VraT/YvqF Is Required for Methicillin Resistance and Activation of the VraSR Regulon in Staphylococcus aureus

Abstract

ABSTRACTStaphylococcus aureusinfections caused by strains that are resistant to all forms of penicillin, so-called methicillin-resistantS. aureus(MRSA) strains, have become common. One strategy to counter MRSA infections is to use compounds that resensitize MRSA to methicillin.S. aureusresponds to diverse classes of cell wall-inhibitory antibiotics, like methicillin, using the two-component regulatory system VraSR (vra) to up- or downregulate a set of genes (the cell wall stimulon) that presumably facilitates resistance to these antibiotics. Accordingly, VraS and VraR mutations decrease resistance to methicillin, vancomycin, and daptomycin cell wall antimicrobials.vraSandvraRare encoded together on a transcript downstream of two other genes, which we callvraUandvraT(previously calledyvqF). By producing nonpolar deletions invraUandvraTin a USA300 MRSA clinical isolate, we demonstrate thatvraTis essential for optimal expression of methicillin resistancein vitro, whereasvraUis not required for this phenotype. The deletion ofvraTalso improved the outcomes of oxacillin therapy in mouse models of lung and skin infection. SincevraTexpressed intransdid not complement avraoperon deletion, we conclude that VraT does not inactivate the antimicrobial. Genome-wide transcriptional microarray experiments reveal that VraT facilitates resistance by playing a necessary regulatory role in the VraSR-mediated cell wall stimulon. Our data prove that VraTSR comprise a novel three-component regulatory system required to facilitate resistance to cell wall agents inS. aureus. We also provide the firstin vivoproof of principle for using VraT as a sole target to resensitize MRSA to β-lactams.