Automated RNA probe assay for the identification of Listeria monocytogenes

Recent epidemics of human listeriosis have shown the importance of Listeria monocytogenes as a food-borne risk. We have developed an automated identification assay for L. monocytogenes using the specificity of the 16S rDNA probe described by Wang et al. (1991). Bacterial cultures were lysed quickly by a chemical step releasing the target nucleic acids. Extracts were loaded into the VIDAS automate (bioMérieux) which performed a non-radioactive hybridisation reaction for 2 h. This assay recognised specifically 68 out of 69 L. monocytogenes isolates from clinical and food origins, including serovars 4b and 12, without cross-hybridising to other Listeria species (103 strains) or other bacterial species (15 strains). The sensitivity of the assay was 107 bacteria. This automated technology is faster than conventional biochemical identification.