The prevalence, characterisation, and antimicrobial resistance of Yersinia enterocolitica in pigs from Central Italy.

Widely spread in nature, Yersinia enterocolitica (YE) is a foodborne pathogen of major health and economic significance in developed countries. The aim of this study is to analyse YE strains isolated from 400 slaughtered pigs from the Abruzzo region, Italy, using biochemical tests and a multiplex polymerase chain reaction PCR detecting 6 chromosomal genes (ystA, irp2, 16s, ail, inv, hemR) and one plasmid-borne virulence gene (yadA). Antimicrobial susceptibility was evaluated and pulsed-field gel electrophoresis (PFGE) was also performed in order to assess phylogenetic diversity. In total, 56 samples of porcine tonsils (14%) were found to be positive for the presence of pathogenic YE. All YE belonged to the pathogenic bioserotype 4/O:3. All YE samples were positive for the chromosomal virulence genes ystA, ail, and inv, whereas results for the presence of yadA and hemR were variable. This study found that YE isolates were resistant to ampicillin (100%), streptomycin (26.79%), sulfisoxazole (19.65%), tetracycline (16.08%), nalidixic acid (14.30%), and chloramphenicol (10.72%). The strains characterised by PFGE showed a high similarity. This study demonstrates the usefulness of multiplex polymerase chain reaction (PCR) compared with conventional phenotypic assays for the identification of pathogenic YE isolates and the limitations of PFGE for the molecular typing of YE bioserotype 4/O:3.