GENUS-SPECIFIC AND SPECIES-SPECIFIC DETECTION OF LISTERIA-MONOCYTOGENES USING POLYMERASE CHAIN-REACTION ASSAYS TARGETING THE 16S 23S INTERGENIC SPACER REGION OF THE RIBOSOMAL-RNA OPERON/

In this study, the 16S/23S rRNA intergenic spacer (IGS) regions of six Listeria species were examined. DNA bands of 590 and 340 bp were obse rved following polymerase chain reaction (PCR) amplification of DNA fr om Listeria monocytogenes, Listeria innocua, Listeria seeligeri, Liste ria welshimeri, and Listeria ivanovii strains with generic rRNA IGS ol igonucleotide primers. For strains of Listeria grayi subspp. grayi and murrayi, DNA band sizes of 550 and 340 bp were observed with this pri mer pair. DNA bands of these sizes were not observed for other Gram-ne gative or -positive bacteria in this PCR assay. Four RsaI digestion pr ofiles were noted for the Listeria PCR products. Listeria monocytogene s strains had one profile; L. innocua strains had a second; L. seelige ri, L. welshimeri, and L ivanovii strains had a third; and L. grayi st rains had a fourth. The small and large 16S/23S rRNA IGSs of L. monocy togenes ATCC 15313 were identical in the first 58 5' and the last 169 3' nucleotides. However, the large rRNA IGS contained a central 267-bp region with tRNA(Ile) and tRNA(Ala) genes. Large rRNA 16S/23S IGS nuc leotide sequence data has not been previously reported. This data was used to develop novel Listeria genus-specific and L. monocytogenes spe cies-specific PCR assays.