MRSA becoming resistant to household cleaners

Link: HighWire Press -- Medline Abstract.

To characterize mutants of Staphylococcus aureus expressing reduced susceptibility to house cleaners (HC), assess the impact of the alternative sigma factor SigB on HC susceptibility, and determine the MIC of clinical methicillin-resistant S. aureus (MRSA) to a HC. Methods and Results: Susceptibility to HC, HC components, H(2)O(2), vancomycin and oxacillin and physiological parameters were determined for HC-reduced susceptibility (HC(RS)) mutants, parent strain COL and COLsigB::kan. HC(RS) mutants selected with three HC expressed reduced susceptibility to multiple HC, HC components, H(2)O(2) and vancomycin. Two unique HC(RS) mutants also lost the methicillin resistance determinant. In addition, all HC(RS) mutants exhibited better growth at two temperatures, and one HC(RS) mutant expressed reduced carotenoid production. COLsigB::kan demonstrated increased susceptibility to all HC and many HC components. sigB operon mutations were not detected in one HC(RS) mutant background. Of 76 clinical MRSA, 20 exhibited reduced susceptibility to a HC. Conclusions: HC(RS) mutants demonstrate altered susceptibility to multiple antimicrobials. While sigB is required for full HC resistance, one HC(RS) mechanism does not involve sigB operon mutations. Clinical MRSA expressing reduced susceptibility to a common HC were detected. Significance and Impact of the Study: This study suggests that HC(RS) mutants are not protected against, nor selected by, practical HC concentrations.