Large-Scale Identification of Genes Required for Full Virulence of<i>Staphylococcus aureus</i>

Benton, Bret M.; Zhang, J. P.; Bond, Skip; Pope, Casey; Christian, Todd; Lee, Lawrence; Winterberg, Kelly M.; Schmid, Molly B.; Buysse, Jerry M.

doi:10.1128/jb.186.24.8478-8489.2004

Cited by 105 publications

(94 citation statements)

References 62 publications

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“…CI is a sensitive measure of the relative degree of virulence attenuation of a particular mutant in mixed infections with the wild-type strain (Benton et al, 2004). To provide more data about the virulence of the mutants, CI was determined in vivo, using an established mouse subcutaneous model of infection (Horsburgh et al, 2001).…”

Section: Resultsmentioning

confidence: 99%

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Simultaneous lack of catalase and beta-toxin in Staphylococcus aureus leads to increased intracellular survival in macrophages and epithelial cells and to attenuated virulence in murine and ovine models

et al. 2009

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Staphylococcus aureus produces a variety of virulence factors that allow it to cause a wide range of infections in humans and animals. In the latter, S. aureus is a leading cause of intramammary infections. The contribution of catalase (KatA), an enzyme implicated in oxidative stress resistance, and beta-toxin (Hlb), a haemolysin, to the pathogenesis of S. aureus is poorly characterized. To investigate the role of these enzymes as potential virulence factors in S. aureus, we examined the intracellular survival of DkatA, Dhlb and DkatA Dhlb mutants in murine macrophages (J774A.1) and bovine mammary epithelial cells (MAC-T), and their virulence in different murine and ovine models. Catalase was not required for the survival of S. aureus within either J774A.1 or MAC-T cells. However, it was necessary for the intracellular proliferation of the bacterium after invasion of MAC-T cells. In addition, catalase was not needed for the full virulence of S. aureus in mice. Deletion of the hlb gene had no effect on the intracellular survival of S. aureus in J774A.1 cells but did cause a slight increase in survival in MAC-T cells. Furthermore, like catalase, beta-toxin was not required for complete virulence of S. aureus in murine models. Unexpectedly, the DkatA Dhlb mutant showed a notably increased persistence in both cell lines, and was significantly less virulent for mice than were the wild-type strain and single mutants. Most interestingly, it was also markedly attenuated in intramammary and subcutaneous infections in ewes and lambs.

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Section: Resultsmentioning

confidence: 99%

“…CI was measured as described previously (Benton et al, 2004) in an established murine abscess model of infection (Horsburgh et al, 2001), with the following modifications. Mutant and wild-type strains were separately grown to stationary phase in BHI broth, harvested, washed and resuspended in sterile PBS.…”

Section: Methodsmentioning

confidence: 99%

Simultaneous lack of catalase and beta-toxin in Staphylococcus aureus leads to increased intracellular survival in macrophages and epithelial cells and to attenuated virulence in murine and ovine models

et al. 2009

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“…Genome scanning has predicted 17 potential TCSs in S. aureus, some of which have been reported to be regulators of bacterial virulence. The AgrCA TCS is a well-known global regulatory system controlling numerous genes involved in S. aureus virulence, such as cytotoxin-and hemolysin-encoding genes, but other TCSs, such as ArlSR, SaeSR, VraSR, and SsrAB, have also been reported to play roles in S. aureus virulence (2,32,41).…”

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New Insights into the WalK/WalR (YycG/YycF) Essential Signal Transduction Pathway Reveal a Major Role in Controlling Cell Wall Metabolism and Biofilm Formation inStaphylococcus aureus

et al. 2007

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The highly conserved WalK/WalR (also known as YycG/YycF) two-component system is specific to low-G؉C gram-positive bacteria. While this system is essential for cell viability, both the nature of its regulon and its physiological role have remained mostly uncharacterized. We observed that, unexpectedly, Staphylococcus aureus cell death induced by WalKR depletion was not followed by lysis. We show that WalKR positively controls autolytic activity, in particular that of the two major S. aureus autolysins, AtlA and LytM. By using our previously characterized consensus WalR binding site and carefully reexamining the genome annotations, we identified nine genes potentially belonging to the WalKR regulon that appeared to be involved in S. aureus cell wall degradation. Expression of all of these genes was positively controlled by WalKR levels in the cell, leading to high resistance to Triton X-100-induced lysis when the cells were starved for WalKR. Cells lacking WalKR were also more resistant to lysostaphin-induced lysis, suggesting modifications in cell wall structure. Indeed, lowered levels of WalKR led to a significant decrease in peptidoglycan biosynthesis and turnover and to cell wall modifications, which included increased peptidoglycan cross-linking and glycan chain length. We also demonstrated a direct relationship between WalKR levels and the ability to form biofilms. This is the first example in S. aureus of a regulatory system positively controlling autolysin synthesis and biofilm formation. Taken together, our results now define this signal transduction pathway as a master regulatory system for cell wall metabolism, which we have accordingly renamed WalK/WalR to reflect its true function.

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“…Microarray analysis and proteomics have revealed that most of the genes activated by sae are involved in bacterial adhesion, immune modulation, or toxicity (25,29,38). In addition, the importance of gene regulation by sae in vivo was shown in several animal models (3,15,16,29,43).The sae locus consists of four open reading frames, two of which (saeR and saeS) show strong sequence homology to response regulators and to histidine kinases (HKs) of bacterial two-component regulators (10). Two additional open reading frames, saeP and saeQ, both located upstream of saeRS, are likely to be important for the functionality of the sae operon (33, 39).…”

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The Virulence Regulator Sae ofStaphylococcus aureus:Promoter Activities and Response to Phagocytosis-Related Signals

et al. 2008

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The two-component system SaeRS of Staphylococcus aureus is closely involved in the regulation of major virulence factors. However, little is known about the signals leading to saeRS activation. A total of four overlapping transcripts (T1 to T4) from three different transcription starting points are expressed in the sae operon. We used a ␤-galactosidase reporter assay to characterize the putative promoter regions within the saeRS upstream region. The main transcript T2 is probably generated by endoribonucleolytic processing of the T1 transcript. Only two distinct promoter elements (P1 and P3) could be detected within the saeRS upstream region. The P3 promoter, upstream of saeRS, generates the T3 transcript, includes a cis-acting enhancer element and is repressed by saeRS. The most distal P1 promoter is strongly autoregulated, activated by agr, and repressed by sigma factor B. In strain Newman a mutation within the histidine kinase SaeS leads to a constitutively activated sae system. Evaluation of different external signals revealed that the P1 promoter in strain ISP479R and strain UAMS-1 is inhibited by low pH and high NaCl concentrations but activated by hydrogen peroxide. The most prominent induction of P1 was observed at subinhibitory concentrations of ␣-defensins in various S. aureus strains, with the exception of strain ISP479R and strain COL. P1 was not activated by the antimicrobial peptides LL37 and daptomycin. In summary, the results indicate that the sensor molecule SaeS is activated by alteration within the membrane allowing the pathogen to react to phagocytosis related effector molecules.Staphylococcus aureus asymptomatically colonizes the noses of healthy individuals but also causes a variety of infections in humans. Polymorphonuclear neutrophils (PMNs) provide an effective line of defense against infections. However, S. aureus has developed a variety of mechanisms to avoid being killed by PMNs, including the expression of a number of immune modulators and toxins (for a review, see reference 8). The expression of most virulence and adherence factors is directly or indirectly influenced by diverse regulators such as agr, the alternative sigma factor B (SigB), sarA homologues or sae (for reviews, see references 4, 6, 17, and 32). Within this network sae appears to be a central downstream regulator that controls the expression of major virulence genes such as hla (coding for alpha-hemolysin), coa (coding for coagulase), or fnbA (coding for fibronectin-binding protein A) (11,33,39). Microarray analysis and proteomics have revealed that most of the genes activated by sae are involved in bacterial adhesion, immune modulation, or toxicity (25,29,38). In addition, the importance of gene regulation by sae in vivo was shown in several animal models (3,15,16,29,43).The sae locus consists of four open reading frames, two of which (saeR and saeS) show strong sequence homology to response regulators and to histidine kinases (HKs) of bacterial two-component regulators (10). Two additional open reading frames, saeP ...

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Large-Scale Identification of Genes Required for Full Virulence ofStaphylococcus aureus

Cited by 105 publications

References 62 publications

Simultaneous lack of catalase and beta-toxin in Staphylococcus aureus leads to increased intracellular survival in macrophages and epithelial cells and to attenuated virulence in murine and ovine models

Simultaneous lack of catalase and beta-toxin in Staphylococcus aureus leads to increased intracellular survival in macrophages and epithelial cells and to attenuated virulence in murine and ovine models

New Insights into the WalK/WalR (YycG/YycF) Essential Signal Transduction Pathway Reveal a Major Role in Controlling Cell Wall Metabolism and Biofilm Formation inStaphylococcus aureus

The Virulence Regulator Sae ofStaphylococcus aureus:Promoter Activities and Response to Phagocytosis-Related Signals

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