Recovery of Yersinia enterocolitica from Surfaces of Inoculated Hearts and Livers

Approximately 100 cells of Yersinia enterocolitica were inoculated onto surfaces of beef hearts and livers among 1.6 - 6.6 × 10⁴ indigenous bacteria. Two strains known to be sensitive to selenite were tested for recovery in a selenite broth: T AMU 54, which was isolated in an enteritis outbreak, was recovered in 16 of 20 trials, while a clinical strain, IP 107, was recovered in 9 of 20 trials. Variables tested in the enrichment procedure included selenite levels, beef extract levels and incubation periods. Selective agents encouraging recovery of the organism included both MacConkey agar with Tween 80 and refrigerated Bismuth Sulfite agar plates, with and without a potassium hydroxide pretreatment of the enrichment broth before streaking onto selective agars. Use of refrigerated Bismuth Sulfite agar and a 3-day incubation period of the enrichment broth provided the most consistent recovery of Y. enterocolitica .