Detection of Listeria in Foods by Using a DNA-probe Hybridization Assay Kit

Abstract

A non-isotopic DNA-probe hybridization assay has been developed for the rapid and definitive identification of Listeria spp. in food, which is now commercially available as a kit. We have evaluated the hybridization assay kit by comparing it with a conventional culture procedure regarding 56 cheese samples (including positive samples which had been tested previously and frozen) and 50 meat samples.
For the cheese samples, 22 (39%) were positive by hybridization, while 24 (43%) were positive by the culture procedure. In the case of the meat samples, 36 (72%) were positive using UVM-2 broth and 34 (68%) positive using EB broth by the hybridization assay, while 39 (78%) were positive by the culture. With the cheese samples, 13 were positive for L. monocytogenes and for the meat samples, 19 were positive for this species. Most of the L. monocytogenes positive samples were detected by the hybridization assay.
The above data show that the positive rate by the hybridization assay was slightly lower than by the culture procedure. However, this difference is not very important from a practical standpoint. The hybridization assay results can be obtained within approximately 3 hr following two day's of enrichment. The hybridization assay is therefore useful for rapid detection of Listeria in foods.