Identification of viable Listeria species based on reverse transcription-multiplex PCR (RT-MPCR) and restriction digestion.

A novel method for the identification of viable Listeria species was developed based on reverse transcription-multiplex PCR (RT-MPCR) and restriction digestion. The targets for RT-MPCR were iap mRNAs whose genes are common to all Liseria species. A set of five primers was used in this study. Two of them were genus specific, and the other three were specific to L. monocytogenase, L. innocua, and L. grayi respectively. By RT-MPCR, L. monocytogenese, L. innocua, L. grayi, and a group of Listeria species, including L. ivanovii, L. welshimeri, and L. seeligeri, were specifically identified. To differentiate the latter three Listeria species, RT-MPCR products were subjected to digestion with HpaI and ScaI. The sensitivity of RT-MPCR in detecting Listeria species was determined to be 50 CFU/mL. RT-MPCR was found to discriminate between viable and nonviable cells and to detect viable Listeria species in a food model.