Isolation of Yersinia enterocolitica from raw milk

Four enrichment procedures were used for examining 131 raw milk samples for the presence of Yersinia enterocolitica. Forty-two isolations were obtained from 19 pooled- (31.1 percent positive) and 10 individual-producer samples (14.3 percent positive). Enrichment by Butterfields phosphate buffer incubated at 4 degrees C for 14 days and then inoculation of modified Rappaport broth incubated at 23 degrees C for 5 days produced the greatest number of isolations. The majority of isolates were biotype 1, and many were atypical from clinical isolates in being rhamnose positive (47.6 percent), citrate positive (16.7 percent), and lactose positive (26.2 percent). Thirteen isolates were serotypable, belonging to seven different O serotypes, with O:5 occurring most frequently.