Characterisation of Yersinia Enterocolitica Strains Isolated from Wildlife in the Northwestern Italian Alps.

Introduction: Yersiniosis is a zoonosis causing gastroenteritis, diarrhoea, and occasionally reactive arthritis and septicaemia. Cases are often linked to meat consumption and the most common aetiological agent is the Gram-negative bacilliform Yersinia enterocolitica bacterium. The occurrence of Yersinia spp. among wild animals has mostly been studied in wild boar, but it has seldom been in other species. Material and Methods: A total of 1,868 faecal samples from animals found dead or hunted were collected between 2015 and 2018 in the Valle d'Aosta region of the northwestern Italian Alps. Alpine ibex faecal samples were collected during a health monitoring program in 2018. Bacteria were isolated via PCR and confirmed as Y. enterocolitica biochemically. Strain antimicrobial susceptibility was tested by Kirby-Bauer disc diffusion, and the presence of virulence factors and antimicrobial resistance genes was investigated using whole-genome sequencing. Results: Yersinia enterocolitica strains of biotype 1A were detected in six faecal samples from red deer (0.93%), roe deer (0.49%) and red foxes (0.7%). Strains found in beech martens (3.57%) and Alpine ibex (2.77%) belonged to biotypes 1B and 5, respectively and harboured the pYPTS01 plasmid that had only been detected in Y. pseudotuberculosis PB1/+. All the isolates were resistant to ampicillin and erythromycin. Conclusion: The biovar 1A strains exhibited different virulence factors and behaved like non-pathogenic commensals. The strain from an Alpine ibex also harboured the self-transmissible pYE854 plasmid that can mobilise itself and the pYPTS01 plasmid to other strains. The beech marten could be considered a sentinel animal for Y. enterocolitica. Phenotypic resistance may account for the ability of all the strains to resist ß-lactams.

The diagnostic activity on wild animals through the description of a model case report (caseous lymphadenitis by Corynebacterium pseudotuberculosis associated with Pasteurella spp and parasites infection in an alpine ibex - Capra ibex).

The diagnostic activity on wild animals implies a hard laboratory protocol where multiple disciplines, from biology to pathological anatomy until the biotechnological techniques, must be integrated to establish the causes of death. To demonstrate these concepts, the analytical approach adopted for an alpine ibex (Capra ibex) found dead in a mountain area of North Western Italy was described. The animal showed sub-costal and lymph nodes collections of green-yellow pus, fibrinous pleuropneumonia and catarrhal-hemorrhagic enteritis. Purulent process was ascribed to Corynebacterium pseudotuberculosis, the causative agent of caseous lymphadenitis or pseudotuberculosis, pleuropneumonia to Pasteurella multocida and Mannheimia haemolytica and enteritis to Mannheimia haemolytica. Parasitic bronchopneumonia in the caudal lobes of the lung, a severe enteric infestation by gastro-intestinal and pulmonary strongyles and coccidia were found. The cause of death in the studied ibex appeared to be a consequence of an association between various pathological processes, with bacteriological and parasitic etiology.