Pheno and genotyping of Salmonella from slaughtered pigs in a Portuguese abattoir reveal differential persistence ability.

Pork is one of the most common vehicles of non-typhoid foodborne Salmonella, with the slaughterhouse representing a key point for the infection of pigs and carcass contamination. By comparing matching samples taken from animals at the dirty (skin) and clean (inner and outer carcass surface) areas of the slaughterline, this study aimed to assess potential Salmonella contamination routes of pig carcasses within a Portuguese abattoir. Forty-four Salmonella isolates were retrieved from 120 pigs, and further characterized through pheno and genotypical methods. Most frequent serotypes found were Salmonella 4, [5],12:i:- (47.7%), Salmonella Rissen (40.9%) and Salmonella Derby (11.4%). Isolates were most commonly collected from the skin of pigs sampled at the dirty area (59.1%), followed by the inner (38.1%) and outer (9.1%) carcass surface sampled at the clean area. Most isolates (79.5%) were considered to be multidrug resistant and all harbored the virulence associated genes invA, invH, sopB, stn, slyA, phoP, phoQ and agfA. PFGE analysis revealed that most bacterial isolates belonging to the same serotype, recovered from animals from different farms, and slaughtered at separate days were genetically undistinguishable. Furthermore, our findings suggest that Salmonella Rissen might have an increased ability to endure on the slaughterhouse environment when compared with the other serotypes. Concluding, this study shows that the slaughterhouse may be a key point for the dissemination of resistant and virulent Salmonella strains, which stresses the importance of the implementation of good hygiene practices at the slaughterhouse and of the application of corrective measures to avoid cross-contamination.