A new study is reported which was carried out to determine whether exposure of Salmonella to various biocides could act as a driver of antibiotic resistance. Salmonella enterica serovar Typhimurium was exposed to four biocides with differing modes of action. All antibiotic-resistant mutants were characterized phenotypically and genotypically to identify mechanisms of resistance. All biocides tested selected multidrug resistant (MDR) mutants with decreased antibiotic susceptibility; these occurred randomly throughout the experiments. Mutations that resulted in de-repression of the multidrug efflux pump AcrAB-TolC were seen in MDR mutants. A novel mutation in rpoA was also selected and contributed to the MDR phenotype. Other mutants were highly resistant to both quinolone antibiotics and the biocide triclosan. The authors concluded that exposure of bacteria to sub optimal concentrations of biocides can select for antibiotic-resistant mutants and this is mediated by clinically relevant mechanisms of resistance prevalent in human pathogens.
The study can be found at J Antimicrob Chemother 2015; doi:10.1093/jac/dkv109