Campylobacter jejuni subsp. jejuni isolates from American black bear (Ursus americanus). Campylobacter jejuni subsp. jejuni

The Gram-negative bacterium Campylobacter jejuni is part of the commensal gut microbiota of numerous animal species and a leading cause of bacterial foodborne illness in humans. Most complete genomes of C. jejuni are from strains isolated from human clinical samples, poultry, and ruminants. Recently, there has been an increased interest in sequencing isolates from wildlife to determine if such hosts are possible sources or vectors for the spread of C. jejuni. The aim of this study was to characterize and compare the complete genomes of nine C. jejuni isolates from wild American black bears living in the southeastern United States to other complete C. jejuni genomes isolated from other sources. The panel proved markedly diverse, with eight multilocus sequence types and seven lipooligosaccharide (LOS) biosynthesis locus classes identified among the nine isolates. Average nucleotide identity (ANI), genome alignments and pan-genome analyses indicated that seven of the strains had >97% similarity to each other and to C. jejuni subsp. jejuni while two strains had <97% similarity to C. jejuni subsp. jejuni and <96% similarity to C. jejuni subsp. doylei. Phylogenetic analysis of all the genomes distinguishes these two bear isolates clustering them between C. jejuni subsp. jejuni and C. jejuni subsp. doylei. Like certain strains of C. jejuni subsp. doylei, both bear isolates possess the Entner-Doudoroff (ED) pathway and a deletion within the cytolethal distending toxin genes, cdtABC. The data provide initial evidence that black bears, as omnivores, may act as a generalist host, but may also support bear-specific C. jejuni.