Yersinia enterocolitica and Yersinia enterocolitica-like bacteria in drinking water and sewage sludge.

Using an anaerobic enrichment technique Yersinia bacteria, (Y. enterocolitica and Y. enterocolitica-like bacteria) were isolated from 54% of 41 samples of drinking water and 51% of 35 samples of sewage sludge. A total of 116 strains of Y. enterocolitica sensu stricto, Y. intermedia, Y. kristensenii and other Yersinia bacteria were isolated. Y. frederiksenii was not detected in this study. The isolates belonged to 17 different serogroups, but 42% of the cultures were non-typable. The serogroups 0:3, 0:8 and 0:9, which are responsible for almost all registered cases of yersiniosis in man, were not detected. Yersinia bacteria were found in many samples of drinking water in which fecal coliforms could not be detected. Fecal coliforms were, however, found in all 5 samples from which Y. enterocolitica sensu stricto was isolated. Salmonella bacteria were found to be inadequate as indicators of the presence of Yersinia bacteria in sewage sludge. Salmonella bacteria were found only in raw sludge and sludge stored for up to one month, whereas Yersinia bacteria were found in sludge stored for up to 1 1/2 years. A comparison was made of three different selective agar media for isolation of Yersinia bacteria from the enrichment broth. The frequence of isolation with Desoxycholate Citrate Agar was significantly higher than with either Yersinia Mannitol Agar or Yersinia Peptone Agar.