Prevalence and diversity of Salmonella spp., Campylobacter spp., and Listeria monocytogenes in two free-range pig slaughterhouses

Salmonella spp., Campylobacter spp. and Listeria monocytogenes have a significant impact on public health with slaughterhouses providing many opportunities for the proliferation of pathogenic bacteria. To evaluate the prevalence and diversity of these microorganisms along the free-range pork production chain, a total of 750 samples (5 samples/animal; 15 animals/farm; 5 farms/slaughterhouse) were collected from two slaughterhouses and analysed by specific ISO methodologies. Salmonella spp. (12.93%, CI95 10.72-15.52%), Campylobacter spp. (17.17%, CI95 13.00-21.74%) and L. monocytogenes (9.07%, CI95 7.21-11.33%) were recovered at different stages of the production chain, with the highest prevalence detected in tonsils for Salmonella spp. (30.67%, CI95 23.85-38.44%) and L. monocytogenes (39.33%, CI95 31.87-47.32%) and in faeces for Campylobacter spp. (57.33%, CI95 49.33-64.96%). Thirteen different Salmonella serotypes were detected with monophasic Salmonella Typhimurium as the most frequent one. C. coli, C. jejuni and L. monocytogenes serotype 4b and 1/2a were also identified. A significant higher prevalence of Salmonella spp. in total and from skin samples in slaughterhouse B than in slaughterhouse A was detected. In addition, a higher, although not significant, prevalence of the selected pathogens was observed in meat samples from slaughterhouse B with respect to slaughterhouse A (10.67% vs 0% for Campylobacter spp.; and 4% vs 0% for Salmonella spp. and L. monocytogenes). Our results highlight the risk of contamination of pork meat by the microorganisms under study and point out the importance of implementing specific control measures.