Phenotype Microarray characterization of biocides resistant Staphylococcus aureus strains

Resistance to antiseptics based on quaternary ammonium compounds (QACs) is widespread among clinical human bacterial isolates. Evidence suggests that extensive use of biocides may impose selective pressure contributing to the emergence of decreased antiseptic susceptibility and cross-resistance between widely used biocides and antibiotics. In Staphylococcus aureus, resistance to QACs is often associated to the presence of plasmid encoded efflux pumps known as QAC transporters. To study the responses associated to different QAC pumps and to identify new potential efflux targets, we analyzed by the Phenotype Microarray high-throughput technology the metabolic activity of 10 QAC+ strains of S. aureus in presence of 240 different toxic compounds, each one at 4 concentrations, in comparison with 5 QAC- strains. Beside the identification of known efflux targets, PM approach highlighted new potential targets for QAC pumps, that must be confirmed through MIC/MBC determination and efflux assays. The identification of new chemicals inducing lower tolerance correlating with the presence of QAC determinants opens new perspectives for the development of more effective antimicrobial treatments.