Molecular characterization of Listeria monocytogenes isolated from a ready-to-eat fermented milk and cereal product, Fura-de-Nunu

This study was conducted to determine the occurrence of Listeria (L.) monocytogenes in Fura-de-Nunu, a ready-to-eat (RTE) fermented milk (Nunu) and cereal (Fura) blend, the serogroups as well as the virulence of the isolates. A total of 75 Fura and 75 Nunu samples were examined. Listeria species were isolated on PALCAM medium and Listeria chromogenic agar, and identified phenotypically according to International Standardization Organization (ISO) procedures. Identification of L. monocytogenes, serogrouping and detection of virulence genes were carried out by polymerase chain reaction (PCR). Listeria spp. were recovered from 23 (30.67%) and 41 (54.67%) samples of Fura and Nunu, respectively. The bioloads of Listeria ranged from 103 to 105 CFU/ml. Six presumptive species of Listeria were identified from the samples, with L. monocytogenes accounting for 21.00 and 20.64% of isolates from Fura and Nunu, respectively. Out of the three major serogroups (1/2a, 1/2b and 4b) associated with human disease, only 1/2a and 4b were identified among the isolates. Some of the isolates tested positive for the presence of virulence genes, hlyA and iap. Results from this study show that Fura-de-Nunu, may represent a risk for transmission of listeriosis to consumers. Key words: Listeria monocytogenes, Fura-de-Nunu, fermented milk, ready-to-eat, Listeriosis.