Abstract

Three hundred samples of ready mayonnaise salads and salad vegetables were used forisolation of Listeria spp. by ISO 11290-1. The isolates were identified using biochemical tests, further confirmed by duplex PCR and differentiated via conventional agglutination serotyping. A total of 8.7% of the samples harboured Listeria spp., including 7% Listeriamonocytogenes, 1% Listeria innocua and 0.7% Listeria welshimeri. The L. monocytogenes isolates were divided into four serotypes of 1/2a (61.9%), 1/2b (19%), 3b (4.8%) and 4b (14.3%). The prevalence of L. monocytogenes, especially serotype 4b indicates that ready mayonnaise salads and salad vegetables could be potent sources of listeriosis.

Key words: Listeria spp., Listeria monocytogenes, serotyping, ready mayonnaise salads, salad vegetables.