Occurrence of Yersinia enterocolitica and Campylobacter spp. in slaughter pigs and consequences for meat inspection, slaughtering, and dressing procedures

The purpose of the present investigation was to assess the occurrence of Yersinia enterocolitica and Campylobacter spp. in the lymphoid tissues and intestinal tract in pigs and the risk for contamination during the compulsory meat inspection procedures and the procedures during slaughtering and dressing. Another objective of the investigation was to compare traditional isolation methods, the use of a polymerase chain reaction (PCR) method (BUGS'n BEADS bacterial DNA isolation kit) and an ELISA method (VIDAS CAM) as tools in risk management in the slaughterhouse. The results indicate that the compulsory procedure for the incision of the submaxillary lymph nodes represents a cross-contamination risk for virulent Yersinia. In the screening of 97 animals in 1999, 5.2% of the samples were positive, and by the sampling of 24 samples in 2000-2001, 12.5% of the samples were positive. In the last case, Y. enterocolitica O:3 was found in the kidney region in one of the subsequent carcasses that was only touched by the meat inspection personnel before sampling. In addition, incision of the mesenteric lymph nodes might represent a cross-contamination risk since 8.3% of the samples were positive. The association between antibody titres and the occurrence of virulent yersiniae in the tonsils (21-18) was striking, with virulent yersiniae found in the tonsils in most pigs with high titres. The contents of the stomach, ileum, caecum, and colon also represent contamination risks for Y. enterocolitica O:3 if the slaughterhouse personnel cuts into the viscera with their knives by accident; the frequency of virulent Yersinia varied from 4.2% to 16.7% within these sections. Campylobacter was detected in the gastrointestinal tract of all pigs, and the high contamination of tonsils (66.7%) and intestinal tract (100%) might represent an occupational health hazard. There was no statistical difference between the traditional method for isolation of Y. enterocolitica [International Organization for Standardization, 1994. Microbiology-General Guidance for the Detection of Presumptive Pathogenic Yersinia enterocolitica (ISO 10273). International Organization for Standardization, Geneve, Switzerland (16 pp.)] and the BUGS'n BEADS detection method for virulent Y. enterocolitica. Likewise, there was no statistical difference between the traditional method for isolation of Campylobacter spp. [Nordic Committee on Food Analysis, 1990. Campylobacter jejuni/coli. Detection in Food. Method No. 119, 2nd ed. Nordic Committee on Food Analysis, Esbo (7 pp.)] and the BUGS'n BEADS detection method or the VIDAS CAM method for detection of Campylobacter spp.