Prevalence and characterization of Salmonella spp. and Campylobacter spp. in slaughter sheep

At two Swiss abattoirs, 653 caecum samples from slaughtered sheep were examined. The aim of the study was (i) to determine the prevalence of Salmonella spp. and Campylobacter spp., (ii) to further characterize isolated strains, (iii) and to discuss the results obtained with their relevance to food safety. 11 % of the samples were Salmonella spp. positive and 17.5 % Campylobacter spp. positive. All isolated Salmonella were identified as S. enterica subsp. diarizonae serovar 61:k:1,5,(7) and further genotyped by pulsed-field gel electrophoresis (PFGE) and ribotyping. PFGE showed 22 different profiles and proved to have greater discriminating power than ribotyping. Of the 114 isolated Campylobacter spp. strains, 64.9 % were shown to be C. jejuni and 35.1 % C. coli. In total, the susceptibility test yielded nine strains resistant to antibiotics: six strains were resistant against tetracycline, one against ciprofloxacin/nalidixic acid, one against ciprofloxacin/nalidixic acid and tetracycline, and one against streptomycin. In conclusion, sheep are a reservoir for pathogens of latent zoonoses as S. enterica subsp. diarizonae and Campylobacter spp. These pathogens may contaminate the carcasses during the slaughtering process. The maintenance of slaughter hygiene, which can be measured in daily practice by ,,slaughter-process-controls" and regular microbiological monitoring of carcasses as a verification system according to the HACCP principles, is consequently of central importance.