Evaluation of some cold enrichment and isolation media for the recovery of Yersinia enterocolitica.

An evaluation of several cold enrichment media for Yersinia enterocolitica showed that the enrichment quotient achieved after 3 weeks at 4 degrees C was highly dependent on the initial cell concentration and the medium used. The latter should be of high nutritional value, in order to allow sufficient growth of Yersinia enterocolitica at a low temperature. Enrichment in typtone--soya broth yielded better results than in--frequently used--phosphate buffer, pH 7.6. While comparing isolation media for Yersinia enterocoliica to be used after cold enrichment, DHL agar was most satisfactory: after 20 h incubation at 29 degrees C, colonies of Yersinia enterocolitica are easily distinguishable and the organisms fully recovered. An urea medium, containing novobiocin as selective agent, also yielded good results. It must be stressed that only human strains of serotypes 0:3 and 0:9 of Yersinia enterocolitica were studied.