Rui Tian, Mengqi Yang, Yujie Yang, Shuqin Xu, Wanzhao Chen, Lining Xia
(10.5%) showed lower prevalence. The overall detection rate of mcr genes (mcr-1 to mcr-9) was low (0.5%). ESBL-producing isolates were identified in 9.8% (n = 40) of the total strains, indicating the presence of extended-spectrum β-lactamase-mediated resistance mechanisms. Importantly, two mcr-8.2 positive isolates were detected, one of which belonged to the ST147 clone. The backbone structure of the mcr-8.2 positive IncFII plasmid (pCD19-mcr8) identified in this study shared high structural similarity with known mcr-8.2-positive plasmids from chicken, human, and environmental sources. The mcr-8.2 core genetic environment (IS903B-dgkA-baeS-copR-ISEcl1-mcr-8.2-ISKpn26) also found in these plasmids. In addition, transfer of the IncFII plasmid pCD19-mcr8 into E. coli did not result in a significant fitness cost. To our knowledge, this is the first report of mcr-8.2-positive K. pneumoniae in layer chickens in Xinjiang, China. These findings highlight the contribution by mobile genetic elements (MGEs) to cross-species dissemination of colistin resistance and emphasize the necessity of a One Health strategy for monitoring and controlling such pathogens and AMR.