Genomic Comparison of Campylobacter spp. and Their Potential for Zoonotic Transmission between Birds, Primates, and Livestock

Campylobacter is the leading cause of human gastroenteritis worldwide. Wild birds, including American crows, are abundant in urban, suburban, and agricultural settings and are likely zoonotic vectors ofCampylobacter . Their proximity to humans and livestock increases the potential spreading ofCampylobacter via crows between the environment, livestock, and humans. However, no studies have definitively demonstrated that crows are a vector for pathogenicCampylobacter . We used genomics to evaluate the zoonotic and pathogenic potential ofCampylobacter from crows to other animals with 184 isolates obtained from crows, chickens, cows, sheep, goats, humans, and nonhuman primates. Whole-genome analysis uncovered two distinct clades ofCampylobacter jejuni genotypes; the first contained genotypes found only in crows, while a second genotype contained “generalist” genomes that were isolated from multiple host species, including isolates implicated in human disease, primate gastroenteritis, and livestock abortion. Two major β-lactamase genes were observed frequently in these genomes (oxa-184 , 55%, andoxa-61 , 29%), whereoxa-184 was associated only with crows andoxa-61 was associated with generalists. Mutations ingyrA , indicative of fluoroquinolone resistance, were observed in 14% of the isolates. Tetracycline resistance (tetO ) was present in 22% of the isolates, yet it occurred in 91% of the abortion isolates. Virulence genes were distributed throughout the genomes; however,cdtC alleles recapitulated the crow-only and generalist clades. A specificcdtC allele was associated with abortion in livestock and was concomitant withtetO . These findings indicate that crows harboring a generalistC. jejuni genotype may act as a vector for the zoonotic transmission ofCampylobacter .IMPORTANCE This study examined the link between public health and the genomic variation ofCampylobacter in relation to disease in humans, primates, and livestock. Use of large-scale whole-genome sequencing enabled population-level assessment to find new genes that are linked to livestock disease. With 184Campylobacter genomes, we assessed virulence traits, antibiotic resistance susceptibility, and the potential for zoonotic transfer to observe that there is a “generalist” genotype that may move between host species.