Extended-spectrum β-lactamase-producing Escherichia coli with chromosomally integrated resistance genes isolated from a wild Asian black bear.

Carriage of antimicrobial-resistant bacteria in wildlife is a growing public health concern. We isolated an extended-spectrum β-lactamase-producing Escherichia coli from the feces of a wild bear collected in a persimmon orchard in 2025. The bear isolate exhibited resistance to ampicillin, cefazolin, cefotaxime, tetracycline, and chloramphenicol. Whole-genome sequencing revealed that the strain belonged to ST5044-OUT:H29 and harbored the blaCTX-M-55 and other resistance genes integrated into the bacterial genome. Comparative genomic analysis showed close relatedness to isolates from a Vietnamese pig farmer and a Japanese slaughterhouse wastewater, with pairwise distances of 0-80 single-nucleotide polymorphisms. DNA metabarcoding revealed a diet dominated by wild vegetation, with a minor anthropogenic plant component. Thus, wild bears may contribute to the dissemination of antimicrobial-resistant E. coli at the human-wildlife interface.