engleski

Detection of Food-borne Pathogens: Listeria monocytogenes by using polymerase chain reaction

According to Regulation (EC) No 2073/2005., microbiological hazards in foodstuffs form a major source of food-borne diseases in humans. Food business operators are required to comply with microbiological criteria. The Scientific Committee on Veterinary Measures identified the food categories where Listeria monocytogenes represents a hazard to public health: ready to eat foods intended for infants and ready to eat foods for special medical purposes, also ready to eat foods able to support the growth of L. monocytogenes and some products unable to support the growth L. monocytogenes. The Scientific Committee on Food issued an opinion on L.monocytogenes which recommended that the concentration of these bacteria should be below 100 cfu/g. Conventional techniques of cultivation and isolation involve pre-enrichment and enrichment broths for recovery of stressed bacteria, colony isolation on selective hard food bases, application of biochemical tests, and serotyping. These procedures are time-consuming because it takes several days to establish the identity of a particular bacteria. Therefore, new approaches are needed for the fast and efficient detection of low numbers of bacteria. Test results are dependent on the analytical method used, and therefore it is important to use an accurate and quick method to detect food contamination with this pathogen. A polymerase chain reaction is a simple and powerful method for amplification of target DNA in vitro from a small amount of template DNA. This method involves lysis of bacterial cells, extraction of nucleic acids, and the polymerase chain reaction (PCR). By cycling the reaction at different temperatures, target DNA can be exponentially amplified in approximately 80 minutes. Our laboratory performs The Sure Tect Listeria monocytogenes PCR Assay that incorporates primer and probe components for detection of the prfA gene that is highly specific for Listeria monocytogenes. The assay includes DNA template for internal amplification control for conformation of successful PCR. This assay is applicable to food control laboratories because it provides trustworthy results. The detection limit is ~1 bacterial cell in the test sample. Specificity was confirmed by testing 30 bacterial strains (ATCC strains, strains from processed foods, cheese, raw meat, smoked salmon ). No amplification was observed in non-Listeria spp. The polymerase chain reaction has been shown to be appropriate to detect L. monocytogenes as well as Listeria spp.

Listeria monocytogenes , food , prfA gene , polymerase chain reaction , Listeria spp.

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