Multiplex real-time PCRs for detection of <i>Salmonella</i>, <i>Listeria monocytogenes</i>, and verotoxigenic <i>Escherichia coli</i> in carcasses of slaughtered animals

Abstract

Abstract Introduction: The study objective was to develop and evaluate a new TaqMan multiplex real-time PCR method for Salmonella , L. monocytogenes , and verotoxigenic Escherichia coli (VTEC) detection in slaughtered animal carcasses. Material and Methods: The procedure included an enrichment step, DNA extraction, and two multiplex real-time PCRs. The first PCR detected the invA and hly genes of Salmonella and L. monocytogenes respectively, the second the vtx1 , vtx2 , and eae genes of VTEC. Results: The validation of this method resulted in 100% relative sensitivity, specificity, and accuracy as compared to the reference ISO methods. The limit of detection per swab sample was established at 1 cfu for Salmonella and L. monocytogenes and 2 cfu for VTEC. The authors analysed 265 slaughterhouse-collected swabs from cattle, pig, and poultry carcasses. Among 125 from cattle, 51 were positive for VTEC, 29 for Salmonella , and 1 for L. monocytogenes . Among swabs from pig carcasses (n = 95), three, two, and one sample were positive for these pathogens respectively. None of the microorganisms tested for was identified in 45 samples of poultry origin. Conclusion: The obtained results showed that the method developed can rapidly identify the main bacterial pathogens that may contaminate carcasses of food-producing animals.