Colistin resistance prevalence in Escherichia coli from domestic animals in intensive breeding farms of Jiangsu Province.

The global dissemination of colistin resistance has received a great deal of attention. Recently, the plasmid-mediated colistin resistance encoded by mcr genes in Escherichia coli (E. coli) strains from animals, food, and patients in China has been reported frequently. To investigate the colistin resistance and mcr-1 and mcr-2 genes spread in domestic animals in Jiangsu Province, we collected fecael swabs from pigs, chicken and cattle at different ages distributed in intensive feeding farms. The selective chromogenic agar and mcr-PCR were used to screen the colistin resistance and mcr gene carriage. Colistin resistant E. coli colonies were identified in 54.25% (440/811), 35.96% (443/1232), and 26.92% (42/156) faecal swabs from pigs, chickens, and cattle, respectively. The prevalence of mcr-1 in colistin resistant E. coli isolates from pigs, chickens and cattle was 68.86% (303/440), 87.58% (388/443), and 71.43% (30/42), respectively, compared to mcr-2 which was present in 46.82% (206/440), 14.90% (66/443), and 19.05% (8/42) of the colistin-resistant E. coli isolated from pigs, chickens and cattle, respectively. Co-occurrence of mcr-1 and mcr-2 was identified in 20% (88/440) in pigs, 7.22% (32/443) in chickens, and 9.52% (4/42) in cattle. Interventions and alternative options are necessary to minimise further dissemination of mcr between food-producing animals and human.