Genomic Characterization of Two Isolates Harboring Gene From Farm Environment.

The prevalence and transmission of mobile colistin resistance () genes have led to a severe threat to humans and animals. is an emerging pathogen which is closely related to a variety of diseases. However, the report of genes harboring is still rare. One study in Brazil reported the isolates with IncHI2-type plasmids harboring . A Chinese study reported two strains carrying gene with the same plasmid type IncI2. Here, we identified two strains of carrying gene from farm environments with IncX4-type and IncI2-type plasmids, respectively. To our best knowledge, this is the first report about gene located on IncX4-type plasmid in . We investigate the resistance mechanism of colistin-resistant strains 6S41-1 and 5ZF15-2-1 and elucidate the genetic context of plasmids carrying genes. In addition, we also investigated chromosomal mutations mediated colistin resistance in these two strains. Species identification was performed using MALDI-TOF MS and 16S rRNA gene sequencing. The detection of gene was determined by PCR and Sanger sequencing. S1-pulsed-field gel electrophoresis (PFGE), Southern blotting, antimicrobial susceptibility testing, conjugation experiments, complete genome sequencing, and core genome analysis were conducted to investigate the characteristics of isolates harboring . The genes on two strains were both plasmids encoded and the typical IS--- cassette was identified in p6S41-1 while a -- locus sites on the conjugative plasmid p5ZF15-2-1. In addition, Core genome analysis reveals that 6S41-1 and 5ZF15-2-1 have close genetic relationships. The gene is located on conjugative IncI2-type plasmid p5ZF15-2-1, which provides support for its further transmission. In addition, there's the possibility of spreading to humans through farm environments and thereby threatening public health. Therefore, continuous monitoring and investigations of among in farm environments are necessary to control the spread.