Consumption of meat contaminated with Yersinia pestis can cause oro‐pharyngeal plague in humans. Existing microbiological media designed for selective detection of Y. pestis in food are not satisfactory for that purpose. Expression of genetic determinants in Yersinia species including low calcium response (Lcr), colony size, crystal violet (CV) binding, Congo red (CR) uptake, autoagglutination (AA) and hydrophobicity (HP) were compared. Lcr and CV binding were detectable within 24 h at 37C in Yersinia enterocolitica and Yersinia pseudotuberculosis but at 48 h in Y. pestis. Colony size, AA, and HP characteristics were expressed in Y. pseudotuberculosis and Y. enterocolitica, but not in Y. pestis. CR uptake in Y. pestis was demonstrated only on calcium‐deficient CR‐magnesium oxalate (CR‐MOX) tryptic soy agar but was expressed on both CR‐MOX and low‐calcium agarose medium for Y. pseudotuberculosis and Y. enterocolitica. CR‐uptake phenotype by Y. pestis can be used for the detection of this pathogen in foods.
PRACTICAL APPLICATIONS
Yersinia pestis, Yersinia enterocolitica and Yersinia pseudotuberculosis can cause diverse human diseases. Y. enterocolitica and Y. pseudotuberculosis can cause intestinal distress when consumed in contaminated food. Y. pestis, the causative agent of bubonic plague in humans, is also found in food and can cause febrile illness in humans. Thus, food can have a significant role in the dissemination of human plague. There is a concern for risk assessors about the presence of Y. pestis in food. A virulence plasmid of 70 kb is directly involved with virulence of these pathogens. Until now, separating Y. enterocolitica and Y. pseudotuberculosis from Y. pestis required sophisticated molecular biology and immunological techniques. This problem was eliminated by analyses of virulence plasmid encoded phenotypes as simple and reliable targets for the rapid detection of Y. pestis. These classical microbiological assays should greatly assist both regulatory agencies and the food industry in the detection of Y. pestis. Further, these techniques should also greatly assist medical and public health laboratories to identify this pathogen.