Submitted to: Journal of Food Safety
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 13, 2007
Publication Date: August 1, 2008
Citation: Bhaduri, S., O Connor, C. 2008. Comparison of Virulence Plasmid (pYV/pCD)-Associated Phenotypes in Yersinia Species. Journal of Food Safety. 28:453-466. Interpretive Summary: Yersinia pestis, Y. enterocolitica, and Y. pseudotuberculosis can cause diverse human diseases. Y. enterocolitica and Y. pseudotuberculosis can cause intestinal distress when consumed in contaminated food. Yersinia 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 assays should greatly assist both regulatory agencies and the food industry in detection of Y. pestis. Further, these techniques should also greatly assist medical and public health laboratories that routinely isolate and identify this pathogen.
Technical Abstract: Phenotypic expression of several virulence plasmid (pYV/pCD; 70-kb)-associated genetic determinants including low calcium response (Lcr; pin point colony, size= 0.36 mm), colony morphology (size= 1.13 mm), crystal violet (CV) binding (dark-violet colony), Congo Red (CR) uptake (red pin point colony; size= 0.36 mm), autoagglutination (AA; cells agglutinate), and hydrophobicity (HP; forms clumps) were compared among Yesinia pestis, Y. pseudotuberculosis and Y. enterocolitica. All three species demonstrated Lcr, CV binding, and CR-uptake. However, CR-uptake in Y. pestis was demonstrated only on calcium-deficient CR magnesium oxalate tryptic soy agar (CRMOX), whereas this phenotype was expressed on both CRMOX and low-calcium agarose media for Y. pseudotuberculosis and Y. enterocolitica. These phenotypes were detectable within 24 h at 37 degrees C in Y. enterocolitica and Y. pseudotuberculosis, but at 48 h in Y. pestis due to its slower growth rate at 37 degrees C. The colony morphology/size, AA, and HP characteristics were expressed in Y. pseudotuberculosis as in Y. enterocolitica, but these three phenotypes were not expressed in Y. pestis. Moreover, CR-uptake by Y. pestis in the calcium deficient medium and differences in time to express Lcr, CR-uptake, and CV binding provides the means to identify Y. pestis colonies in clinical samples, animals, and food.