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Molecular basis of resistance to muramidase and cationic antimicrobial peptide activity of lysozyme in staphylococci.

ABSTRACT: It has been shown recently that modification of peptidoglycan by O-acetylation renders pathogenic staphylococci resistant to the muramidase activity of lysozyme. Here, we show that a Staphylococcus aureus double mutant defective in O-acetyltransferase A (OatA), and the glycopeptide resistance-associated two-component system, GraRS, is much more sensitive to lysozyme than S. aureus with the oatA mutation alone. The graRS single mutant was resistant to the muramidase activity of lysozyme, but was sensitive to cationic antimicrobial peptides (CAMPs) such as the human lysozyme-derived peptide 107R-A-W-V-A-W-R-N-R115 (LP9), polymyxin B, or gallidermin. A comparative transcriptome analysis of wild type and the graRS mutant revealed that GraRS controls 248 genes. It up-regulates global regulators (rot, sarS, or mgrA), various colonization factors, and exotoxin-encoding genes, as well as the ica and dlt operons. A pronounced decrease in the expression of the latter two operons explains why the graRS mutant is also biofilm-negative. The decrease of the dlt transcript in the graRS mutant correlates with a 46.7% decrease in the content of esterified d-alanyl groups in teichoic acids. The oatA/dltA double mutant showed the highest sensitivity to lysozyme; this mutant completely lacks teichoic acid-bound d-alanine esters, which are responsible for the increased susceptibility to CAMPs and peptidoglycan O-acetylation. Our results demonstrate that resistance to lysozyme can be dissected into genes mediating resistance to its muramidase activity (oatA) and genes mediating resistance to CAMPs (graRS and dlt). The two lysozyme activities act synergistically, as the oatA/dltA or oatA/graRS double mutants are much more susceptible to lysozyme than each of the single mutants.

SUBMITTER: Herbert S

PROVIDER: S-EPMC1933452 | biostudies-literature | 2007 Jul

REPOSITORIES: biostudies-literature

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Molecular basis of resistance to muramidase and cationic antimicrobial peptide activity of lysozyme in staphylococci.

Herbert Silvia S Bera Agnieszka A Nerz Christiane C Kraus Dirk D Peschel Andreas A Goerke Christiane C Meehl Michael M Cheung Ambrose A Götz Friedrich F

PLoS pathogens 20070701 7

It has been shown recently that modification of peptidoglycan by O-acetylation renders pathogenic staphylococci resistant to the muramidase activity of lysozyme. Here, we show that a Staphylococcus aureus double mutant defective in O-acetyltransferase A (OatA), and the glycopeptide resistance-associated two-component system, GraRS, is much more sensitive to lysozyme than S. aureus with the oatA mutation alone. The graRS single mutant was resistant to the muramidase activity of lysozyme, but was ...[more]

PMID: 17676995

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Project description:BackgroundHost-derived (LL-37) and synthetic (WLBU-2) cationic antimicrobial peptides (CAPs) are known for their membrane-active bactericidal properties. LL-37 is an important mediator for immunomodulation, while the mechanism of action of WLBU-2 remains unclear.ObjectiveTo determine if WLBU-2 induces an early proinflammatory response that facilitates bacterial clearance in cystic fibrosis (CF).MethodsC57BL6 mice were given intranasal or intraperitoneal 1×10 (6) cfu/mL Pseudomonas aeruginosa (PA) and observed for 2h, followed by instillation of LL-37 or WLBU-2 (2-4mg/kg) with subsequent tissue collection at 24h for determination of bacterial colony counts and quantitative RT-PCR measurement of cytokine transcripts. CF airway epithelial cells (IB3-1, ?F508/W1282X) were cultured in appropriate media with supplements. WLBU-2 (25?M) was added to the media with RT-PCR measurement of TNF-? and IL-1? transcripts after 20, 30, and 60min. Flow cytometry was used to determine if WLBU-2 assists in cellular uptake of Alexa 488-labeled LPS.ResultsIn murine lung exposed to intranasal or intraperitoneal WLBU-2, there was a reduction in the number of surviving PA colonies compared to controls. Murine lung exposed to intraperitoneal WLBU-2 showed fewer PA colonies compared to LL-37. After 24h WLBU-2 exposure, PA-induced IL-1? transcripts from lungs showed a twofold decrease (p<0.05), while TNF-? levels were unchanged. LL-37 did not significantly change transcript levels. In IB3-1 cells, WLBU-2 exposure resulted in increased TNF-? and IL-1? transcripts that decreased by 60min. WLBU-2 treatment of IB3-1 cells displayed increased LPS uptake, suggesting a potential role for CAPs in inducing protective proinflammatory responses. Taken together, the cytokine response, LPS uptake, and established antimicrobial activity of WLBU-2 demonstrate its ability to modulate proinflammatory signaling as a protective mechanism to clear infection.ConclusionsThe immunomodulatory properties of WLBU-2 reveal a potential mechanism of its broad-spectrum antibacterial activity and warrant further preclinical evaluation to study bacterial clearance and rescue of chronic inflammation.

Dataset Information

Molecular basis of resistance to muramidase and cationic antimicrobial peptide activity of lysozyme in staphylococci.

Publications

Molecular basis of resistance to muramidase and cationic antimicrobial peptide activity of lysozyme in staphylococci.

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