Molecular typing of isolates from pigs and farm environment based on and alleles.

The dissemination of polymyxin resistance represents a significant threat to public health. Sequence-based typing was performed by 53 isolates using / (CH) genes to characterize clones spreading from pig farming. Furthermore, 12 isolates had their whole genome sequenced for phylogenetic study. The isolates were classified into 22 distinct CH types, and two novel CH types (CH41-1578 and CH4-1579) and one sequence type (ST12652) was also described. According to phylogenetic study, both multilocus sequence typing and CH methods grouped the isolates similarly. Our findings suggest that the dissemination of the gene in pig farming has occurred mainly by horizontal gene transfer, and CH typing proved to be a good tool to characterize clones.