Enterotoxin production at 4 degrees, 22 degrees, and 37 degrees C and Y. enterocolitica-like bacteria.

Production of heat-stable enterotoxin after cultivation at 4 degrees C for four days was indicated for 27 of 171 Yersinia enterocolitica and Y. enterocolitica-like bacteria, using the infant mouse assay. Of these 27 strains, 11 showed enterotoxin production at both 4 degrees and 22 degrees C, and the remaining 16 strains at 4 degrees, 22 degrees, and 37 degrees C. No strain was enterotoxigenic at 4 degrees C only. The relative prevalence of enterotoxin production at 4 degrees, 22 degrees, and 37 degrees C among Y. enterocolitica and Y. enterocolitica-like bacteria is presented. The results indicate that Y. kristensenii has a unique standing with respect to enterotoxigenicity at 4 degrees and at 37 degrees C. Y. kristensenii showed the highest prevalence of enterotoxin production at 4 degrees C (47%) and at 37 degrees C(49%). These properties were also recorded among environmental isolates of Y. enterocolitica sensu stricto, but the prevalences were low (4 and 1 %, respectively). The strains producing enterotoxin at 4 degrees C were different from those associated with yersiniosis and belonged to serogroups frequently isolated from small mammals, water, and soil (0:1, 6, 11, 12, 16, 28, and non-agglutinable). It is possible that such strains may contaminate foods and provoke food-borne intoxication involving pre-formed enterotoxins.