Selective culturing of Yersinia enterocolitica at a low temperature.

Stool specimens from patients with suspected Yersinia enterocolitica (Y. ent.) infection were cultured at +4 degrees C in a nutrient broth for 5 days and at the same time the same stool specimens were cultured by the routine method of the laboratory. The routine method gave 34 Y. ent. isolations. Selective culturing at +4 degrees C succeeded in isolation of the same 34 Y. ent. strains but also 15 further strains or a 44% increase in yield. Serial dilutions in broth of 34 strains of Y. ent., 7 strains of Y. pseudotuberculosis and 14 strains of other gram-negative enterobacteria were cultured at +4 degrees C. Colony counts were performed from each dilution after 2 and 5 days. Human pathogenic strains of Y. ent. (serotype 3, 8, 9) increased markedly at +4 degrees C in contrast to the other gram-negative enterobacteria.