Illumina sequencing of Triclosan induced antibiotic resistant Escherichia coli K-12 MG1655. Escherichia coli K-12

Antibiotic resistance is a major threat to public health globally. It is generally recognized that the overuse and misuse of antibiotic induces antibiotic resistance. However, the potential role of emerging environmental contaminants in the dissemination of antibiotic resistance remains poor understood. In particular, it is unclear whether emerging contaminant triclosan (TCS, as a widely used biocide) directly cause antibiotic resistance through mutation, serving as a selection force. By combining experimental evolution under exposure of TCS with environmentally relevant concentrations, we found that TCS of 0.2 mg/L significantly increase mutation frequency and induce the development of multi−drug resistance (MGR) in Escherichia coli. DNA sequencing results identified key genetic mutations in fabI, frdD, marR, acrR and soxR genes in TCS selected mutant strains. Our findings implied the contribution of TCS to the dissemination of antibiotic resistance has been underestimated. These findings will enhance our understanding of the dissemination of antibiotic resistance in microbes induced by biocides and have implications for assessing the risks of TCS application.