Nonaplex real-time PCR detection of Listeria monocytogenes, Campylobacter, Salmonella and enteropathogene E. coli after universal enrichment in food samples

Cell blocking: An enhancement of foodborne pathogen detection by fluorescent signals of recombinant yeasts

Cell blocking (CB) technique has been widely applied in many studies since the last century. In our research, this technique was mostly used to study the enhancement of the vacuolar response-based system that could detect Shigella sp. and Salmonella sp. investigated in previous studies. The recombinant yeast cells were blocked by mixing with agarose gel on a 96-wells plate, then storing this plate in -80 °C before using. The optimal conditions for the new system, such as agarose concentration, maximum storage time, were also established. Finally, the efficiency of the vacuolar response-based system was improved, and this system could be used as a portable detector for the foodborne pathogen.

Fast and discriminative CoSYPS detection system of viable Salmonella spp. and Listeria spp. in carcass swab samples

In this study, the complete CoSYPS Path Food workflow including all steps, namely swab sample enrichment, SYBR®Green qPCR detection of Salmonella spp. and Listeria spp., isolation and confirmation of the detected strain, was validated on beef carcass swabs. To perform the validation, the results of the complete workflow were compared, according to the ISO 16140:2003, with the ISO reference methods for detection, isolation and confirmation of Listeria monocytogenes and Salmonella spp. The results showed that the relative level of detection and the limit of detection of the complete workflow and ISO reference methods are in a range from 2 to 16 CFU/swab for both bacteria. The relative specificity, sensitivity and accuracy identified during this validation were all 100% since the results obtained with the complete CoSYPS Path Food workflow and the ISO reference methods were identical (Cohen's kappa index=1.00). In addition the complete CoSYPS Path Food workflow is able to provide detection results (negative or presumptive positive) in half the time needed as for the ISO reference methods. These results demonstrate that the performance of the complete CoSYPS Path Food workflow is not only comparable to the ISO reference methods but also provides a faster response for the verification of beef carcasses before commercial distribution.