Comparison of four real-time polymerase chain reaction-based methods for the detection of Salmonella enterica in food

Four real-time PCR-based methods for the detection of Salmonella (S) enterica in food, namely, TaqMan Salmonella enterica Detection Kit, iQ-Check Salmonella, BACIdent Salmonella spp., and our in-house method (Kuchta et al., 2007), were evaluated. All methods produced definitive results on the next day after sample receipt and contained an internal amplification control to monitor potential false negative results. Five naturally contaminated food samples and 20 food samples artificially contaminated with S. enterica at a level of 10 degrees cfu/25 g were analysed by the real-time PCR-based methods in parallel to the standard microbiological method EN ISO 6579. Using the TaqMan kit, positive results (identical to EN ISO 6579) were obtained with all but one food sample (naturally contaminated minced meat), which was attributed to an inappropriate enrichment used with this kit. Using the iQ-Check kit, positive results (identical to EN ISO 6579) were obtained with most food samples, but PCR inhibition was observed with some samples (artificially contaminated cream cakes). This was attributed to a lower efficiency of the lysate purification procedure of the kit with this type of food samples. Using the BACIdent kit, positive results (identical to EN ISO 6579) were obtained with most food samples, but false negative results were obtained with naturally contaminated black pepper as well as with artificially contaminated red pepper, bread crumbs and with some samples of ice cream. This was attributed to a lower sensitivity of the PCR system, which was probably caused by the degradation of active components in a fully integrated reaction mixture of this kit. Further, PCR inhibition was observed with some samples of cream cakes, which was attributed to the lack of a lysate purification procedure while applying this kit, Our in-house real-time PCR-based method produced positive results (identical to EN ISO 6579) with all food samples.