Infection caused by Yersinia enterocolitica serotype O:21.

Yersinia enterocolitica serotype O:21, biotype 3 (Wauters) was isolated from the appendix and stool of a 7-year-old girl. The same organism was later isolated in pure culture from pus from a postoperative wound infection in this patient. She developed a significant serological response (titer of 800). There was thus strong clinical evidence of pathogenicity associated with this rather uncommon human serotype. Laboratory studies in vitro and in vivo pathogenicity showed that the organism was autoagglutinable, Serény test positive, and HeLa cell invasive; when given orally to mice, it produced diarrhea and subsequently death. The results of laboratory studies of virulence correlated closely with the clinical evidence of pathogenicity in this case.