jin, W. Y.; wei, S. D.; zhong, X. Z.; an, J. X.; xiang, c.

Plasmid-mediated quinolone resistance (PMQR) genes and mobile colistin resistance (MCR) genes in Escherichia coli (E. coli) have shown an increasing prevalence in recent years. This rise is particularly notable in China and several Southeast Asian countries, representing a significant threat to public health. In the present study, we conducted a retrospective analysis of MCR genes (mcr-1, mcr-2, mcr-3, mcr-4, and mcr-5) and PMQR genes (qnrA, qnrB, qnrC, qnrD, qnrE1, qnrVC, qnrS, aac(6\')-Ib-cr, qepA, and oqxAB). From the 3,663 E. coli isolates examined, 1,613 (44.0%) tested positive for PMQR genes, either individually or in combination. Meanwhile, 262 isolates (7.0%) carried MCR genes. Minimum inhibitory concentration (MIC) analyses of 17 antibiotics for the MCR gene-carrying strains revealed universal multidrug resistance. Resistance to polymyxin varied between 4 g/mL and 64 g/mL, with MIC50 and MIC90 values at 8 g/mL and 16 g/mL, respectively. Additionally, fluctuations in the detection rates of these resistant genes correlated with the introduction of antibiotic policies, host origin, temporal trends, and geographical distribution.