Prevalence, biofilm formation and virulence markers of Salmonella sp. and Yersinia enterocolitica in food of animal origin in Poland

Examination of 330 food samples (meat, white raw sausage, smoked meat and cheeses) was conducted and the Salmonella spp. and Y. enterocolitica prevalence were determined. For isolated strains of Salmonella spp., it was determined whether they were of S. Typhi, S. Typhimurium or S. Enteritidis serotypes. Isolated Y. enterocolitica strains were biotyped. Moreover, the strains' ability to form a biofilm and presence of virulence factors was determined. Salmonella spp. were found in 16 (5.5%) samples, whereas Yersinia enterocolitica in 7 (2.1%) samples. Serotyping resulted in classifying 4 strains as S. Typhimurium, 2 as S. Enteritidis and none as S. Typhi. Ten strains were not classified as any of the determined serotypes. The gene invA was found in all Salmonella strains and spvC was found in 3 (18.7%) strains. All of the Y. enterocolitica were classified as biotype 1A, none of the strains had the genes ail or ystA, and the ystB gene was found in five strains. None of the 16 strains of Salmonella spp. and the 7 strains of Y. enterocolitica showed any strong ability to form a biofilm, while 7 strains of Salmonella spp. and 3 strains of Y. enterocolitica showed a moderate ability to form a biofilm.