Detection and serotyping of Listeria monocytogenes in some food products from North-East of Romania

Listeria monocytogenes represents an important hazard to human health because it is capable of causing listeriosis, an atypical foodborne disease with a high fatality rate.The aim of this study was to detect and serotype Listeria monocytogenes in some food products (of animal and vegetable origin), collected during the 2011 period. The detection of Listeria monocytogenes was performed by ISO 11290- 1-A1/2004 standard method and verified by real-time PCR. Numerous subtyping strategies have been developed to characterize Listeria monocytogenes isolates. Serotyping, the traditional method for the subtype characterization of Listeria monocytogenes is not very discriminatory, but it is a universal method which gives important information on prevalence of specific serotypes. The confirmation of Listeria monocytogenes isolated strains was performed by a TaqMan real-time PCR assay, using TaqMan Pathogen Detection Kits (Applied Biosystems). The assay use specific primers and a probe for Listeria monocytogenes. In this study on a total number of 260 samples, 25 (9.61%) gave positive results for Listeria monocytogenes by conventional method and only 22 (8.46%) of them were confirmed by real-time PCR. These results indicate a high efficiency of the real-time PCR method in a short time, compared with classical methods which can provide false positive results. Four different Listeria monocytogenes serotypes were found in nine varieties of food products: 1/2a, 1/2b, 1/2c and 4b