EVALUATION OF THE SEROBACT(TM) AND MICROBACT(TM) SYSTEMS FOR THE DETECTION AND IDENTIFICATION OF LISTERIA SPP

The Serobact(TM) Listeria latex agglutination reagent and Microbact(TM ) 12L system were evaluated, respectively, for the detection and ident ification of Listeria in foods. The Serobact(TM) reagent proved effect ive, compared with conventional cultural methods, in the detection of low levels (1-10 cells/25 g) of both L. monocytogenes and L. innocua a rtificially inoculated into a range of foods, following enrichment. Ex tended incubation of either the primary or secondary enrichment increa sed the number of samples positive for Listeria by both Serobact(TM) a nd conventional culture, but also increased the number of false positi ve reactions. The Serobact(TM) reagent also proved effective in screen ing enrichment cultures of potentially contaminated retail food sample s. Using the USDA enrichment procedure, the Serobact(TM) reagent yield ed 100% sensitivity and 93.9% specificity, when compared to convention al culture. Identification of 81 Listeria isolates using the Microbact (TM) 12L System was compared with conventional biochemical and physiol ogical tests. While identification after 4 h was poor; due to negative or incomplete fermentation of carbohydrates and lack of haemolysis, i dentification of all but two of 81 isolates was achieved after 24h. (C ) 1997 Elsevier Science Ltd.