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Hajra D, Nair AV, Chakravortty D. An elegant nano-injection machinery for sabotaging the host: Role of Type III secretion system in virulence of different human and animal pathogenic bacteria. Phys Life Rev 2021; 38:25-54. [PMID: 34090822 DOI: 10.1016/j.plrev.2021.05.007] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2021] [Accepted: 05/23/2021] [Indexed: 01/22/2023]
Abstract
Various Gram-negative bacteria possess a specialized membrane-bound protein secretion system known as the Type III secretion system (T3SS), which transports the bacterial effector proteins into the host cytosol thereby helping in bacterial pathogenesis. The T3SS has a special needle-like translocon that can sense the contact with the host cell membrane and translocate effectors. The export apparatus of T3SS recognizes these effector proteins bound to chaperones and translocates them into the host cell. Once in the host cell cytoplasm, these effector proteins result in modulation of the host system and promote bacterial localization and infection. Using molecular biology, bioinformatics, genetic techniques, electron microscopic studies, and mathematical modeling, the structure and function of the T3SS and the corresponding effector proteins in various bacteria have been studied. The strategies used by different human pathogenic bacteria to modulate the host system and thereby enhance their virulence mechanism using T3SS have also been well studied. Here we review the history, evolution, and general structure of the T3SS, highlighting the details of its comparison with the flagellar export machinery. Also, this article provides mechanistic details about the common role of T3SS in subversion and manipulation of host cellular processes. Additionally, this review describes specific T3SS apparatus and the role of their specific effectors in bacterial pathogenesis by considering several human and animal pathogenic bacteria.
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Affiliation(s)
- Dipasree Hajra
- Department of Microbiology & Cell Biology, Indian Institute of Science, India
| | - Abhilash Vijay Nair
- Department of Microbiology & Cell Biology, Indian Institute of Science, India
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A comparative genomics approach identifies contact-dependent growth inhibition as a virulence determinant. Proc Natl Acad Sci U S A 2020; 117:6811-6821. [PMID: 32156726 DOI: 10.1073/pnas.1919198117] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Emerging evidence suggests the Pseudomonas aeruginosa accessory genome is enriched with uncharacterized virulence genes. Identification and characterization of such genes may reveal novel pathogenic mechanisms used by particularly virulent isolates. Here, we utilized a mouse bacteremia model to quantify the virulence of 100 individual P. aeruginosa bloodstream isolates and performed whole-genome sequencing to identify accessory genomic elements correlated with increased bacterial virulence. From this work, we identified a specific contact-dependent growth inhibition (CDI) system enriched among highly virulent P. aeruginosa isolates. CDI systems contain a large exoprotein (CdiA) with a C-terminal toxin (CT) domain that can vary between different isolates within a species. Prior work has revealed that delivery of a CdiA-CT domain upon direct cell-to-cell contact can inhibit replication of a susceptible target bacterium. Aside from mediating interbacterial competition, we observed our virulence-associated CdiA-CT domain to promote toxicity against mammalian cells in culture and lethality during mouse bacteremia. Structural and functional studies revealed this CdiA-CT domain to have in vitro tRNase activity, and mutations that abrogated this tRNAse activity in vitro also attenuated virulence. Furthermore, CdiA contributed to virulence in mice even in the absence of contact-dependent signaling. Overall, our findings indicate that this P. aeruginosa CDI system functions as both an interbacterial inhibition system and a bacterial virulence factor against a mammalian host. These findings provide an impetus for continued studies into the complex role of CDI systems in P. aeruginosa pathogenesis.
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Secretion of Flagellar Proteins by the Pseudomonas aeruginosa Type III Secretion-Injectisome System. J Bacteriol 2015; 197:2003-11. [PMID: 25845843 DOI: 10.1128/jb.00030-15] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2015] [Accepted: 03/30/2015] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED The opportunistic pathogen Pseudomonas aeruginosa utilizes an injectisome-type III secretion system (injectisome-T3SS) to elicit cytotoxicity toward epithelial cells and macrophages. Macrophage killing results from the cytotoxic properties of the translocated effector proteins (ExoS, ExoT, ExoU, and ExoY) and inflammasome-mediated induction of pyroptosis. Inflammasome activation can occur following Nlrc4-mediated recognition of cytosolic translocated flagellin (FliC). In the present study, we demonstrate that FliC is a secretion substrate of both the injectisome- and flagellum-associated T3SSs. Molecular analyses indicate that the first 20 amino-terminal residues of FliC are sufficient for secretion by the injectisome-T3SS and that the first 100 residues are sufficient for translocation of FliC into host cells. Although maximal inflammasome activation requires FliC, activation can also occur in the absence of FliC. This prompted us to examine whether other flagellar components might also be translocated into cells to elicit inflammasome activation. Indeed, we find that the flagellar cap (FliD), hook-associated (FlgK and FlgL), hook (FlgE), and rod (FlgE) proteins are secretion substrates of the injectisome-T3SS. None of these proteins, however, result in increased inflammasome activation when they are overexpressed in a fliC mutant and appear to be translocated into host cells. While a role in inflammasome activation has been excluded, these data raise the possibility that flagellar components, which are highly conserved between different bacterial species, trigger other specific host responses from the extracellular milieu or contribute to the pathogenesis of P. aeruginosa. IMPORTANCE The inflammasome is a host defense mechanism that recognizes invading bacteria and triggers an inflammatory immune response. The opportunistic pathogen P. aeruginosa produces both inflammasome agonists and antagonists. In this study, we demonstrate that overexpression of an agonist suppresses the activity of an antagonist, thereby resulting in inflammasome activation. Since the relative expression levels of agonists and antagonists likely vary between strains, these differences could be important predictors of whether a particular P. aeruginosa strain elicits inflammasome activation.
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Jain R, Kazmierczak BI. A conservative amino acid mutation in the master regulator FleQ renders Pseudomonas aeruginosa aflagellate. PLoS One 2014; 9:e97439. [PMID: 24827992 PMCID: PMC4020848 DOI: 10.1371/journal.pone.0097439] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2014] [Accepted: 04/17/2014] [Indexed: 11/21/2022] Open
Abstract
Flagellar-based motility plays a critical role in Pseudomonas aeruginosa pathogenesis, influencing both the establishment of bacterial infection and the host's response to the pathogen. Nonetheless, aflagellate clinical strains are often isolated from acutely and chronically infected patients and include the virulent laboratory strain PA103. We determined that PA103's aflagellate phenotype is the result of a single amino acid change (G240V) in the master flagellar regulator, FleQ. This mutation, which lies just outside the Walker B box of FleQ, abrogates the ability of FleQ to positively regulate flagellar gene expression. Reversal of this seemingly conservative amino acid substitution is sufficient to restore swimming motility to PA103, despite the presence of mutations in other flagellar genes of PA103. We also investigated the consequences of restoring flagellar assembly on PA103 virulence. Although a negative correlation between flagellar assembly and Type 3 secretion system (T3SS) expression has been reported previously, we did not observe downregulation of T3SS expression or function in Fla+ PA103. Restoration of flagellar assembly did, however, amplify IL-1 signals measured during murine pulmonary infection and was associated with increased bacterial clearance. These experiments suggest that loss of flagellar motility may primarily benefit PA103 by attenuating pathogen recognition and clearance during acute infection.
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Affiliation(s)
- Ruchi Jain
- Department of Internal Medicine (Infectious Diseases), Yale University School of Medicine, New Haven, Connecticut, United States of America
| | - Barbara I. Kazmierczak
- Department of Internal Medicine (Infectious Diseases), Yale University School of Medicine, New Haven, Connecticut, United States of America
- Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, Connecticut, United States of America
- * E-mail:
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Sullivan E, Bensman J, Lou M, Agnello M, Shriner K, Wong-Beringer A. Risk of developing pneumonia is enhanced by the combined traits of fluoroquinolone resistance and type III secretion virulence in respiratory isolates of Pseudomonas aeruginosa. Crit Care Med 2014; 42:48-56. [PMID: 23963124 DOI: 10.1097/ccm.0b013e318298a86f] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
OBJECTIVES To determine the differential association of host characteristics, antimicrobial resistance, and type III secretion system virulence of Pseudomonas aeruginosa isolates with respiratory syndromes in hospitalized adult patients. DESIGN Retrospective, cohort study. SETTING Community teaching hospital. PATIENTS Two hundred eighteen consecutive adult patients with respiratory culture positive for P. aeruginosa between January 2005 to January 2010. INTERVENTIONS Medical charts were reviewed to obtain demographic, laboratory, radiographic, and clinical information. Isolates were assayed by polymerase chain reaction for genes encoding the type III secretion system effectors (ExoU, ExoS, and PcrV) and for strain relatedness using randomly amplified polymorphic DNA analysis. Levofloxacin susceptibility was determined by broth microdilution. Patients were grouped by colonization, bronchitis, or pneumonia and were compared for differential risk of developing the clinical syndrome with respect to host and microbial characteristics. MEASUREMENTS AND MAIN RESULTS Half of the study cohort (54%, 117 of 218) had pneumonia, 32% (70 of 218) had bronchitis, and 14% (31 of 218) had colonization; in-hospital mortality was 35%, 11%, and 0%, respectively. Host factors strongly associated with pneumonia development were residence in long-term care facility, healthcare-associated acquisition of P. aeruginosa, higher Acute Physiology and Chronic Health Evaluation II score, presence of enteral feeding tube, mechanical ventilation, and recent history of pneumonia. Fluoroquinolone-resistant (57% vs 34%, 16%; p < 0.0001) and multidrug-resistant (36% vs 26%, 7%; p = 0.0045) strains were more likely to cause pneumonia than bronchitis or colonization, respectively. Analysis of host and microbial factors in a multivariate regression model yielded the combined traits of fluoroquinolone resistance and gene encoding the type III secretion system ExoU effector in P. aeruginosa as the single most significant predictor of pneumonia development. CONCLUSIONS These results suggest that fluoroquinolone-resistant phenotype in a type III secretion system exoU strain background contributes toward the pathogenesis of P. aeruginosa in pneumonia.
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Affiliation(s)
- Eva Sullivan
- 1Huntington Hospital, Pasadena, CA. 2University of Southern California, Los Angeles, CA
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Ledizet M, Murray TS, Puttagunta S, Slade MD, Quagliarello VJ, Kazmierczak BI. The ability of virulence factor expression by Pseudomonas aeruginosa to predict clinical disease in hospitalized patients. PLoS One 2012; 7:e49578. [PMID: 23152923 PMCID: PMC3495863 DOI: 10.1371/journal.pone.0049578] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2012] [Accepted: 10/10/2012] [Indexed: 12/30/2022] Open
Abstract
BACKGROUND Pseudomonas aeruginosa is an opportunistic pathogen that frequently causes hospital acquired colonization and infection. Accurate identification of host and bacterial factors associated with infection could aid treatment decisions for patients with P. aeruginosa cultured from clinical sites. METHODS We identified a prospective cohort of 248 hospitalized patients with positive P. aeruginosa cultures. Clinical data were analyzed to determine whether an individual met predefined criteria for infection versus colonization. P. aeruginosa isolates were tested for the expression of multiple phenotypes previously associated with virulence in animal models and humans. Logistic regression models were constructed to determine the degree of association between host and bacterial factors with P. aeruginosa infection of the bloodstream, lung, soft tissue and urinary tract. RESULTS One host factor (i.e. diabetes mellitus), and one bacterial factor, a Type 3 secretion system positive phenotype, were significantly associated with P. aeruginosa infection in our cohort. Subgroup analysis of patients with P. aeruginosa isolated from the urinary tract revealed that the presence of a urinary tract catheter or stent was an additional factor for P. aeruginosa infection. CONCLUSIONS Among hospitalized patients with culture-documented P. aeruginosa, infection is more likely to be present in those with diabetes mellitus and those harboring a Type 3 secretion positive bacterial strain.
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Affiliation(s)
- Michel Ledizet
- L2 Diagnostics, New Haven, Connecticut, United States of America
| | - Thomas S. Murray
- Department of Pediatrics (Infectious Diseases), Yale University School of Medicine, New Haven, Connecticut, United States of America
| | - Sailaja Puttagunta
- Department of Medicine, Sections of Infectious Diseases, Yale University School of Medicine, New Haven, Connecticut, United States of America
| | - Martin D. Slade
- Department of Occupational & Environmental Medicine, Yale University School of Medicine, New Haven, Connecticut, United States of America
| | - Vincent J. Quagliarello
- Department of Medicine, Sections of Infectious Diseases, Yale University School of Medicine, New Haven, Connecticut, United States of America
| | - Barbara I. Kazmierczak
- Department of Medicine, Sections of Infectious Diseases, Yale University School of Medicine, New Haven, Connecticut, United States of America
- Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, Connecticut, United States of America
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Hu H, Harmer C, Anuj S, Wainwright CE, Manos J, Cheney J, Harbour C, Zablotska I, Turnbull L, Whitchurch CB, Grimwood K, Rose B. Type 3 secretion system effector genotype and secretion phenotype of longitudinally collected Pseudomonas aeruginosa isolates from young children diagnosed with cystic fibrosis following newborn screening. Clin Microbiol Infect 2012; 19:266-72. [PMID: 22329595 DOI: 10.1111/j.1469-0691.2012.03770.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Studies of the type 3 secretion system (T3SS) in Pseudomonas aeruginosa isolates from chronically infected older children and adults with cystic fibrosis (CF) show a predominantly exoS+/exoU- (exoS+) genotype and loss of T3SS effector secretion over time. Relatively little is known about the role of the T3SS in the pathogenesis of early P. aeruginosa infection in the CF airway. In this longitudinal study, 168 P. aeruginosa isolates from 58 children diagnosed with CF following newborn screening and 47 isolates from homes of families with or without children with CF were genotyped by pulsed-field gel electrophoresis (PFGE) and T3SS genotype and phenotype determined using multiplex PCR and western blotting. Associations were sought between T3SS data and clinical variables and comparisons made between T3SS data of clinical and environmental PFGE genotypes. Seventy-seven of the 92 clinical strains were exoS+ (71% secretors (ExoS+)) and 15 were exoU+ (93% secretors (ExoU+)). Initial exoS+ strains were five times more likely to secrete ExoS than subsequent exoS+ strains at first isolation. The proportion of ExoS+ strains declined with increasing age at acquisition. No associations were found between T3SS characteristics and gender, site of isolation, exacerbation, a persistent strain or pulmonary outcomes. Fourteen of the 23 environmental strains were exoS+ (79% ExoS+) and nine were exoU+ (33% ExoU+). The exoU+ environmental strains were significantly less likely to secrete ExoU than clinical strains. This study provides new insight into the T3SS characteristics of P. aeruginosa isolated from the CF airway early in life.
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Affiliation(s)
- H Hu
- Department of Infectious Diseases and Immunology, Central Clinical School, University of Sydney, NSW 2006, Australia
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Cruz AC, Neves BC, Higa LYS, Folescu T, Marques EA, Milagres LG. Type III apparatus of Pseudomonas aeruginosa as a tool to diagnose pulmonary infection in cystic fibrosis patients. APMIS 2012; 120:622-7. [DOI: 10.1111/j.1600-0463.2012.02888.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2011] [Accepted: 01/10/2012] [Indexed: 11/30/2022]
Affiliation(s)
- Aline C. Cruz
- Department of Microbiology, Immunology and Parasitology; State University of Rio de Janeiro; Rio de Janeiro; RJ; Brazil
| | - Bianca C. Neves
- Department of Biochemistry; Institute of Chemistry; Federal University of Rio de Janeiro; Rio de Janeiro; RJ; Brazil
| | - Laurinda Y. S. Higa
- Department of Pulmonology; Fernandes Figueira Institute - FIOCRUZ; Rio de Janeiro; RJ; Brazil
| | - Tânia Folescu
- Department of Pulmonology; Fernandes Figueira Institute - FIOCRUZ; Rio de Janeiro; RJ; Brazil
| | - Elizabeth A. Marques
- Department of Microbiology, Immunology and Parasitology; State University of Rio de Janeiro; Rio de Janeiro; RJ; Brazil
| | - Lucimar G. Milagres
- Department of Microbiology, Immunology and Parasitology; State University of Rio de Janeiro; Rio de Janeiro; RJ; Brazil
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In vivo discrimination of type 3 secretion system-positive and -negative Pseudomonas aeruginosa via a caspase-1-dependent pathway. Infect Immun 2010; 78:4744-53. [PMID: 20823203 DOI: 10.1128/iai.00744-10] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Microbe-associated molecular patterns are recognized by Toll-like receptors of the innate immune system. This recognition enables a rapid response to potential pathogens but does not clearly provide a way for the innate immune system to discriminate between virulent and avirulent microbes. We find that pulmonary infection of mice with type 3 translocation-competent Pseudomonas aeruginosa triggers a rapid inflammatory response, while infection with isogenic translocation-deficient mutants does not. Discrimination between translocon-positive and -negative bacteria requires caspase-1 activity in bone marrow-derived cells and interleukin-1 receptor signaling. Thus, the activation of caspase-1 by bacteria expressing type 3 secretion systems allows for rapid recognition of bacteria expressing conserved functions associated with virulence.
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Murray TS, Ledizet M, Kazmierczak BI. Swarming motility, secretion of type 3 effectors and biofilm formation phenotypes exhibited within a large cohort of Pseudomonas aeruginosa clinical isolates. J Med Microbiol 2010; 59:511-520. [PMID: 20093376 DOI: 10.1099/jmm.0.017715-0] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Pseudomonas aeruginosa is an opportunistic Gram-negative pathogen capable of acutely infecting or persistently colonizing susceptible hosts. P. aeruginosa colonizes surfaces in vitro by either biofilm formation or swarming motility. The choice of behaviour is influenced by the physical properties of the surface and specific nutrient availability, and subject to regulatory networks that also govern type 2 and type 3 protein secretion. Biofilm formation by clinical isolates has been well-studied. However, the swarming behaviour of human isolates has not been extensively analysed. We collected isolates from 237 hospitalized patients without cystic fibrosis and analysed motility and secretion phenotypes of each isolate. We found biofilm formation and swarming to be negatively associated, while swarming was positively associated with the secretion of both proteases and type 3 exoenzymes. Most isolates were capable of type 3 secretion and biofilm formation, even though these traits are considered to favour distinct modes of pathogenesis. Our data demonstrate that while clinical isolates display diverse motility, biofilm and secretion phenotypes, many of the predicted relationships between swarming motility and other phenotypes observed in laboratory strains also hold true for bacteria isolated from human patients.
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Affiliation(s)
- Thomas S Murray
- Department of Pediatrics and Laboratory Medicine (Infectious Diseases and Clinical Microbiology), Yale University School of Medicine, New Haven, CT 06520, USA
| | | | - Barbara I Kazmierczak
- Section of Microbial Pathogenesis, Yale University School of Medicine, New Haven, CT 06520, USA.,Department of Medicine (Infectious Diseases), Yale University School of Medicine, New Haven, CT 06520, USA
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Abstract
The Gram-negative bacterium Pseudomonas aeruginosa uses a complex type III secretion apparatus to inject effector proteins into host cells. The configuration of this secretion machinery, the activities of the proteins that are injected by it and the consequences of this process for infection are now being elucidated. This Review summarizes our current knowledge of P. aeruginosa type III secretion, including the secretion and translocation machinery, the regulation of this machinery, and the associated chaperones and effector proteins. The features of this interesting secretion system have important implications for the pathogenesis of P. aeruginosa infections and for other type III secretion systems.
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Affiliation(s)
- Alan R Hauser
- Departments of MicrobiologyImmunology and Medicine, Northwestern University, Chicago, Illinois 60611, USA.
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Diverse type III secretion phenotypes among Pseudomonas aeruginosa strains upon infection of murine macrophage-like and endothelial cell lines. Microb Pathog 2007; 44:448-58. [PMID: 18221854 DOI: 10.1016/j.micpath.2007.11.008] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2007] [Revised: 11/19/2007] [Accepted: 11/29/2007] [Indexed: 11/23/2022]
Abstract
The interaction of over 100 isolates of Pseudomonas aeruginosa representing different genotypes of type III secretion system (TTSS) with RAW 264.7 murine macrophage-like cells and pulmonary microvascular endothelial (PME) cells were studied. The strains were isolated from clinical materials and from stool specimens of healthy carriers and were analyzed by pulsed field gel electrophoresis (PFGE) to characterize their heterogeneity. In order to differentiate TTSS genotypes of P. aeruginosa isolates, the distribution of the following genes: exoU, exoS, pcrV, exoT, and exoY was assessed by multiplex and duplex PCR assays. The cytotoxicity and invasiveness of the P. aeruginosa isolates were determined. P. aeruginosa isolates showed a discrepancy in their ability to induce cytotoxicity and to invade mammalian cells. Up to four phenotypes among the isolates were observed and the most diverse interactions of the isolates were noticed with PME cells. The reduction of the viability of the cells, infected by P. aeruginosa isolates of the same clone, was associated with the ability of these strains to secrete the TTSS effectors: ExoU or ExoS. The results of this study also suggest that healthy people can be the carriers of cytotoxic strains of this dangerous pathogen.
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Abstract
Type III secretion systems (T3SSs) are complex bacterial structures that provide gram-negative pathogens with a unique virulence mechanism enabling them to inject bacterial effector proteins directly into the host cell cytoplasm, bypassing the extracellular milieu. Although the effector proteins vary among different T3SS pathogens, common pathogenic mechanisms emerge, including interference with the host cell cytoskeleton to promote attachment and invasion, interference with cellular trafficking processes, cytotoxicity and barrier dysfunction, and immune system subversion. The activity of the T3SSs correlates closely with infection progression and outcome, both in animal models and in human infection. Therefore, to facilitate patient care and improve outcomes, it is important to understand the T3SS-mediated virulence processes and to target T3SSs in therapeutic and prophylactic development efforts.
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Wareham DW, Curtis MA. A genotypic and phenotypic comparison of type III secretion profiles of Pseudomonas aeruginosa cystic fibrosis and bacteremia isolates. Int J Med Microbiol 2007; 297:227-34. [PMID: 17412636 DOI: 10.1016/j.ijmm.2007.02.004] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2006] [Revised: 02/21/2007] [Accepted: 02/23/2007] [Indexed: 11/23/2022] Open
Abstract
The type III secretion system (TTSS) of Pseudomonas aeruginosa enables delivery of a number of toxins involved in the disruption of eukaryotic epithelial surfaces. Whilst the ability to secrete ExoS facilitates invasion and internalization, the secretion of ExoU mediates acute cytotoxicity. In order to determine any association with the ability to secrete these toxins with the nature and severity of human infection, the TTSS genotypes and phenotypes of 163 clinical isolates were determined by multiplex PCR and Western blotting. An exoS+/exoU- genotype was associated with chronic infection in patients with cystic fibrosis whilst an exoS-/exoU+ genotype was associated with strains isolated from blood. Secretion of the ExoU protein was more commonly seen in isolates obtained from blood, suggesting this ability may be important in the development of acute invasive infection. Detection of TTSS toxins in clinical material may be useful in targeting antimicrobial therapy or identifying individuals infected with aggressive strains of P. aeruginosa.
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Affiliation(s)
- David W Wareham
- Centre for Infectious Disease, Institute of Cell and Molecular Science, Barts and The London, Queen Mary's School of Medicine and Dentistry, London E1 2AT, UK.
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Laskowski MA, Kazmierczak BI. Mutational analysis of RetS, an unusual sensor kinase-response regulator hybrid required for Pseudomonas aeruginosa virulence. Infect Immun 2006; 74:4462-73. [PMID: 16861632 PMCID: PMC1539586 DOI: 10.1128/iai.00575-06] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Pseudomonas aeruginosa is an opportunistic pathogen capable of causing both acute and chronic infections in a wide range of hosts. Expression of the type III secretion system (T3SS) proteins is correlated with virulence in models of acute infection, while downregulation of the T3SS and upregulation of genes important for biofilm formation are observed during chronic infections. RetS, a hybrid sensor kinase-response regulator protein of P. aeruginosa, plays a key role in the reciprocal regulation of virulence factors required for acute versus chronic infection and is postulated to act in concert with two other sensor kinase-response regulator hybrids, GacS and LadS. This work examines the roles of the putative sensing and signal transduction domains of RetS in induction of the T3SS in vitro and in a murine model of acute pneumonia. We identify distinct signaling roles for the tandem receiver domains of RetS and present evidence suggesting that RetS may serve as a substrate for another sensor kinase. Phenotypes associated with RetS alleles lacking periplasmic and/or transmembrane domains further indicate that the periplasmic domain of RetS may transmit a signal that inhibits RetS activity during acute infections.
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Affiliation(s)
- Michelle A Laskowski
- Program in Microbiology, Yale University School of Medicine, 333 Cedar Street, P.O. Box 208022, New Haven, Connecticut 06520-8022, USA
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Zaborina O, Kohler JE, Wang Y, Bethel C, Shevchenko O, Wu L, Turner JR, Alverdy JC. Identification of multi-drug resistant Pseudomonas aeruginosa clinical isolates that are highly disruptive to the intestinal epithelial barrier. Ann Clin Microbiol Antimicrob 2006; 5:14. [PMID: 16762075 PMCID: PMC1513249 DOI: 10.1186/1476-0711-5-14] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2006] [Accepted: 06/08/2006] [Indexed: 12/01/2022] Open
Abstract
Background Multi-drug resistant Pseudomonas aeruginosa nosocomial infections are increasingly recognized worldwide. In this study, we focused on the virulence of multi-drug resistant clinical strains P. aeruginosa against the intestinal epithelial barrier, since P. aeruginosa can cause lethal sepsis from within the intestinal tract of critically ill and immuno-compromised patients via mechanisms involving disruption of epithelial barrier function. Methods We screened consecutively isolated multi-drug resistant P. aeruginosa clinical strains for their ability to disrupt the integrity of human cultured intestinal epithelial cells (Caco-2) and correlated these finding to related virulence phenotypes such as adhesiveness, motility, biofilm formation, and cytotoxicity. Results Results demonstrated that the majority of the multi-drug resistant P. aeruginosa clinical strains were attenuated in their ability to disrupt the barrier function of cultured intestinal epithelial cells. Three distinct genotypes were found that displayed an extreme epithelial barrier-disrupting phenotype. These strains were characterized and found to harbor the exoU gene and to display high swimming motility and adhesiveness. Conclusion These data suggest that detailed phenotypic analysis of the behavior of multi-drug resistant P. aeruginosa against the intestinal epithelium has the potential to identify strains most likely to place patients at risk for lethal gut-derived sepsis. Surveillance of colonizing strains of P. aeruginosa in critically ill patients beyond antibiotic sensitivity is warranted.
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Affiliation(s)
- Olga Zaborina
- Department of Surgery, University of Chicago, Chicago, USA
| | | | - Yingmin Wang
- Department of Pathology, University of Chicago, Chicago, USA
| | - Cindy Bethel
- Clinical Microbiology Laboratories, University of Chicago, Chicago, USA
| | | | - Licheng Wu
- Department of Surgery, University of Chicago, Chicago, USA
| | | | - John C Alverdy
- Department of Surgery, University of Chicago, Chicago, USA
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