Comparison of gene expression profiles of uropathogenic Escherichia coli CFT073 after prolonged exposure to subinhibitory concentrations of different biocides

Biocides are chemical compounds widely used in hospital settings for a variety of purposes, but mainly for disinfection. The chemical properties of a biocide, as well as the biocide concentration, influence which cellular targets are affected. Exposure of bacteria to residual concentrations of biocides could lead to development of increased resistance towards the biocide in use, as well as cross-resistance towards other antimicrobials, including antibiotics. The aim of this study was to examine whether biocides could induce any potentially relevant genes that could affect pathogen's drug resistance or fitness. By examining global gene expression of the uropathogenic Escherichia coli CFT073 after exposure to subinhibitory concentrations of four biocides (benzalkonium chloride - BAC, chlorhexidine - CHX, hydrogen peroxide - H2O2, triclosan - TSN), we found that each biocide changed expression of different groups of genes and that exposure to benzalkonum chloride caused changes in expression of the largest number of genes among all biocides. In general, the four biocides tested in this study at subinhibitory concentrations did not increase the resistance potential of the pathogen to other antimicrobials. We could, however, identify clusters of genes that could possibly help the strain to grow in the presence of a biocide in the medium. A culture of E. coli CFT073 without any biocide treatment served as the control sample. That culture was grown under the exact same conditions as the four biocide-treated samples. Each sample was collected in three biological replicates at the mid-exponential phase of growth.