Studies on the pathogenicity of Yersinia enterocolitica and Y. enterocolitica-like bacteria. 1. Enterotoxin production at 22 degrees C and 37 degrees C by environmental and human isolates from Scandinavia.

Altogether, 412 strains of Yersinia enterocolitica and Y. enterocolitica-like bacteria from environmental and human sources were examined for their ability to produce enterotoxin at 22 degrees C and 37 degrees C using the infant mouse assay. A total of 73 strains were positive at 22 degrees C, only. Another 28 strains were positive both at 22 degrees C and 37 degrees C. Of these 28 strains, 26 were sucrose and aesculin non-fermenting and all were Voges-Proskauer negative. All of these strains were isolated from non-human sources. All of 13 strains belonging to O-serogroup 28 produced enterotoxin at 37 degrees C. The results indicate that enterotoxin production at 22 degrees C is widespread in Y. enterocolitica with the highest prevalence among human clinical isolates. Enterotoxin production at both 22 degrees C and 37 degrees C seems to be common in Y. kristensenii (sucrose non-fermentors). Enterotoxin production is apparently rare in Y. frederiksenii (rhamnose fermentors) and in Y. intermedia (rhamnose and melibiose fermentors).