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Differences in recovery of Salmonella on pig carcasses using non-destructive and destructive sampling methods is not well understood in respect to the chilling processes applied in slaughterhouses. Therefore, in two slaughterhouses, four strains at two different concentrations were inoculated onto pork skin. Inoculated skin samples were sampled before and after chilling with two sampling methods: swabbing and destruction. Both slaughterhouses were visited three times and all tests were performed in triplicate. All samples were analysed using the ISO-method and recovered isolates were confirmed by PFGE. The chilling system (fast or conventional cooling) nor the sampling step (before and after chilling) did not significantly influence the recovery of Salmonella. However, swabbing after chilling leads to an underestimation of the real number of contaminated carcasses. Therefore, destructive sampling is the more designated sampling method after chilling.

Pigs are the main reservoir of human pathogenic Y. enterocolitica , and the microbiological and serological prevalence of this pathogen differs between pig farms. The infection status of pig batches at moment of slaughter is unknown while it is a possibility to classify batches. A relation between the presence of human pathogenic Yersinia spp. and the presence of antibodies could help to predict the infection of the pigs prior to slaughter. Pigs from 100 different batches were sampled. Tonsils and pieces of diaphragm were collected from 7047 pigs (on average 70 pigs per batch). The tonsils were analyzed using a direct plating method and the meat juice collected from the pieces of diaphragm was analyzed by Enzyme Linked ImmunoSorbent Assay. The microbiological and serological results were compared using a mixed-effects logistic regression at pig and batch level. Yersinia spp . were found in 2031 (28.8%) pigs, antibodies were present in 4692 (66.6%) pigs. According to the logistic regression, there was no relation at pig level between the presence of Yersinia spp. in tonsils and the presence of antibodies. Contrarily, at batch level, a mean activity value of 37 Optical Density (OD)% indicated a Yersinia spp. positive farm and the microbiological prevalence in pig batches could be estimated before shipment to the slaughterhouse. This offers the opportunity to classify batches based on their potential risk to contaminate carcasses with human pathogenic Yersinia spp.

Yersiniosis is the third most common of bacterial zoonosis in the EU. The main source for human infection is pork contaminated with human pathogenic Yersinia enterocolitica , for which pigs are the primary reservoir. The aim of this study was to acquire data about the distribution of the prevalence of human pathogenic Y. enterocolitica in different batches of slaughter pigs. Between August and October 2011, in five Belgian slaughterhouses tonsils of 1397 fattening pigs, originating from 66 batches, were collected. Samples were plated onto cefsulodin-irgasan-novobiocin agar plates and suspect Yersinia colonies were enumerated. Y. enterocolitica were found in 375 pig tonsils (26.8%), originating from 46 batches. The within-batch prevalence showed a large variation between the different batches and ranged from 0 to 83.3%. In 20 batches (30.3%), no positive tonsils were detected. The average number of Y. enterocolitica was 4.04 ± 0.97 log 10 CFU g −1 tonsillar tissue and the mean Yersinia count per batch varied between 3.08 and 5.89 log 10 CFU g −1 . In conclusion, human pathogenic Y. enterocolitica is widespread among Belgian pig farms, but there is a large variation in the within-batch prevalence among farms.