Determination of RT-PCR detection limit of live and dead Salmonella cells in raw and sterilized milk

The objective of the current study was to evaluate the reproducibility of a reverse transcriptase PCR (RT-PCR)-based technique to differentiate viable and dead Salmonella cells in raw and sterilized milk. The microorganism was initially inoculated into the milk samples followed by incubating at 37°C for 4 h prior to inactivation by heat at 80°C for 10 min. The treated and non-treated samples were subsequently monitored using both PCR and RT-PCR, in vitro. Following 4 h incubation, the invA gene of Salmonella was clearly amplified by RT-PCR, while no band was detected in the heated samples. On the other hand, using the conventional PCR, it was possible to amplify the gene in both samples. Our results may suggest an important application of the RT-PCR technique, especially when the number of live organisms is an imperative factor to produce food borne infections and to establish a detection limit of the test.