Detection of pathogenic and spoilage micro-organisms in food with the polymerase chain reaction

Traditional biochemical and immunochemical methods for the detection of micro-organisms in food have been supplemented by a number of DNA-based methods during the last decade. Besides the development of direct hybridization techniques, emphasis has been laid on in vitro amplification methods. in vitro methods such as the self-sustained sequence replication (3SR) or the nucleic acid sequence based amplification (NASBA), the Q-beta replicase amplification and the ligase chain reaction (LCR) have had, until now, only limited practical relevance for food monitoring and control. The most developed in vitro amplification method is the polymerase chain reaction (PCR) that allows rapid and selective identification of micro-organisms. Because PCR is increasingly raising interest as a detection method in food hygiene and control, an overview of PCR-systems for the detection of bacteria and viruses in food is provided with this paper. Although the PCR method has advantages (particular specificity, sensitivity) it also has limitations, one of which is its inability to allow differentiation between viable and non-viable micro-organisms. Furthermore, the inhibition of PCR by food-derived inhibitors can result in false negative results. Possible reasons for PCR inhibition and ways to differentiate between viable and dead micro-organisms are discussed in this review. (C) 1998 Academic Press Limited.