A small study of Yersinia enterocolitica in pigs from birth to carcass and characterisation of porcine and human strains

The objectives of this study were to investigate the present of Yersinia enterocolitica at the different stages of production from birth to chilled carcasses; to characterise the isolates in terms of bioserotype, virulence factors (ail, ystA, ystB, inv, yadA and virF) and antibiotic resistance profiles and to examine strains causing diarrheal illness in Ireland. Rectal, throat, floor, partition, wall and/or carcass swabs and water samples were testing for Y. enterocolitica using the bacteriological analytical method. Presumptive positive isolates were confirmed using API 20E strips. The isolates were then combined with 10 clinical strains, biotyped, serotyped, their antibiotic resistance phenotypes determined by disc diffusion and tested for the presence of ail, ystA, ystB, inv, yadA and virF genes using multiplex PCR assays. Y. enterocolitica had an overall prevalence rate of 0.55% (4/726). Y. enterocolitica 2/O:9 and 1A/O:9 were detected on the farm and/or in the abattoir. The clinical isolates were 1A/O:5, 1A/O:8, 1A/O:9, 2/O:9 or 4/O:9. All biotype 1A strains were ail, ystA, yadA and virF negative but carried the ystB gene. All biotype 2 and 4 strains were ail, ystA, yadA and virF positive. Resistant to cephalothin, ampicillin and amoxicillin/clavulanic acid was common and one 2/O:9 strain was resistant to compound sulphonamides and tetracycline. Intermediate resistance to neomycin and streptomycin was also observed. The data presented may explain the low incidence of yersiniosis in Ireland and suggests that biotype 1A may present a public health risk. Neomycin and tetracycline resistance have rarely been reported in Y. enterocolitica and should be monitored in future surveillance studies.