Family outbreak of yersiniosis.

Yersinia enterocolitica biotype 1, serotype O:21 was isolated from feces or rectal washings of three members of one family in northwestern Saskatchewan. The three isolates gave positive pathogenicity tests in guinea pigs with cultures grown at 22 degrees C as inoculum. All three cases showed clinical symptoms consistent with yersiniosis. All three cases had symptoms of diarrhea and abdominal pain, and two cases had recorded fever. In two cases, appendicitis was initially suspect. One case with ileitis and peritonitis was fatal. The environmental source of the infection was not found, but river water, milk, and person-to-person spread are discussed as possible sources of the infections. The need for microbiology laboratories to culture stool specimens specifically for Y. enterocolitica, using cold-enrichment techniques is emphasized. This family outbreak of yersiniosis provides further evidence that certain biotype 1 strains of Y. enterocolitica are pathogenic.