ABSTRACTThis report presents information on the effects of five current enrichment procedures including trypticase soy broth, phosphate buffered saline, peptone enriched phosphate buffered saline, phosphate buffered saline with sorbitol and bile salts and MacConkey broth on the stability of virulence plasmid in Yersinia enterocolitica. Virulence assays using crytal violet binding, low calcium response, Congo red uptake, hydrophobicity by latex particle agglutination, and autoagglutination as well as plasmid DNA analysis showed that Y. enterocolitica did not lose the virulence plasmid during isolation at 28C and the cells remained virulent. Moreover, postenrichment treatment with alkali to reduce competing microflora, when used in conjunction with these five enrichment techniques, did not cause the loss of the virulence plasmid, thus providing a way to selectively isolate this pathogen.
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