401
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Kennedy AD, Willment JA, Dorward DW, Williams DL, Brown GD, DeLeo FR. Dectin-1 promotes fungicidal activity of human neutrophils. Eur J Immunol 2007; 37:467-78. [PMID: 17230442 DOI: 10.1002/eji.200636653] [Citation(s) in RCA: 92] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Human polymorphonuclear leukocytes (PMN) are a first line of defense against fungal infections. PMN express numerous pattern recognition receptors (PRR) that facilitate identification of invading microorganisms and ultimately promote resolution of disease. Dectin-1 (beta-glucan receptor) is a PRR expressed on several cell types and has been studied on monocytes and macrophages. However, the role played by dectin-1 in the recognition and killing of fungi by PMN is unknown. We investigated the ability of dectin-1 to mediate human PMN phagocytosis and fungicidal activity. Dectin-1 was expressed on the surface of PMN from all subjects tested (n=29) and in an intracellular compartment that co-sedimented with azurophilic granules in Percoll density gradients. Soluble beta-glucan and mAb GE2 (anti-dectin-1) inhibited binding and phagocytosis of zymosan by human PMN (e.g., ingestion was inhibited 40.1% by 30 min, p<0.001), and blocked reactive oxygen species production. Notably, soluble beta-glucan and GE2 inhibited phagocytosis and killing of Candida albicans by PMN (inhibition of killing was 54.8% for beta-glucan and 36.2% for GE2, p<0.01). Our results reveal a mechanism whereby PMN dectin-1 plays a key role in the recognition and killing of fungal pathogens by the innate immune system.
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Affiliation(s)
- Adam D Kennedy
- Laboratory of Human Bacterial Pathogenesis, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, MT 59840, USA
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402
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Reniere ML, Torres VJ, Skaar EP. Intracellular metalloporphyrin metabolism in Staphylococcus aureus. Biometals 2007; 20:333-45. [PMID: 17387580 DOI: 10.1007/s10534-006-9032-0] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2006] [Accepted: 07/20/2006] [Indexed: 01/11/2023]
Abstract
The bacterial pathogen Staphylococcus aureus is responsible for a significant amount of human morbidity and mortality, and the ability of S. aureus to cause disease is absolutely dependent on the acquisition of iron from the host. The most abundant iron source to invading staphylococci is in the form of the porphyrin heme. S. aureus is capable of acquiring nutrient iron from heme and hemoproteins via two heme-acquisition systems, the iron-regulated surface determinant system (Isd) and the heme transport system (Hts). Heme acquisition through these systems is involved in staphylococcal pathogenesis suggesting that the intracellular fate of heme plays a significant role in the infectious process. The valuable heme molecule presents a paradox to invading bacteria because although heme is an abundant source of nutrient iron, the extreme reactivity of heme makes it toxic at high concentrations. Therefore, bacteria must regulate the levels of intracellular heme to avoid toxicity. Although the molecular mechanisms responsible for staphylococcal heme acquisition are beginning to emerge, the mechanisms by which S. aureus regulate intracellular heme homeostasis are largely unknown. In this review we describe three potential fates of host-derived heme acquired by S. aureus during infection: (i) degradation for use as a nutrient iron source, (ii) incorporation into bacterial heme-binding proteins for use as an enzyme cofactor, or (iii) efflux through a dedicated ABC-type transport system. We hypothesize that the ultimate fate of exogenously acquired heme in S. aureus is dependent upon the intracellular and extracellular availability of both iron and heme.
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Affiliation(s)
- Michelle L Reniere
- Department of Microbiology and Immunology, Vanderbilt University Medical Center, 1161, 21st Avenue South, MCN A5102, Nashville, TN 37232, USA
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403
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Ruhe JJ, Smith N, Bradsher RW, Menon A. Community-Onset Methicillin-Resistant Staphylococcus aureus Skin and Soft-Tissue Infections: Impact of Antimicrobial Therapy on Outcome. Clin Infect Dis 2007; 44:777-84. [PMID: 17304447 DOI: 10.1086/511872] [Citation(s) in RCA: 149] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2006] [Accepted: 10/23/2006] [Indexed: 01/15/2023] Open
Abstract
BACKGROUND Conflicting data exist on the role of antimicrobial therapy for the treatment of uncomplicated community-onset methicillin-resistant Staphylococcus aureus (MRSA) skin and soft-tissue infections (SSTIs). METHODS We performed a retrospective cohort study of 492 adult patients with 531 independent episodes of community-onset MRSA SSTIs, which consisted of abscesses, furuncles/carbuncles, and cellulitis, at 2 tertiary care medical centers. The purpose of the study was to determine the impact of active antimicrobial therapy (i.e., the use of an agent to which the organism is susceptible) and other potential risk factors on the outcome for patients with uncomplicated community-onset MRSA SSTIs. Treatment failure was the primary outcome of interest and was defined as worsening signs of infection associated with microbiological and/or therapeutic indicators of an unsuccessful outcome. Bivariate analyses and logistic regression analyses were preformed to determine predictors of treatment failure. RESULTS An incision and drainage procedure was performed for the majority of patients. Treatment failure occurred in 45 (8%) of 531 episodes of community-onset MRSA SSTI. Therapy was successful for 296 (95%) of 312 patients who received an active antibiotic, compared with 190 (87%) of 219 of those who did not (P=.001 in bivariate analysis). Use of an inactive antimicrobial agent was an independent predictor of treatment failure on logistic regression analysis (adjusted odds ratio, 2.80; 95% confidence interval, 1.26-6.22; P=.01). CONCLUSIONS Our findings suggest that certain patients with SSTIs that are likely caused by MRSA would benefit from treatment with an antimicrobial agent with activity against this organism.
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Affiliation(s)
- Jörg J Ruhe
- Division of Infectious Diseases, Department of Medicine, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA.
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404
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Modulation of virulence gene expression in Staphylococcus aureus by interleukin-1β: Novel implications in bacterial pathogenesis. Microbes Infect 2007; 9:408-15. [DOI: 10.1016/j.micinf.2006.12.018] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2006] [Revised: 11/08/2006] [Accepted: 12/18/2006] [Indexed: 12/15/2022]
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405
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Korem M, Gov Y, Shirron N, Shuster A, Rosenberg M. Alcohol increases hemolysis by staphylococci. FEMS Microbiol Lett 2007; 269:153-9. [PMID: 17227454 DOI: 10.1111/j.1574-6968.2006.00625.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
It was recently found that alcohols can confer hemolytic properties on certain species of yeast. Here, it is reported that alcohol can promote hemolysis by various species of staphylococci, including strains of Staphylococcus aureus, Staphylococcus epidermidis and Staphylococcus hominis. In order to study this novel phenomenon in S. aureus and S. epidermidis, strains that exhibit this phenomenon (e.g. S. aureus 8325-4, COL, SH1000, S. epidermidis), as compared with strains that exhibited little alcohol-enhanced hemolysis (e.g. S. aureus 8325-4 DeltaTRAP, RN6911) were examined. Both ethanol and n-butanol caused upregulation of the virulence regulator-RNAIII, with a concomitant increase in the production of alpha, beta and gamma-hemolysins in strain 8325-4. In S. aureus COL and SH1000, there was an increase in RNAIII but no change in transcription levels of alpha, beta and gamma hemolysins. Staphylococcus epidermidis stain sofi exhibited increased RNAIII and beta hemolysin production. Staphylococcus aureus mutant strains (8325-4 DeltaTRAP and RN6911) showed no change in the transcription level of the RNAIII regulator and the above hemolysins. Increased hemolysis in S. aureus COL, SH1000 and mutant strains may be caused by other hemolysins (not regulated by RNAIII) or through other mechanisms such as hyperoxidation or cytotoxic lipids.
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Affiliation(s)
- Moshe Korem
- Department of Human Microbiology, Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel
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406
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Burlak C, Hammer CH, Robinson MA, Whitney AR, McGavin MJ, Kreiswirth BN, DeLeo FR. Global analysis of community-associated methicillin-resistant Staphylococcus aureus exoproteins reveals molecules produced in vitro and during infection. Cell Microbiol 2007; 9:1172-90. [PMID: 17217429 PMCID: PMC2064037 DOI: 10.1111/j.1462-5822.2006.00858.x] [Citation(s) in RCA: 122] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) is a threat to human health worldwide. Although progress has been made, mechanisms of CA-MRSA pathogenesis are poorly understood and a comprehensive analysis of CA-MRSA exoproteins has not been conducted. To address that deficiency, we used proteomics to identify exoproteins made by MW2 (USA400) and LAC (USA300) during growth in vitro. Two hundred and fifty unique exoproteins were identified by 2-dimensional gel electrophoresis coupled with automated direct infusion-tandem mass spectrometry (ADI-MS/MS) analysis. Eleven known virulence-related exoproteins differed in abundance between the strains, including alpha-haemolysin (Hla), collagen adhesin (Cna), staphylokinase (Sak), coagulase (Coa), lipase (Lip), enterotoxin C3 (Sec3), enterotoxin Q (Seq), V8 protease (SspA) and cysteine protease (SspB). Mice infected with MW2 or LAC produced antibodies specific for known or putative virulence factors, such as autolysin (Atl), Cna, Ear, ferritin (Ftn), Lip, 1-phosphatidylinositol phosphodiesterase (Plc), Sak, Sec3 and SspB, indicating the exoproteins are made during infection in vivo. We used confocal microscopy to demonstrate aureolysin (Aur), Hla, SspA and SspB are produced following phagocytosis by human neutrophils, thereby linking exoprotein production in vitro with that during host-pathogen interaction. We conclude that the exoproteins identified herein likely account in part for the success of CA-MRSA as a human pathogen.
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Affiliation(s)
- Christopher Burlak
- Laboratory of Human Bacterial Pathogenesis, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of HealthHamilton, MT 59840, USA.
| | - Carl H Hammer
- Reseach Technologies Branch, Mass Spectrometry Laboratory, National Institute of Allergy and Infectious Diseases, National Institutes of HealthRockville, MD 20852, USA.
| | - Mary-Ann Robinson
- Reseach Technologies Branch, Mass Spectrometry Laboratory, National Institute of Allergy and Infectious Diseases, National Institutes of HealthRockville, MD 20852, USA.
| | - Adeline R Whitney
- Laboratory of Human Bacterial Pathogenesis, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of HealthHamilton, MT 59840, USA.
| | - Martin J McGavin
- University of Toronto, Department of Laboratory Medicine and Pathobiology, and Sunnybrook Health Sciences CentreToronto, ON, Canada, M4N 3M5.
| | - Barry N Kreiswirth
- Public Health Research Institute Tuberculosis Center, International Center for Public HealthNewark, NJ 07103, USA.
| | - Frank R DeLeo
- Laboratory of Human Bacterial Pathogenesis, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of HealthHamilton, MT 59840, USA.
- *For correspondence. E-mail ; Tel. (+1) 406 363 9448; Fax (+1) 406 363 9394
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407
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Boyle-Vavra S, Daum RS. Community-acquired methicillin-resistant Staphylococcus aureus: the role of Panton-Valentine leukocidin. J Transl Med 2007; 87:3-9. [PMID: 17146447 DOI: 10.1038/labinvest.3700501] [Citation(s) in RCA: 336] [Impact Index Per Article: 19.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Community-acquired (CA) methicillin-resistant Staphylococcus aureus (MRSA) infection among individuals without healthcare-associated (HA) risk factors was first recognized about a decade ago. It has now emerged as an epidemic that is responsible for rapidly progressive, fatal diseases including necrotizing pneumonia, severe sepsis and necrotizing fasciitis. Unlike HA-MRSA, CA-MRSA are usually pan-susceptible to non-beta-lactam antimicrobials. In addition to novel methicillin resistance genetic cassettes, many CA-MRSA harbor a phage harboring Panton-Valentine Leukocidin (PVL) genes and some data support the idea that PVL is responsible at least in part for the increased virulence of CA-MRSA. The tight association between the novel methicillin resistance cassettes and PVL phage cannot be explained, as they integrate into distinct sites on the S. aureus chromosome. This paper presents the evidence that CA-MRSA isolates are distinct strains emerging de novo from CA-methicillin susceptible isolates rather than from HA-MRSA isolates that have escaped from the hospital setting and that these novel CA-MRSA isolates may be more virulent than HA-MRSA. The second aim is to outline the progress in understanding the role of PVL in CA-MRSA pathogenesis.
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Affiliation(s)
- Susan Boyle-Vavra
- Department of Pediatrics, Section of Infectious Diseases, University of Chicago, Chicago, IL 60637, USA.
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408
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Schnappinger D. Genomics of host-pathogen interactions. PROGRESS IN DRUG RESEARCH. FORTSCHRITTE DER ARZNEIMITTELFORSCHUNG. PROGRES DES RECHERCHES PHARMACEUTIQUES 2007; 64:311, 313-43. [PMID: 17195480 DOI: 10.1007/978-3-7643-7567-6_12] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
The complete sequences of hundreds of microbial genomes have provided drug discovery pipelines with thousands of new potential drug targets. Their availability has also stimulated the development of a variety of innovative approaches that allow functional studies to be performed on the entire genome of an organism. This chapter describes how these approaches have been applied to the analysis of host-pathogen interactions and discusses how such studies might facilitate the development of new antibiotics.
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Affiliation(s)
- Dirk Schnappinger
- Department of Microbiology and Immunology, Weill Medical College of Cornell University, New York, USA.
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409
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Cirz RT, Jones MB, Gingles NA, Minogue TD, Jarrahi B, Peterson SN, Romesberg FE. Complete and SOS-mediated response of Staphylococcus aureus to the antibiotic ciprofloxacin. J Bacteriol 2006; 189:531-9. [PMID: 17085555 PMCID: PMC1797410 DOI: 10.1128/jb.01464-06] [Citation(s) in RCA: 180] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Staphylococcus aureus infections can be difficult to treat due to both multidrug resistance and the organism's remarkable ability to persist in the host. Persistence and the evolution of resistance may be related to several complex regulatory networks, such as the SOS response, which modifies transcription in response to environmental stress. To understand how S. aureus persists during antibiotic therapy and eventually emerges resistant, we characterized its global transcriptional response to ciprofloxacin. We found that ciprofloxacin induces prophage mobilization as well as significant alterations in metabolism, most notably the up-regulation of the tricarboxylic acid cycle. In addition, we found that ciprofloxacin induces the SOS response, which we show, by comparison of a wild-type strain and a non-SOS-inducible lexA mutant strain, includes the derepression of 16 genes. While the SOS response of S. aureus is much more limited than those of Escherichia coli and Bacillus subtilis, it is similar to that of Pseudomonas aeruginosa and includes RecA, LexA, several hypothetical proteins, and a likely error-prone Y family polymerase whose homologs in other bacteria are required for induced mutation. We also examined induced mutation and found that either the inability to derepress the SOS response or the lack of the LexA-regulated polymerase renders S. aureus unable to evolve antibiotic resistance in vitro in response to UV damage. The data suggest that up-regulation of the tricarboxylic acid cycle and induced mutation facilitate S. aureus persistence and evolution of resistance during antibiotic therapy.
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Affiliation(s)
- Ryan T Cirz
- Department of Chemistry, The Scripps Research Institute, La Jolla, CA 92037, USA
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410
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Abstract
Many microbial pathogens evolved to circumvent the attack of neutrophils, which are essential effector cells of the innate immune system. Here we review six major strategies that pathogenic bacteria and fungi use to evade neutrophil defences: (i) turning on survival and stress responses, (ii) avoiding contact, (iii) preventing phagocytosis, (iv) surviving intracellularly, (v) inducing cell death and (vi) evading killing by neutrophil extracellular traps. For each category we give examples and further focus on one particular pathogenic microbe in more detail. Pathogens include Candida albicans, Cryptococcus neoformans, Yersinia ssp., Helicobacter pylori, Staphylococcus aureus, Streptococcus pyogenes and Streptococcus pneumoniae.
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Affiliation(s)
- Constantin F Urban
- Department of Cellular Microbiology, Max Planck Institute for Infection Biology, Charitéplatz 1, 10117 Berlin, Germany
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411
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Sibbald MJJB, Ziebandt AK, Engelmann S, Hecker M, de Jong A, Harmsen HJM, Raangs GC, Stokroos I, Arends JP, Dubois JYF, van Dijl JM. Mapping the pathways to staphylococcal pathogenesis by comparative secretomics. Microbiol Mol Biol Rev 2006; 70:755-88. [PMID: 16959968 PMCID: PMC1594592 DOI: 10.1128/mmbr.00008-06] [Citation(s) in RCA: 204] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
The gram-positive bacterium Staphylococcus aureus is a frequent component of the human microbial flora that can turn into a dangerous pathogen. As such, this organism is capable of infecting almost every tissue and organ system in the human body. It does so by actively exporting a variety of virulence factors to the cell surface and extracellular milieu. Upon reaching their respective destinations, these virulence factors have pivotal roles in the colonization and subversion of the human host. It is therefore of major importance to obtain a clear understanding of the protein transport pathways that are active in S. aureus. The present review aims to provide a state-of-the-art roadmap of staphylococcal secretomes, which include both protein transport pathways and the extracytoplasmic proteins of these organisms. Specifically, an overview is presented of the exported virulence factors, pathways for protein transport, signals for cellular protein retention or secretion, and the exoproteomes of different S. aureus isolates. The focus is on S. aureus, but comparisons with Staphylococcus epidermidis and other gram-positive bacteria, such as Bacillus subtilis, are included where appropriate. Importantly, the results of genomic and proteomic studies on S. aureus secretomes are integrated through a comparative "secretomics" approach, resulting in the first definition of the core and variant secretomes of this bacterium. While the core secretome seems to be largely employed for general housekeeping functions which are necessary to thrive in particular niches provided by the human host, the variant secretome seems to contain the "gadgets" that S. aureus needs to conquer these well-protected niches.
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Affiliation(s)
- M J J B Sibbald
- Department of Medical Microbiology, University Medical Centre Groningen, Groningen, The Netherlands
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412
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Anderson KL, Roberts C, Disz T, Vonstein V, Hwang K, Overbeek R, Olson PD, Projan SJ, Dunman PM. Characterization of the Staphylococcus aureus heat shock, cold shock, stringent, and SOS responses and their effects on log-phase mRNA turnover. J Bacteriol 2006; 188:6739-56. [PMID: 16980476 PMCID: PMC1595530 DOI: 10.1128/jb.00609-06] [Citation(s) in RCA: 205] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Despite its being a leading cause of nosocomal and community-acquired infections, surprisingly little is known about Staphylococcus aureus stress responses. In the current study, Affymetrix S. aureus GeneChips were used to define transcriptome changes in response to cold shock, heat shock, stringent, and SOS response-inducing conditions. Additionally, the RNA turnover properties of each response were measured. Each stress response induced distinct biological processes, subsets of virulence factors, and antibiotic determinants. The results were validated by real-time PCR and stress-mediated changes in antimicrobial agent susceptibility. Collectively, many S. aureus stress-responsive functions are conserved across bacteria, whereas others are unique to the organism. Sets of small stable RNA molecules with no open reading frames were also components of each response. Induction of the stringent, cold shock, and heat shock responses dramatically stabilized most mRNA species. Correlations between mRNA turnover properties and transcript titers suggest that S. aureus stress response-dependent alterations in transcript abundances can, in part, be attributed to alterations in RNA stability. This phenomenon was not observed within SOS-responsive cells.
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Affiliation(s)
- Kelsi L Anderson
- Department of Pathology and Microbiology, University of Nebraska Medical Center, Nebraska 68198, USA
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413
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van Belkum A. Staphylococcal colonization and infection: homeostasis versus disbalance of human (innate) immunity and bacterial virulence. Curr Opin Infect Dis 2006; 19:339-44. [PMID: 16804380 DOI: 10.1097/01.qco.0000235159.40184.61] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
PURPOSE OF REVIEW This review identifies trends in the study of interactions between Staphylococcus aureus and humans. When nasal colonization is in the neutral state, infection clearly represents a state of host-pathogen disbalance. The features leading from apparent homeostatic colonization to pathogenesis are identified at an increasing rate. RECENT FINDINGS Persistent carriage of S. aureus predisposes to infection but limits bacteraemia-associated mortality. Intermittent carriage is usually imposed and of lesser clinical relevance. The nature and function of several staphylococcal virulence factors have been elucidated and near complete gene catalogues have been established. There does not seem to be a difference in virulence, however, between methicillin-susceptible and resistant S. aureus. Biological selection takes place in the nose and innate immune features relevant to colonization have been discovered. Acquired immunity remains underexposed, but the host factors involved in the host-pathogen interaction have been identified. SUMMARY Virulence assessment of S. aureus has been facilitated by novel technology: genome-wide inventories of virulence potential can be made and new pathogenic mechanisms have been presumptively identified. These involve invasion procedures but also (innate) immune evasion strategies. These cross-fertilizing developments shed light on the feasibility of novel prophylactic or therapeutic strategies for combating staphylococcal carriage and disease.
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Affiliation(s)
- Alex van Belkum
- Erasmus MC, Department of Medical Microbiology and Infectious Diseases, Unit Research and Development, Rotterdam, The Netherlands.
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414
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Seidl K, Stucki M, Ruegg M, Goerke C, Wolz C, Harris L, Berger-Bächi B, Bischoff M. Staphylococcus aureus CcpA affects virulence determinant production and antibiotic resistance. Antimicrob Agents Chemother 2006; 50:1183-94. [PMID: 16569828 PMCID: PMC1426959 DOI: 10.1128/aac.50.4.1183-1194.2006] [Citation(s) in RCA: 166] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Carbon catabolite protein A (CcpA) is known to function as a major regulator of gene expression in different gram-positive organisms. Deletion of the ccpA homologue (saCOL1786) in Staphylococcus aureus was found to affect growth, glucose metabolization, and transcription of selected virulence determinants. In liquid culture, deletion of CcpA decreased the growth rate and yield; however, the effect was only transient during the exponential-growth phase as long as glucose was present in the medium. Depletion of glucose and production of lactate was delayed, while the level of excretion of acetate was less affected and was even higher in the mutant culture. On solid medium, in contrast, growth of the DeltaccpA mutant resulted in smaller colonies containing a lower number of CFU per colony. Deletion of CcpA had an effect on the expression of important virulence factors of S. aureus by down-regulating RNAIII, the effector molecule of the agr locus, and altering the transcription patterns of hla, encoding alpha-hemolysin, and spa, encoding protein A. CcpA inactivation markedly reduced the oxacillin resistance levels in the highly methicillin-resistant S. aureus strain COLn and the teicoplanin resistance level in a glycopeptide-intermediate-resistant S. aureus strain. The presence of CcpA in the capsular polysaccharide serotype 5 (CP5)-producing strain Newman abolished capsule formation and decreased cap operon transcription in the presence of glucose. The staphylococcal CcpA thus not only is involved in the regulation of carbon metabolism but seems to function as a modulator of virulence gene expression as well.
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Affiliation(s)
- Kati Seidl
- Department of Medical Microbiology, University of Zürich, Gloriastr. 32, CH-8006 Zürich, Switzerland, and Institute for Medical Microbiology and Hygiene, University Hospital Tübingen, Germany
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415
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Hunt CL, Nauseef WM, Weiss JP. Effect of d-Alanylation of (Lipo)Teichoic Acids ofStaphylococcus aureuson Host Secretory Phospholipase A2Action before and after Phagocytosis by Human Neutrophils. THE JOURNAL OF IMMUNOLOGY 2006; 176:4987-94. [PMID: 16585595 DOI: 10.4049/jimmunol.176.8.4987] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Invading bacteria such as Staphylococcus aureus induce mobilization of professional phagocytes (e.g., neutrophils) and extracellular antibacterial proteins (e.g., group IIA phospholipase A2 (gIIA PLA2)). Accumulation of gIIA PLA2 in inflammatory fluids confers potent extracellular antistaphylococcal activity and at lower concentrations promotes bacterial phospholipid degradation during phagocytosis of S. aureus by human neutrophils. D-alanylation of (lipo) teichoic acids of S. aureus increases bacterial resistance to gIIA PLA2 approximately 100-fold, raising the possibility that the resistance of ingested S. aureus to related gV and gX secretory PLA2 present in human neutrophil granules depends on D-alanylation mediated by the dlt operon. However, we show that isogenic wild-type and dltA S. aureus are equally resistant to gV/X PLA2 during phagocytosis and when exposed to the purified enzymes. The fates of wild-type and dltA S. aureus exposed to serum and human neutrophils differed significantly only when extracellular gIIA PLA2 was also present before phagocytosis. The extreme potency of the gIIA PLA2 toward dltA S. aureus suggests that even small amounts of this extracellular enzyme mobilized early in inflammation could contribute substantially to the overall cytotoxicity of acute inflammatory exudates toward S. aureus when D-alanylation of (lipo)teichoic acids is limiting.
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Affiliation(s)
- Catherine L Hunt
- The Inflammation Program, University of Iowa and Veterans Affairs Medical Center, Iowa City 52242, USA
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416
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Diep BA, Gill SR, Chang RF, Phan TH, Chen JH, Davidson MG, Lin F, Lin J, Carleton HA, Mongodin EF, Sensabaugh GF, Perdreau-Remington F. Complete genome sequence of USA300, an epidemic clone of community-acquired meticillin-resistant Staphylococcus aureus. Lancet 2006; 367:731-9. [PMID: 16517273 DOI: 10.1016/s0140-6736(06)68231-7] [Citation(s) in RCA: 1210] [Impact Index Per Article: 67.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
BACKGROUND USA300, a clone of meticillin-resistant Staphylococcus aureus, is a major source of community-acquired infections in the USA, Canada, and Europe. Our aim was to sequence its genome and compare it with those of other strains of S aureus to try to identify genes responsible for its distinctive epidemiological and virulence properties. METHODS We ascertained the genome sequence of FPR3757, a multidrug resistant USA300 strain, by random shotgun sequencing, then compared it with the sequences of ten other staphylococcal strains. FINDINGS Compared with closely related S aureus, we noted that almost all of the unique genes in USA300 clustered in novel allotypes of mobile genetic elements. Some of the unique genes are involved in pathogenesis, including Panton-Valentine leucocidin and molecular variants of enterotoxin Q and K. The most striking feature of the USA300 genome is the horizontal acquisition of a novel mobile genetic element that encodes an arginine deiminase pathway and an oligopeptide permease system that could contribute to growth and survival of USA300. We did not detect this element, termed arginine catabolic mobile element (ACME), in other S aureus strains. We noted a high prevalence of ACME in S epidermidis, suggesting not only that ACME transfers into USA300 from S epidermidis, but also that this element confers a selective advantage to this ubiquitous commensal of the human skin. INTERPRETATION USA300 has acquired mobile genetic elements that encode resistance and virulence determinants that could enhance fitness and pathogenicity.
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Affiliation(s)
- Binh An Diep
- Department of Medicine, University of California, San Francisco General Hospital, San Francisco, CA 94143, USA.
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Dockrell DH, Whyte MKB. Regulation of phagocyte lifespan in the lung during bacterial infection. J Leukoc Biol 2006; 79:904-8. [PMID: 16478918 DOI: 10.1189/jlb.1005555] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
The innate-immune response to infection is critically dependent on the antimicrobial actions of macrophages and neutrophils. Host and pathogen have evolved strategies to regulate immune-cell antimicrobial functions via alterations in cell death. Modulation of phagocyte death by bacteria is an important pathogenic mechanism. Host benefits of phagocyte apoptosis also exist, and understanding the mechanisms and consequences of apoptosis is essential before we can devise strategies to modulate this element of the innate-immune response to the host's benefit. This is of particular importance in an organ such as the lung, in which the balance between the need to recruit phagocytes to maintain bacterial sterility and the requirement to clear recruited cells from the alveolar units to preserve physiologic gas exchange must be finely tuned to ensure survival during bacterial infection. Apoptosis clearly plays a critical role in reconciling these physiological requirements.
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Affiliation(s)
- David H Dockrell
- Academics Units of Respiratory Medicine and Infectious Diseases, University of Sheffield, Sheffield, UK
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Abstract
Staphylococcus aureus can cause superficial skin infections and, occasionally, deep-seated infections that entail spread through the blood stream. The organism expresses several factors that compromise the effectiveness of neutrophils and macrophages, the first line of defence against infection. S. aureus secretes proteins that inhibit complement activation and neutrophil chemotaxis or that lyse neutrophils, neutralizes antimicrobial defensin peptides, and its cell surface is modified to reduce their effectiveness. The organism can survive in phagosomes, express polysaccharides and proteins that inhibit opsonization by antibody and complement, and its cell wall is resistant to lysozyme. Furthermore, S. aureus expresses several types of superantigen that corrupt the normal humoral immune response, resulting in anergy and immunosuppression. In contrast, Staphylococcus epidermidis must rely primarily on cell-surface polymers and the ability to form a biolfilm to survive in the host.
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Affiliation(s)
- Timothy J Foster
- Microbiology Department, Moyne Institute of Preventive Medicine, Trinity College, Dublin 2, Ireland.
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