Rapid detection of Listeria monocytogenes in foods, by a combination of PCR and DNA probe

Listeria monocytogenes is a frequent contaminant of water and foods. Its ra pid detection is needed before some foods can be prepared for marketing. In this work L. monocytogenes has been searched for in foods, by a combinatio n of polymerase chain reaction (PCR) and a DNA probe. Both PCR and the prob e were prepared for recognizing a specific region of the internalin gene, w hich is responsible for the production of one of the most important pathoge nic factors of Listeria. The combined use of PCR and the DNA probe was used for the detection of L. monocytogenes in over 180 environmental and food s amples. Several detection methods were compared in this study, namely conve ntional culture methods; direct PCR; PCR after an enrichment step; a DNA pr obe alone; a DNA probe after enrichment and another commercially available gene-probe. Finally PCR and the DNA probe were used in series on all the sa mples collected. When the DNA probe was associated with the PCR, specific a nd accurate detection of listeria in the samples could be obtained in about a working-day. The present molecular method showed some advantages in term s of rapidity and specificity in comparison to the other aforementioned tes ts. In addition, it resulted as being easy to handle, even for non-speciali zed personnel in small diagnostic microbiology laboratories. (C) 2001 Acade mic Press.