Characterization of the Staphylococcus epidermidis accessory-gene regulator response: quorum-sensing regulation of resistance to human innate host defense.

Staphylococci are important opportunistic pathogens. However, there is a lack of information on how these bacteria survive inside the human body during infection. This study demonstrates that quorum-sensing regulation in Staphylococcus epidermidis protects it from key mechanisms of human innate host defense. To gain a better understanding of the basis of the observed phenotype, the agr quorum-sensing regulon of S. epidermidis was characterized by a genomewide analysis of gene expression. The gene-expression data indicate that agr adapts bacterial physiology to stationary growth and, furthermore, that it controls a series of virulence factors, including degradative exoenzymes possibly involved in resistance to antimicrobial peptides. Remarkably, agr also regulates general and oxidative stress-response factors, including detoxifying enzymes of reactive oxygen species. Taken together, the results of this study indicate that quorum-sensing regulation in staphylococci has important, previously unknown functions that contribute to protection from mechanisms of human innate host defense--and, therefore, to the pathogen's survival in the human host.