Rural Raccoons (Procyon lotor) Not Likely to Be a Major Driver of Antimicrobial Resistant Human Salmonella Cases in Southern Ontario, Canada: A One Health Epidemiological Assessment Using Whole-Genome Sequence Data

Abstract

Non-typhoidal Salmonella infections represent a substantial burden of illness in humans, and the increasing prevalence of antimicrobial resistance among these infections is a growing concern. Using a combination of Salmonella isolate short-read whole-genome sequence data from select human cases, raccoons, livestock and environmental sources, and an epidemiological framework, our objective was to determine if there was evidence for potential transmission of Salmonella and associated antimicrobial resistance determinants between these different sources in the Grand River watershed in Ontario, Canada. Logistic regression models were used to assess the potential associations between source type and the presence of select resistance genes and plasmid incompatibility types. A total of 608 isolates were obtained from the following sources: humans (n = 58), raccoons (n = 92), livestock (n = 329), and environmental samples (n = 129). Resistance genes of public health importance, including blaCMY−2, were identified in humans, livestock, and environmental sources, but not in raccoons. Most resistance genes analyzed were significantly more likely to be identified in livestock and/or human isolates than in raccoon isolates. Based on a 3,002-loci core genome multi-locus sequence typing (cgMLST) scheme, human Salmonella isolates were often more similar to isolates from livestock and environmental sources, than with those from raccoons. Rare instances of serovars S. Heidelberg and S. Enteritidis in raccoons likely represent incidental infections and highlight possible acquisition and dissemination of predominantly poultry-associated Salmonella by raccoons within these ecosystems. Raccoon-predominant serovars were either not identified among human isolates (S. Agona, S. Thompson) or differed by more than 350 cgMLST loci (S. Newport). Collectively, our findings suggest that the rural population of raccoons on swine farms in the Grand River watershed are unlikely to be major contributors to antimicrobial resistant human Salmonella cases in this region.

Spread and mitigation of antimicrobial resistance at the wildlife-urban and wildlife-livestock interfaces

“…Raccoons are more liable to be net recipients of AMR than drivers when compared to human populations. 58 Thus, humans appear to pose more of an AMR threat to these wildlife populations than vice versa. However, work on wildlife zoonoses in Spain demonstrates that wildlife-to-human AMR risks are non-negligible and likely higher for wildlife that readily traverses into and throughout the built environment.…”

Ecology and epidemiology of Salmonella spp. isolated from the environment and the roles played by wild animals in their maintenance

“…Studies have shown a high occurrence of diverse Salmonella serovars belonging mostly to S. enterica [101]. Uncommon subspecies, S. enterica subspecies diarizonae 40:i: z 53, z54 and 48:k z57 have been reported in free-living adders and humans [101,102]. Salmonella shedding in snakes draws attention to possible zoonotic and epidemiological impacts, much more so in countries where snakes are handled, kept Available at www.onehealthjournal.org/Vol.9/No.1/1.pdf as pets and consumed by omnivorous animals, including man [101].…”

Prevalence of Salmonella spp. and Escherichia coli in the feces of free-roaming wildlife throughout South Korea

“…Salmonella spp. are found in the gastrointestinal tracts of both domestic [ 6 ] and wild animals [ 7 ], as well as in humans [ 8 ]. They are transmitted through feces into agricultural produce [ 9 ], particularly leafy vegetables, during irrigation, cultivation, and processing [ 10 ], and they can spread from one animal to another (domestic to wild and vice versa) and from one person to another.…”