Human foodborne listeriosis has been mainly linked to the consumption of meat and dairy products, however, the incidence of Listeria monocytogenes has increased in fresh-cut fruit and vegetables in the last years because of their increasing consumption. L. monocytogenes contamination of food products may occur in different ways because of its ubiquitous nature. Within EU project Quafety on quality and safety of fresh-cut fruit and vegetables, the research group led by Professor Eleftherios Drosinos from Agricultural University of Athens assessed the serotype prevalence and the biodiversity of L. monocytogenes isolates from naturally contaminated minced meat, fruits, and vegetables.
121 L. monocytogenes strains were isolated from fresh minced pork, cucumber, rocket, and strawberry samples during prevalence studies.
Serotyping was performed with multiplex PCR, and the biodiversity was assessed with random amplified polymorphic DNA (RAPD) PCR analysis using M13, UBC155, and HLWL85 as primers and with repetitive element palindromic PCR analysis using (GTG)5 as the primer.
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The present study showed that the majority of the meat L. monocytogenes isolates belonged to serotype 1/2a, with occasional presence of serotypes 1/2b, 1/2c, 4b, and 4a, 4c, or 4ab. For fruits and vegetables, all L. monocytogenes isolates belonged to serotype 4b. Moreover, the combination of (GTG)5 primer with those of RAPD-PCR analysis resulted effective in discriminating the isolates highlighting the great diversity of pathogen strains in naturally contaminated food samples.
Professor Drosinos concludes: "The high level of biodiversity observed in L. monocytogenes isolates from naturally contaminated food products should be considered when designing or developing intervention strategies."
Source: Hadjilouka A., Andritsos N.D., Paramithiotis S., Mataragas M., Drosinos E.H., "Listeria monocytogenes serotype prevalence and biodiversity in diverse food products", December 2014, Journal of Food Protection, Vol. 77 (12), pages 2115-2120.
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