Global genomic characteristics of mobile colistin resistance mcr genes in Enterobacterales from companion animals.

Abstract

Mobile colistin resistance (mcr) genes, initially described in livestock and humans, remain less frequently reported in companion animals. We conducted a global genomic survey of 14,643 bacterial genomes retrieved from the NCBI National Database of Antibiotic Resistant Organisms and identified 105 (0.7%) mcr-positive Enterobacterales from dogs (79.0%) and cats (21.0%). Escherichia coli (73.3%) and the Enterobacter cloacae complex (20.9%) predominated, with the mcr-1 and mcr-9 variants being the most frequent. Most genomes originated from Asia, Europe, and North America, reflecting the uneven geographic distribution of sequenced mcr-positive strains. Genomic analysis revealed a genetic plurality and co-occurrence of mcr genes with CTX-M-type extended-spectrum β-lactamases (46.6%), carbapenemases (5.7%), and 16S rRNA methyltransferases (8.6%), particularly in international high-risk clones. These findings underscore the diversity and epidemiological relevance of mcr-positive bacteria in pets, reinforcing the need for closer monitoring through One Health-based surveillance.