Genomic characterization of carbapenem and colistin-resistant isolates from humans and dogs.

Introduction: Carbapenem and colistin-resistant , including , have become a growing global concern, posing a significant threat to public health. Currently, there is limited information about the genetic background of carbapenem and colistin-resistant isolates infecting humans and dogs in Thailand. This study aimed to characterize carbapenem and colistin-resistant genes in six resistant clinical isolates (three from humans and three from dogs) which differed in their pulse field gel electrophoresis profiles.

Methods: Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS), antimicrobial susceptibility testing, and whole-genome sequencing were employed to identify and analyze the isolates.

Results And Discussion: All six isolates were carbapenemase-producing isolates with chromosomally carried and genes, as well as nine to 21 virulence genes. The isolates belonged to five multilocus sequence types (STs): one isolate from a human and one from a dog belonged to ST16, with the other two human isolates being from ST340 and ST1269 and the other two dog isolates were ST147 and ST15. One human isolate and two dog isolates harbored the same gene on the ColKP3 plasmid, and one dog isolate carried the gene on the IncFII plasmid. Notably, one human isolate exhibited resistance to colistin mediated by the gene carried on the IncFII plasmid, which co-existed with resistance determinants to other antibiotics, including aminoglycosides and quinolones. In conclusion, this study provides a comprehensive characterization of both chromosome- and plasmid-mediated carbapenem and colistin resistance in a set of clinical isolates from unrelated humans and dogs in Thailand. The similarities and differences found contribute to our understanding of the potential widescale dissemination of these important resistance genes among clinical isolates from humans and animals, which in turn may contribute to outbreaks of emerging resistant clones in hospital settings.