Significance of milk as a possible source of infection for human yersiniosis I. Incidence of Yersinia organisms in raw milk in Shimane Prefecture,Japan

Twelve strains of Yersinia enterocoliticaa and 4 strains of a Y. enterocolittica-like organism (Y. intermedia) were isolated from 374 pooled raw milk samples. Growth occurred in a cold enrichment system using phosphate buffer solution (7 strains), peptone solution (5 strains) and yeast extract—casein—cystine broth (5 strains) Serovar 13,7 was most frequently isolated (8 strains) followed by serovars 5,27 (2 strains), 6,31, 7,8, 14 and 22 (each one strain). Two strains were untypable, serologically. Seasonal variation was of little consequence, but the regional incidence was an important feature of the bacteriological findings. Autoagglutination tests gave negative results with all isolates. Although so-called “clinical strains” were not identified, the relationship of the strains of Yersinia to milk-borne infections in humans cannot be excluded.