AN IMPROVED ENRICHMENT PROCEDURE FOR THE ISOLATION OF YERSINIA-ENTEROCOLITICA AND RELATED SPECIES FROM MILK

A new enrichment procedure is proposed to improve the isolation of Yer sinia enterocolitica and related species from milk. This procedure use s tryptic soy broth plus Polymyxin (5 IU/ml) and Novobiocin (10 mug/ml ) - TSPN broth - incubated at 18-degrees-C for 3 d. Using raw milk and pasteurized milk inoculated with Yersinia strains, the efficiency of this procedure was compared to that of SB broth (sorbitol bile salts b roth) incubated at 4-degrees-C for up to 21 d. Despite of the presence of antibiotics in TSPN broth, there were difficulties in recovering Y ersinia organisms. Nevertheless, TSPN broth incubated at 18-degrees-C for 3 d showed better efficiency than that other method. In pasteurize d milk samples, TSPN medium at 18-degrees-C for 3 d gave better result s than the SB broth at 4-degrees-C for 7 d, showing that the proposed procedure is the preferable one due to the shorter period of incubatio n.