Serological and biochemical characteristics of 416 Yersinia strains from well water and drinking water plants in the Federal Republic of Germany: lack of evidence that these strains are of public health importance.

A total of 416 Yersinia strains from well water and drinking water plants in the Federal Republic of Germany was analysed at the National Reference Centre for Salmonella, Hamburg, in the period 1982 to 1987. Of these, 341 (82%) strains were Y. enterocolitica, 46 (11%) strains were Y. intermedia, 24 (5.8%) strains were Y. frederiksenii, and 5 strains (1.2%) Y. kristensenii. The serogroups O:3, O:9, and O:5,27 which in Central Europe are associated with human disease, were not isolated. Seventy-two strains from treated drinking water were characterized by a newly identified combination of O-antigenic factors, i.e. O:6,30,47, and 130 strains possessed a hitherto unknown O-antigen, O:59. These strains were furthermore associated with a new fimbrial antigen [K3] and a new flagellar antigen [x]. Thus, the majority of Y. enterocolitica strains cultured from drinking water plants was characterized by a rather uniform antigenic pattern which was markedly different from strains isolated from patients. Virulence tests (calcium dependency and autoagglutination at 37 degrees C) were negative in all instances. It is concluded from the results of this study that Yersinia isolates from drinking water plants are of environmental origin without pathogenic importance.