Rapid Quantitative Detection of Listeria monocytogenes in Chicken Using Direct and Combined Enrichment/qPCR Method

Listeria monocytogenes is a species of foodborne pathogen often related with foods, such as poultry, ready-to-eat products, fruits, and vegetables. The culture method is a standard procedure for the detection of bacteria in food products. The real-time quantitative PCR (qPCR) technique can be used for the quantification of foodborne pathogens. The current research was aimed to assess and compare the culture, conventional PCR, and qPCR methods for detecting L. monocytogenes in chicken carcass specimens collected from various slaughterhouses situated in Mashhad in Iran. The TaqMan approach was applied for amplifying a 160 bp fragment corresponding to the prfA gene in the qPCR method. The Limit of Detection (LOD) was obtained at 27 CFU/25 g. Among 100 individual specimens tested, 13 specimens were recognized positive for L. monocytogenes using the culture method, 15 samples by the direct qPCR method, and 17 samples by the enrichment/qPCR method. From the similarity of the results of PCR and qPCR, without the enrichment stage, it can be concluded that the DNA of the bacteria killed in the specimens was due to the presence of previous contamination, which can be determined by determining the number of copies of DNA by qPCR. The severity of contamination indicates the health status of the foodstuff. Our results indicate that qPCR is an effective, quicker, and more sensitive technique for the identification of L. monocytogenes in chicken.