Increased yields of pathogenic Yersinia enterocolitica strains by cold enrichment.

Yersinia strains recovered from routine stool cultures (n = 13,534) as well as clinical symptoms in the patients were analysed in order to establish whether enteric Yersinia enterocolitica strains recovered only after cold enrichment cultures shared the same pathogenicity markers and caused the same symptoms as strains from primary cultures. 93% of the 201 Yersinia isolates were Y. enterocolitica strains and 71% of these were of serotype O3. Nearly 40% of all Y. enterocolitica strains and 21% of serotype O3 strains were isolated only after 1 week's cold enrichment of stool specimens. Practically all Y. enterocolitica O3 strains, whether from primary or cold enrichment cultures, were pathogenic not only on the basis of the serotype but also on the basis of Congo-red uptake and calcium-dependent growth at 35 degrees C (CR-MOX test). The symptoms in patients with Y. enterocolitica O3 from primary and cold enrichment cultures were similar except that abdominal pains were more frequent (p < 0.05) in the former. Arthropathia, mesenteric lymphadenitis and erythema nodosum were detected in 15% of the patients with Yersinia isolates and were more frequent in patients with isolates from cold enrichment or without diarrhea.