Genetic Characterization of -Bearing Plasmids Harbored by Food-Borne Cephalosporin-Resistant Strains in China.

This study aims to investigate and compare the complete nucleotide sequences of the multidrug resistance plasmids pVb0267 and pVb0499, which were recovered from foodborne isolates, and analyze the genetic environment of to provide insight into the dissemination mechanisms of this resistance element. Analysis of the sequences of plasmids pVb0267 (166,467 bp) and pVb0499 (192,739 bp) revealed that the backbones of these two plasmids exhibited a high degree of similarity with pR148, a recognized type 1a IncC plasmid recovered from (99% identity). The resistance genes, found in both plasmids, included (A), and , which were mostly arranged in a specific region designated ARI-A. Plasmid pVb0499 was found to possess a larger size of ARI-A than pVb0267, which lacked a determination region, a A segment, an gene and several mobility-encoding genes. Comparative analysis of resistance island (RI) of these plasmids and others revealed the potential evolution route of these RI sequences. In conclusion, plasmids harboring the gene has been recovered in strains of food origin. It is alarming to find that IncC plasmids harboring resistance islands are disseminating in aquatic bacterial strains. The continuous evolution of resistance genes in conjugative plasmid in aquatic bacteria could be due to bacterial adaption to aquaculture environment, where antibiotics were increasingly used.