Prevalence of pathogenic Yersinia enterocolitica in pigs slaughtered at a Swiss abattoir.

Human yersiniosis is the third most common enteric disease after campylobacteriosis and salmonellosis in many European countries. However, epidemiological data on the prevalence of pathogenic Yersinia enterocolitica in animals and humans is insufficient. Pigs are assumed to be the main reservoir of pathogenic Y. enterocolitica because pig is so far the only animal species from which pathogenic strains have frequently been isolated. This work was conducted to study the frequency of ail-positive Y. enterocolitica in pigs slaughtered at a Swiss abattoir. In total, 212 pig tonsils were screened by real-time PCR and culture methods. The prevalence rate of ail-positive Y. enterocolitica in pigs at slaughter was 88% and 34% with PCR and culture methods, respectively. The 148 ail-positive isolates from the 72 culture-positive tonsils were bio-and serotyped. The most common bioserotype was 4/O:3 found in 96% (69/72) of the culture-positive samples. However, pig was also shown to be a reservoir for ail-positive Y. enterocolitica belonging to bioserotypes 2/O:5,27 and 2/O:9, which were detected in 8% (6/72) and 1% (1/72) of the culture-positive samples, respectively. Using PFGE with NotI, only a limited number of different patterns was found. In all, 6 genotypes were obtained when 86 isolates of bioserotype 4/O:3 from 69 samples were characterised and two genotypes (N1 and N4) dominated. The biotype 4 differs clearly from biotype 2 with PFGE. Antimicrobial resistance testing of 77 ail-positive Y. enterocolitica isolates from 72 samples studied with disc-diffusion revealed that all strains were sensitive to cefotaxime, chloramphenicol, ciprofloxacin and tetracycline, which are antimicrobial agents used for treatment of human disease. The isolates of bioserotype 2/O:5,27 differed from the isolates of bioserotypes 2/O:9 and 4/O:3 in resistance to ampicillin and amoxicillin/clavulanic acid.