Occurence of the mcr colistin resistance genes in extended-spectrum beta-lactamase-producing Escherichia coli from fish samples

Abstract

Antimicrobial resistance against colistin has emerged worldwide and is threatening the efficacy of colistin treatment of multi-resistance Gramnegative bacteria. Recent studies recorded that extended-spectrum betalactamase-producing Escherichia coli (ESBL producing E. coli) isolates existed in striped catfish, red tilapia and wild fish in the Mekong Delta, Vietnam. Therefore, the study is aimed to investigate the presence of mcr resistance genes (mcr-1, 3) in the ESBL producing E. coli isolates. A total of 88 ESBL-producing E. coli isolates were used in this study. These strains were isolated from cultured fish (striped catfish and red tilapia) and wild fish samples (unidentified species) collected from Vinh Long, Dong Thap and An Giang provinces. The PCR assays were carried out in a 25 µl reaction mixture. The PCR conditions of mcr genes consist of initial enaturing at 95ºC for 5 min, followed by 33 cycles of 95ºC for 30s; 58ºC for 90s; 72ºC for 30s, and a final extension step at 68ºC for 10 min. The results showed that there is the existence of mcr colistin resistance genes in ESBL-producing E. coli isolated from striped catfish in the Mekong delta at very low frequency. The results implied that there is a need for the surveillance and control programs for prevention of further spreading of colistin resistance genes.