Parallel evolutionary pathways to antibiotic resistance selected by biocide exposure
Journal of Antimicrobial Chemotherapy August 2015 V.70 N.8 P.2241-2248
Mark A. Webber, Rebekah N. Whitehead, Manuella Mount, Nick J. Loman, Mark J. Pallen, and Laura J. V. Piddock
1Antimicrobials Research Group, School of Immunity and Infection and Institute for Microbiology and Infection, College of Medical and Dental Sciences, University of Birmingham, Birmingham B15 2TT, UK
2School of Bioscience and Institute for Microbiology & Infection, College of Life and Environmental Sciences, University of Birmingham, Birmingham B15 2TT, UK
3Division of Microbiology and Infection, Warwick Medical School, University of Warwick, Coventry CV4 7AL, UK
*Corresponding author. Tel: +0121-414-2859; E-mail: email@example.com
Biocides are widely used to prevent infection. We aimed 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. Antibiotic-resistant mutants were selected during exposure to all biocides and characterized phenotypically and genotypically to identify mechanisms of resistance.
All biocides tested selected 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.
This study shows that exposure of bacteria to biocides can select for antibiotic-resistant mutants and this is mediated by clinically relevant mechanisms of resistance prevalent in human pathogens.