RAPID DETECTION OF LISTERIA MONOCYTOGENES BASED ON PCR

A polymerase chain reaction (PCR) assay targeting the gene encoding hly was developed for detecting Listeria monocytogenes in pure cell cultures and on artificially contaminated water, milk and pork. This PCR product was detected in 41 L. monocytogenes strains. In contrast, the PCR product was not detected in other Listeria spp, including innocua, ivanovii, seeligeri, welshimeri and grayi and also not in non-Listeria bacteria, indicating that the primer set was highly specific for L. monocytogenes. The detection limit of the PCR assay was 105cfu·mL-1 of pure cell culture. However, the assay could detect as few as 400 cfu · kg-1 of L. monocytogenes in pork and water and milk with 16 h of enrichment in modified Listeria enrichment broth at 30℃. The total assay time including enrichment was approximately 24 h. These results suggest that the PCR assay can be used to rapidly detect L. monocytogenes on water, milk and pork and possibly other types of food products, and the PCR assay also shows high specificity, sensitivity and being easy to handle.