Coresistance to quaternary ammonium compounds in extended-spectrum beta-lactamase-producing Escherichia coli

Background and Aim: Extended-spectrum β-lactamases (ESBL) in Escherichia coli constitutes one of the major threats to modern medicine, and the increasing pollution with quaternary ammonium compounds (QACs) has been suspected to contribute to the spread of ESBL-producing bacteria. The aim of the study was to investigate ESBLA and ESBLM-C-producing E. coli isolates for their coresistance to QACs and their phylogeny isolated from a Swedish University Hospital. Materials and Methods: Coresistance in E. coli with production of ESBL enzymes of the type blaCTX-M (n=23) was compared to E. coli producing AmpC type ESBL enzymes blaCMY and blaDHA (n=27). All isolates were tested for susceptibility to antibiotics and QACs, and high-quality whole-genome sequences were analyzed for resistance determinants. Results: The plasmid-borne small multidrug resistance (SMR) efflux pump sugE(p) was solely present in blaCMY-producing E. coli (n=9), within the same genetic environment blaCMY–blc–sugE(p). Other small multidrug efflux pumps were found without association for ESBL-types: emrE (n=5) and the truncated qacEΔ1 (n=18). Conclusion: Coresistance of ESBL enzymes and SMR efflux pumps in E. coli was common and might indicate that other substances than antibiotics contribute to the spread and emergence of antibiotic resistance.