Abstract
In this study, we have developed a rapid method for the simultaneous detection of Listeria monocytogenes and Salmonella spp. in foods, combining culture enrichment and a multiplex real-time polymerase chain reaction (PCR). The assay used two pre-existing primer-probe sets, labelled with different reporter dyes to enable the direct distinction of the original contaminating agent. Amplification efficiency and inclusivity/exclusivity of the combined assay was successfully assessed. The overall process included the culture enrichment based on the ISO standard, consisting of 24 h incubation in appropriate media (Half Fraser Broth for Listeria and buffered peptone water (BPW) for Salmonella), followed by a single DNA extraction of mixed enrichment aliquots, and real-time PCR detection of the hly and bipA genes of L. monocytogenes and Salmonella spp., respectively. An internal amplification control, co-amplified during the PCR run, was included in the assay to verify the results. The tool was evaluated with a variety of artificially inoculated samples of fresh products and ready to eat and cooked dishes, allowing the identification of the target pathogens down to 5 CFU/25 g of food sample. Moreover, the analysis saved a considerable amount of time compared to the ISO standard, being performed in less than 2 working days. Specificity, sensitivity and accuracy were satisfactorily tested by comparison to the standard methods ISO 11290-2:1998 and ISO 6579:2002, suggesting that the tool has a great potential as a reliable alternative for food safety assurance providing rapid detection of both pathogens in food samples.
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Acknowledgements
We wish to thank Marta Hernández of the ITACyl for kindly providing the Listeria strains. The Public Health Laboratory of the Serveis Territorials de Girona, Agència de Protecció de la Salut, Generalitat de Catalunya is also acknowledged for helping with food samples.
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Ruiz-Rueda, O., Soler, M., Calvó, L. et al. Multiplex Real-time PCR for the Simultaneous Detection of Salmonella spp. and Listeria monocytogenes in Food Samples. Food Anal. Methods 4, 131–138 (2011). https://doi.org/10.1007/s12161-010-9163-3
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DOI: https://doi.org/10.1007/s12161-010-9163-3