Yu-Ping Cao, Qing-Qing Lin, Wan-Yun He, Jing Wang, Meng-Ying Yi, Lu-Chao Lv, Jun Yang, Jian-Hua Liu, Jian-Ying Guo. 2020. Co-selection may explain the unexpectedly high prevalence of plasmid-mediated colistin resistance gene mcr-1 in a Chinese broiler farm. Zoological Research, 41(5): 569-575. DOI: 10.24272/j.issn.2095-8137.2020.131
Citation: Yu-Ping Cao, Qing-Qing Lin, Wan-Yun He, Jing Wang, Meng-Ying Yi, Lu-Chao Lv, Jun Yang, Jian-Hua Liu, Jian-Ying Guo. 2020. Co-selection may explain the unexpectedly high prevalence of plasmid-mediated colistin resistance gene mcr-1 in a Chinese broiler farm. Zoological Research, 41(5): 569-575. DOI: 10.24272/j.issn.2095-8137.2020.131

Co-selection may explain the unexpectedly high prevalence of plasmid-mediated colistin resistance gene mcr-1 in a Chinese broiler farm

  • The rise of the plasmid-encoded colistin resistance gene mcr-1 is a major concern globally. Here, during a routine surveillance, an unexpectedly high prevalence of Escherichia coli with reduced susceptibility to colistin (69.9%) was observed in a Chinese broiler farm. Fifty-three (63.9%) E. coli isolates were positive for mcr-1. All identified mcr-1-positive E. coli (MCREC) were multidrug resistant and carried other clinically significant resistance genes. Furthermore, the mcr-1 genes were mainly located on the IncI2 and IncHI2 plasmids. Conjugation experiments unraveled the co-transfer of mcr-1 with other antibiotic resistance genes (blaCTX-M-55, blaCTX-M-14, floR, and fosA3) via the IncI2 (n=3) and IncHI2 (n=4) plasmids. The stable genetic context mcr-1-pap2 was common in the IncI2 plasmids, whereas ISApl1-mcr-1-pap2-ISApl1 was mainly found in the IncHI2 plasmids. The dominance of mcr-1-bearing IncI2 and IncHI2 plasmids and co-selection of mcr-1 with other antimicrobial resistance genes might contribute to the exceptionally high prevalence of mcr-1 in this broiler farm. Our results emphasized the importance of appropriate antibiotic use in animal production.
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