instituto de Investigación Biomédica, Centro de Investigaciones Científicas Avanzadas, Universidad de A Coruña, A Coruña, Spain
| | - Margarita Poza
- Servicio de Microbiología del Complejo Hospitalario Universitario, Instituto de Investigación Biomédica, Centro de Investigaciones Científicas Avanzadas, Universidad de A Coruña, A Coruña, Spain
| | - Alejandro Beceiro
- Servicio de Microbiología del Complejo Hospitalario Universitario, Instituto de Investigación Biomédica, Centro de Investigaciones Científicas Avanzadas, Universidad de A Coruña, A Coruña, Spain
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Marine Organisms from the Yucatan Peninsula (Mexico) as a Potential Natural Source of Antibacterial Compounds. Mar Drugs 2020; 18:md18070369. [PMID: 32708418 PMCID: PMC7404059 DOI: 10.3390/md18070369] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2020] [Revised: 07/10/2020] [Accepted: 07/15/2020] [Indexed: 01/15/2023] Open
Abstract
A total of 51 sponges (Porifera) and 13 ascidians (Chordata) were collected on the coast of the Yucatan Peninsula (Mexico) and extracted with organic solvents. The resulting extracts were screened for antibacterial activity against four multidrug-resistant (MDR) bacterial pathogens: the Gram-negative Acinetobacter baumannii, Klebsiella pneumoniae, and Pseudomonas aeruginosa and the Gram-positive Staphylococcus aureus. The minimum inhibitory concentrations (MICs) of the organic extracts of each marine organism were determined using a broth microdilution assay. Extracts of eight of the species, in particular the Agelas citrina and Haliclona (Rhizoniera) curacaoensis, displayed activity against some of the pathogens tested. Some of the extracts showed similar MIC values to known antibiotics such as penicillins and aminoglycosides. This study is the first to carry out antimicrobial screening of extracts of marine sponges and ascidians collected from the Yucatan Peninsula. Bioassay-guided fractionation of the active extracts from the sponges Amphimedon compressa and A. citrina displayed, as a preliminary result, that an inseparable mixture of halitoxins and amphitoxins and (-)-agelasine B, respectively, are the major compounds responsible for their corresponding antibacterial activities. This is the first report of the antimicrobial activity of halitoxins and amphitoxins against major multidrug-resistant human pathogens. The promising antibacterial activities detected in this study indicate the coast of Yucatan Peninsula as a potential source of a great variety of marine organisms worthy of further research.
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Zhang Y, Sen S, Giedroc DP. Iron Acquisition by Bacterial Pathogens: Beyond Tris-Catecholate Complexes. Chembiochem 2020; 21:1955-1967. [PMID: 32180318 PMCID: PMC7367709 DOI: 10.1002/cbic.201900778] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2019] [Revised: 03/06/2020] [Indexed: 12/11/2022]
Abstract
Sequestration of the essential nutrient iron from bacterial invaders that colonize the vertebrate host is a central feature of nutritional immunity and the "fight over transition metals" at the host-pathogen interface. The iron quota for many bacterial pathogens is large, as iron enzymes often make up a significant share of the metalloproteome. Iron enzymes play critical roles in respiration, energy metabolism, and other cellular processes by catalyzing a wide range of oxidation-reduction, electron transfer, and oxygen activation reactions. In this Concept article, we discuss recent insights into the diverse ways that bacterial pathogens acquire this essential nutrient, beyond the well-characterized tris-catecholate FeIII complexes, in competition and cooperation with significant host efforts to cripple these processes. We also discuss pathogen strategies to adapt their metabolism to less-than-optimal iron concentrations, and briefly speculate on what might be an integrated adaptive response to the concurrent limitation of both iron and zinc in the infected host.
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Affiliation(s)
- Yifan Zhang
- Department of Chemistry, Indiana University, Bloomington, IN 47405-7102, USA
- Department of Molecular and Cellular Biochemistry, Indiana University, Bloomington, IN 47405-7102, USA
| | - Sambuddha Sen
- Department of Chemistry, Indiana University, Bloomington, IN 47405-7102, USA
| | - David P Giedroc
- Department of Chemistry, Indiana University, Bloomington, IN 47405-7102, USA
- Department of Molecular and Cellular Biochemistry, Indiana University, Bloomington, IN 47405-7102, USA
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Kpi, a chaperone-usher pili system associated with the worldwide-disseminated high-risk clone Klebsiella pneumoniae ST-15. Proc Natl Acad Sci U S A 2020; 117:17249-17259. [PMID: 32641516 PMCID: PMC7382220 DOI: 10.1073/pnas.1921393117] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Control of infections caused by carbapenem-resistant Klebsiella pneumoniae continues to be challenging. The success of this pathogen is favored by its ability to acquire antimicrobial resistance and to spread and persist in both the environment and in humans. The emergence of clinically important clones, such as sequence types 11, 15, 101, and 258, has been reported worldwide. However, the mechanisms promoting the dissemination of such high-risk clones are unknown. Unraveling the factors that play a role in the pathobiology and epidemicity of K. pneumoniae is therefore important for managing infections. To address this issue, we studied a carbapenem-resistant ST-15 K. pneumoniae isolate (Kp3380) that displayed a remarkable adherent phenotype with abundant pilus-like structures. Genome sequencing enabled us to identify a chaperone-usher pili system (Kpi) in Kp3380. Analysis of a large K. pneumoniae population from 32 European countries showed that the Kpi system is associated with the ST-15 clone. Phylogenetic analysis of the operon revealed that Kpi belongs to the little-characterized γ2-fimbrial clade. We demonstrate that Kpi contributes positively to the ability of K. pneumoniae to form biofilms and adhere to different host tissues. Moreover, the in vivo intestinal colonizing capacity of the Kpi-defective mutant was significantly reduced, as was its ability to infect Galleria mellonella The findings provide information about the pathobiology and epidemicity of Kpi+ K. pneumoniae and indicate that the presence of Kpi may explain the success of the ST-15 clone. Disrupting bacterial adherence to the intestinal surface could potentially target gastrointestinal colonization.
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Ramirez MS, Bonomo RA, Tolmasky ME. Carbapenemases: Transforming Acinetobacter baumannii into a Yet More Dangerous Menace. Biomolecules 2020; 10:biom10050720. [PMID: 32384624 PMCID: PMC7277208 DOI: 10.3390/biom10050720] [Citation(s) in RCA: 113] [Impact Index Per Article: 28.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2020] [Revised: 04/27/2020] [Accepted: 04/29/2020] [Indexed: 02/07/2023] Open
Abstract
Acinetobacter baumannii is a common cause of serious nosocomial infections. Although community-acquired infections are observed, the vast majority occur in people with preexisting comorbidities. A. baumannii emerged as a problematic pathogen in the 1980s when an increase in virulence, difficulty in treatment due to drug resistance, and opportunities for infection turned it into one of the most important threats to human health. Some of the clinical manifestations of A. baumannii nosocomial infection are pneumonia; bloodstream infections; lower respiratory tract, urinary tract, and wound infections; burn infections; skin and soft tissue infections (including necrotizing fasciitis); meningitis; osteomyelitis; and endocarditis. A. baumannii has an extraordinary genetic plasticity that results in a high capacity to acquire antimicrobial resistance traits. In particular, acquisition of resistance to carbapenems, which are among the antimicrobials of last resort for treatment of multidrug infections, is increasing among A. baumannii strains compounding the problem of nosocomial infections caused by this pathogen. It is not uncommon to find multidrug-resistant (MDR, resistance to at least three classes of antimicrobials), extensively drug-resistant (XDR, MDR plus resistance to carbapenems), and pan-drug-resistant (PDR, XDR plus resistance to polymyxins) nosocomial isolates that are hard to treat with the currently available drugs. In this article we review the acquired resistance to carbapenems by A. baumannii. We describe the enzymes within the OXA, NDM, VIM, IMP, and KPC groups of carbapenemases and the coding genes found in A. baumannii clinical isolates.
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Affiliation(s)
- Maria Soledad Ramirez
- Center for Applied Biotechnology Studies, Department of Biological Science, California State University Fullerton, Fullerton, CA 92831, USA;
| | - Robert A. Bonomo
- Medical Service and GRECC, Louis Stokes Cleveland Department of Veterans Affairs Medical Center, Cleveland, OH 44106, USA;
- Departments of Medicine, Pharmacology, Molecular Biology and Microbiology, Biochemistry, Proteomics and Bioinformatics; Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA
- WRU-Cleveland VAMC Center for Antimicrobial Resistance and Epidemiology (Case VA CARES), Cleveland, OH 44106, USA
| | - Marcelo E. Tolmasky
- Center for Applied Biotechnology Studies, Department of Biological Science, California State University Fullerton, Fullerton, CA 92831, USA;
- Correspondence: ; Tel.: +657-278-5263
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Orihuela CJ, Maus UA, Brown JS. Can animal models really teach us anything about pneumonia? Pro. Eur Respir J 2020; 55:55/1/1901539. [DOI: 10.1183/13993003.01539-2019] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2019] [Accepted: 10/03/2019] [Indexed: 01/03/2023]
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Therapeutic Efficacy of LN-1-255 in Combination with Imipenem in Severe Infection Caused by Carbapenem-Resistant Acinetobacter baumannii. Antimicrob Agents Chemother 2019; 63:AAC.01092-19. [PMID: 31383666 DOI: 10.1128/aac.01092-19] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2019] [Accepted: 07/23/2019] [Indexed: 11/20/2022] Open
Abstract
The carbapenem-hydrolyzing class D β-lactamases (CHDLs) are the main mechanism of carbapenem resistance in Acinetobacter baumannii CHDLs are not effectively inactivated by clinically available β-lactam-type inhibitors. We have previously described the in vitro efficacy of the inhibitor LN-1-255 in combination with carbapenems. The aim of this study was to compare the efficacy of LN-1-255 with that of imipenem in murine pneumonia using A. baumannii strains carrying their most extended carbapenemases, OXA-23 and OXA-24/40. The bla OXA-23 and bla OXA-24/40 genes were cloned into the carbapenem-susceptible A. baumannii ATCC 17978 strain. Clinical isolates Ab1 and JC12/04, producing the enzymes OXA-23 and OXA-24/40, respectively, were used in the study. Pharmacokinetic (PK) parameters were determined. An experimental pneumonia model was used to evaluate the efficacy of the combined imipenem-LN-1-255 therapy. MICs of imipenem decreased between 32- and 128-fold in the presence of LN-1-255. Intramuscular treatment with imipenem-LN-1-255 (30/50 mg/kg) decreased the bacterial burden by (i) 4 and 1.7 log10 CFU/g lung in the infection with the ATCC 17978-OXA-23 and Ab1 strains, respectively, and by (ii) 2.5 and 4.5 log10 CFU/g lung in the infection produced by the ATCC 17978-OXA-24/40 and the JC12/04 strains, respectively. In all assays, combined therapy offered higher protection against pneumonia than that provided by monotherapy. No toxicity was observed in treated mice. Imipenem treatment combined with LN-1-255 treatment significantly reduced the severity of infection by carbapenem-resistant A. baumannii strains carrying CHDLs. Preclinical assays demonstrated the potential of LN-1-255 and imipenem therapy as a new antibacterial treatment.
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Martínez-Guitián M, Vázquez-Ucha JC, Álvarez-Fraga L, Conde-Pérez K, Lasarte-Monterrubio C, Vallejo JA, Bou G, Poza M, Beceiro A. Involvement of HisF in the Persistence of Acinetobacter baumannii During a Pneumonia Infection. Front Cell Infect Microbiol 2019; 9:310. [PMID: 31555607 PMCID: PMC6727670 DOI: 10.3389/fcimb.2019.00310] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2019] [Accepted: 08/15/2019] [Indexed: 01/05/2023] Open
Abstract
Acinetobacter baumannii is currently considered one of the most problematic nosocomial microorganisms. In the present work the hisF gene from the ATCC 17978 strain and the AbH12O-A2 clinical isolate of A. baumannii was found over-expressed during the course of murine pneumonia infections. The study demonstrated that the A. baumannii ATCC 17978 mutant strain lacking the hisF gene induces a sub-lethal pneumonia infection in mice, while the complemented mutant strain increased its virulence. This histidine auxotroph mutant showed an increase on IL-6 secretion and leukocytes recruitment during infections. Furthermore, data revealed that the hisF gene, implicated in the innate immunity and inflammation, is involved in virulence during a pneumonia infection, which may partly explain the ability of this strain to persist in the lung. We suggest that HisF, essential for full virulence in this pathogen, should be considered a potential target for developing new antimicrobial therapies against A. baumannii. Importance Nosocomial pathogens such as A. baumannii are able to acquire and develop multi-drug resistance and represent an important clinical and economic problem. There is therefore an urgent need to find new therapeutic targets to fight against A. baumannii. In the present work, the potential of HisF from A. baumannii as a therapeutic target has been addressed since this protein is involved in the innate inmunity and the inflamatory response and seems essential to develop a pneumonia in mice. This work lays the groundwork for designing antimicrobial therapies that block the activity of HisF.
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Affiliation(s)
- Marta Martínez-Guitián
- Servicio de Microbiología Do Complexo Hospitalario Universitario da Coruña (CHUAC), Instituto de Investigación Biomédica da Coruña (INIBIC), Universidade da Coruña (UDC), A Coruña, Spain
| | - Juan C Vázquez-Ucha
- Servicio de Microbiología Do Complexo Hospitalario Universitario da Coruña (CHUAC), Instituto de Investigación Biomédica da Coruña (INIBIC), Universidade da Coruña (UDC), A Coruña, Spain
| | - Laura Álvarez-Fraga
- Servicio de Microbiología Do Complexo Hospitalario Universitario da Coruña (CHUAC), Instituto de Investigación Biomédica da Coruña (INIBIC), Universidade da Coruña (UDC), A Coruña, Spain
| | - Kelly Conde-Pérez
- Servicio de Microbiología Do Complexo Hospitalario Universitario da Coruña (CHUAC), Instituto de Investigación Biomédica da Coruña (INIBIC), Universidade da Coruña (UDC), A Coruña, Spain
| | - Cristina Lasarte-Monterrubio
- Servicio de Microbiología Do Complexo Hospitalario Universitario da Coruña (CHUAC), Instituto de Investigación Biomédica da Coruña (INIBIC), Universidade da Coruña (UDC), A Coruña, Spain
| | - Juan Andrés Vallejo
- Servicio de Microbiología Do Complexo Hospitalario Universitario da Coruña (CHUAC), Instituto de Investigación Biomédica da Coruña (INIBIC), Universidade da Coruña (UDC), A Coruña, Spain
| | - Germán Bou
- Servicio de Microbiología Do Complexo Hospitalario Universitario da Coruña (CHUAC), Instituto de Investigación Biomédica da Coruña (INIBIC), Universidade da Coruña (UDC), A Coruña, Spain
| | - Margarita Poza
- Servicio de Microbiología Do Complexo Hospitalario Universitario da Coruña (CHUAC), Instituto de Investigación Biomédica da Coruña (INIBIC), Universidade da Coruña (UDC), A Coruña, Spain
| | - Alejandro Beceiro
- Servicio de Microbiología Do Complexo Hospitalario Universitario da Coruña (CHUAC), Instituto de Investigación Biomédica da Coruña (INIBIC), Universidade da Coruña (UDC), A Coruña, Spain
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Morris FC, Dexter C, Kostoulias X, Uddin MI, Peleg AY. The Mechanisms of Disease Caused by Acinetobacter baumannii. Front Microbiol 2019; 10:1601. [PMID: 31379771 PMCID: PMC6650576 DOI: 10.3389/fmicb.2019.01601] [Citation(s) in RCA: 155] [Impact Index Per Article: 31.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2019] [Accepted: 06/26/2019] [Indexed: 01/29/2023] Open
Abstract
Acinetobacter baumannii is a Gram negative opportunistic pathogen that has demonstrated a significant insurgence in the prevalence of infections over recent decades. With only a limited number of “traditional” virulence factors, the mechanisms underlying the success of this pathogen remain of great interest. Major advances have been made in the tools, reagents, and models to study A. baumannii pathogenesis, and this has resulted in a substantial increase in knowledge. This article provides a comprehensive review of the bacterial virulence factors, the host immune responses, and animal models applicable for the study of this important human pathogen. Collating the most recent evidence characterizing bacterial virulence factors, their cellular targets and genetic regulation, we have encompassed numerous aspects important to the success of this pathogen, including membrane proteins and cell surface adaptations promoting immune evasion, mechanisms for nutrient acquisition and community interactions. The role of innate and adaptive immune responses is reviewed and areas of paucity in our understanding are highlighted. Finally, with the vast expansion of available animal models over recent years, we have evaluated those suitable for use in the study of Acinetobacter disease, discussing their advantages and limitations.
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Affiliation(s)
- Faye C Morris
- Infection and Immunity Program, Department of Microbiology, Monash Biomedicine Discovery Institute, Monash University, Clayton, VIC, Australia
| | - Carina Dexter
- Infection and Immunity Program, Department of Microbiology, Monash Biomedicine Discovery Institute, Monash University, Clayton, VIC, Australia
| | - Xenia Kostoulias
- Infection and Immunity Program, Department of Microbiology, Monash Biomedicine Discovery Institute, Monash University, Clayton, VIC, Australia
| | - Muhammad Ikhtear Uddin
- Infection and Immunity Program, Department of Microbiology, Monash Biomedicine Discovery Institute, Monash University, Clayton, VIC, Australia
| | - Anton Y Peleg
- Infection and Immunity Program, Department of Microbiology, Monash Biomedicine Discovery Institute, Monash University, Clayton, VIC, Australia.,Department of Infectious Diseases, The Alfred Hospital and Central Clinical School, Monash University, Melbourne, VIC, Australia
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Linkous RO, Sestok AE, Smith AT. The crystal structure of Klebsiella pneumoniae FeoA reveals a site for protein-protein interactions. Proteins 2019; 87:897-903. [PMID: 31162843 DOI: 10.1002/prot.25755] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2019] [Revised: 05/25/2019] [Accepted: 05/30/2019] [Indexed: 12/27/2022]
Abstract
In order to establish infection, pathogenic bacteria must obtain essential nutrients such as iron. Under acidic and/or anaerobic conditions, most bacteria utilize the Feo system in order to acquire ferrous iron (Fe2+ ) from their host environment. The mechanism of this process, including its regulation, remains poorly understood. In this work, we have determined the crystal structure of FeoA from the nosocomial agent Klebsiella pneumoniae (KpFeoA). Our structure reveals an SH3-like domain that mediates interactions between neighboring polypeptides via hydrophobic intercalations into a Leu-rich surface ridge. Using docking of a small peptide corresponding to a postulated FeoB partner binding site, we demonstrate that KpFeoA can assume both "open" and "closed" conformations, controlled by binding at this Leu-rich ridge. We propose a model in which a "C-shaped" clamp along the FeoA surface mediates interactions with its partner protein, FeoB. These findings are the first to demonstrate atomic-level details of FeoA-based protein-protein interactions and provide a framework for testing FeoA-FeoB interactions, which could be exploited for future antibiotic developments.
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Affiliation(s)
- Richard O Linkous
- Department of Chemistry and Biochemistry, University of Maryland, Baltimore, Maryland
| | - Alexandrea E Sestok
- Department of Chemistry and Biochemistry, University of Maryland, Baltimore, Maryland
| | - Aaron T Smith
- Department of Chemistry and Biochemistry, University of Maryland, Baltimore, Maryland
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Bohac TJ, Fang L, Giblin DE, Wencewicz TA. Fimsbactin and Acinetobactin Compete for the Periplasmic Siderophore Binding Protein BauB in Pathogenic Acinetobacter baumannii. ACS Chem Biol 2019; 14:674-687. [PMID: 30785725 DOI: 10.1021/acschembio.8b01051] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Environmental and pathogenic microbes produce siderophores as small iron-binding molecules to scavenge iron from natural environments. It is common for microbes to produce multiple siderophores to gain a competitive edge in mixed microbial environments. Strains of human pathogenic Acinetobacter baumannii produce up to three siderophores: acinetobactin, baumannoferrin, and fimsbactin. Production of acinetobactin and baumannoferrin is highly conserved among clinical isolates while fimsbactin production appears to be less common. Fimsbactin is structurally related to acinetobactin through the presence of catecholate and phenolate oxazoline metal-binding motifs, and both are derived from nonribosomal peptide assembly lines with similar catalytic domain orientations and identities. Here we report on the chemical, biochemical, and microbiological investigation of fimsbactin and acinetobactin alone and in combination. We show that fimsbactin forms a 1:1 complex with iron(III) that is thermodynamically more stable than the 2:1 acinetobactin ferric complex. Alone, both acinetobactin and fimsbactin stimulate A. baumannii growth, but in combination the two siderophores appear to compete and collectively inhibit bacterial growth. We show that fimsbactin directly competes with acinetobactin for binding the periplasmic siderophore-binding protein BauB suggesting a possible biochemical mechanism for the phenomenon where the buildup of apo-siderophores in the periplasm leads to iron starvation. We propose an updated model for siderophore utilization and competition in A. baumannii that frames the molecular, biochemical, and cellular interplay of multiple iron acquisition systems in a multidrug resistant Gram-negative human pathogen.
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Affiliation(s)
- Tabbetha J. Bohac
- Department of Chemistry, Washington University in St. Louis, One Brookings Drive, St. Louis, Missouri 63130, United States
| | - Luting Fang
- Department of Chemistry, Washington University in St. Louis, One Brookings Drive, St. Louis, Missouri 63130, United States
| | - Daryl E. Giblin
- Department of Chemistry, Washington University in St. Louis, One Brookings Drive, St. Louis, Missouri 63130, United States
| | - Timothy A. Wencewicz
- Department of Chemistry, Washington University in St. Louis, One Brookings Drive, St. Louis, Missouri 63130, United States
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Sestok AE, Linkous RO, Smith AT. Toward a mechanistic understanding of Feo-mediated ferrous iron uptake. Metallomics 2018; 10:887-898. [PMID: 29953152 PMCID: PMC6051883 DOI: 10.1039/c8mt00097b] [Citation(s) in RCA: 53] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Virtually all organisms require iron and have evolved to obtain this element in free or chelated forms. Under anaerobic or low pH conditions commonly encountered by numerous pathogens, iron predominantly exists in the ferrous (Fe2+) form. The ferrous iron transport (Feo) system is the only widespread mechanism dedicated solely to bacterial ferrous iron import, and this system has been linked to pathogenic virulence, bacterial colonization, and microbial survival. The canonical feo operon encodes for three proteins that comprise the Feo system: FeoA, a small cytoplasmic β-barrel protein; FeoB, a large, polytopic membrane protein with a soluble G-protein domain capable of hydrolyzing GTP; and FeoC, a small, cytoplasmic protein containing a winged-helix motif. While previous studies have revealed insight into soluble and fragmentary domains of the Feo system, the chief membrane-bound component FeoB remains poorly studied. However, recent advances have demonstrated that large quantities of intact FeoB can be overexpressed, purified, and biophysically characterized, revealing glimpses into FeoB function. Two models of full-length FeoB have been published, providing starting points for hypothesis-driven investigations into the mechanism of FeoB-mediated ferrous iron transport. Finally, in vivo studies have begun to shed light on how this system functions as a unique multicomponent complex. In light of these new data, this review will summarize what is known about the Feo system, including recent advancements in FeoB structure and function.
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Affiliation(s)
- Alexandrea E Sestok
- Department of Chemistry and Biochemistry, University of Maryland, Baltimore County, Baltimore, Maryland 21250, USA.
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