ANTI-DNA.RNA ANTIBODIES - AN EFFICIENT TOOL FOR NONISOTOPIC DETECTIONOF LISTERIA SPECIES THROUGH A LIQUID-PHASE HYBRIDIZATION ASSAY

This study was undertaken to evaluate the potential of a new approach using anti-DNA . RNA monoclonal antibodies to detect Listeria in both pure culture and inoculated meat and meat products. A sensitive liquid -phase assay was first developed, based on the formation in solution o f a hybrid between a 784-bp DNA probe, specific for the genus Listeria , and target rRNA. Monoclonal antibody and antisera raised against hyb rid nucleic acids were then used in various immunoenzymatic assays to detect specific hybrids formed in solution. System 2, using a double s andwich enzyme-linked immunosorbent assay, and system 1, using a bioti nylated probe, proved to be very effective. The method using biotin-st reptavidin complex, however, resulted in a higher background signal. S ystem 2 described here, using unlabeled probe, was more effective. Thi s strategy allowed the detection of as little as 2.5 pg target RNA fro m pure culture and 500 cells from inoculated meat homogenate, even in the presence of other contaminating bacteria. The assay was more sensi tive and could be completed within 3 h, as opposed to several days whe n conventional culture methods were used.