Comparative Genome Analysis of Livestock and Human Colistin-Resistant Escherichia coli Isolates from the Same Household

Abstract

Background Emergence and dissemination of colistin-resistant bacteria that harbor mobile colistin resistance ( mcr ) genes pose a dire challenge for the treatment of intractable infections caused by multidrug-resistant bacteria. Current findings on colistin-resistant bacteria in both humans and livestock of the same households highlight the need to identify the dissemination mechanisms of colistin-resistant bacteria. Methods In this study, a comparative genome analysis of colistin-resistant Escherichia coli isolates from livestock and humans of the same household was performed to clarify the possible dissemination mechanism of mcr genes among bacteria. Pulsed-field gel electrophoresis and whole-genome sequencing followed by sequence typing of the isolates were performed for assessment of the samples. Results The study revealed that two colistin-resistant E. coli isolates, one each from a pig and a chicken, were phylogenetically similar but not identical to the human isolates obtained from the same household. The comparative genome analysis revealed that the chicken isolate and a human isolate shared the same IncHl2 plasmid harboring the mcr transposon ( mcr-1 -PAP2). The pig isolate and the other human isolate retained the mcr-1 transposon on the chromosome, with the pig isolate carrying the complete mcr transposon (IS Apl1-mcr-1-PAP2 -IS Apl1 ) and the human isolate carrying the incomplete mcr transposon (IS Apl1-mcr-1-PAP2 ). Conclusion The results of the study confirm the distribution of colistin-resistant bacteria and subsequent transmission of the resistance gene-carrying transposon between livestock and humans of the same household. To the best of our knowledge, this is the first report on genomic analysis of colistin-resistant E. coli isolates obtained from livestock and residents of the same household.

Horizontal transfer of a plasmid possessing mcr-1 marked with a single nucleotide mutation between Escherichia coli isolates from community residents

“…The wide dissemination of colistin-resistant (COR) Enterobacteriaceae with a mobile colistin resistance gene, mcr , has been reported worldwide, especially in some Asian countries [ 1 – 3 ]. COR bacteria can spread to humans from livestock and animal foods [ 4 , 5 ]; additionally, a horizontal transfer of plasmids with mcr has been reported as an important theoretical mechanism in microbial communities [ 6 ]. However, demonstration of horizontal gene transfer requires the identification of plasmids with the same mcr in strains isolated from different sources.…”