Testing for the recovery of Yersinia enterocolitica in foods and their ability to invade HeLa cells.

Tests have demonstrated that current enrichment methods may fail to detect low levels of some clinical strains of Yersinia enterocolitica inoculated into meats and oysters and need improvement. The results of cold enrichment with phosphate and tripolyphosphate buffers were very poor and the sensitive clinical strain failed to grow in Wauters' MgCl2 broth. Twenty typical clinical strains of Y. enterocolitica belonging to Nilehn's biotypes 2, 3, and 4 had the ability to invade HeLa cells tissue culture but none of the 52 atypical clinical and food strains belonging to Nilehn's biotype 1 or rhamnose-positive were invasive. Although temperature sensitive, this test is reproducible and useful for screening noninvasive isolates.