TYPING OF LISTERIA SPP BY RANDOM AMPLIFIED POLYMORPHIC DNA (RAPD) ANALYSIS

Random amplified polymorphic DNA (RAPD) analysis, a variation of the p olymerase chain reaction (PCR) in which a single primer is used, was e valuated for use as a simple and reliable method with which to type Li steria spp. Representatives of six species of Listeria were studied. F ive isolates of L. innocua and four isolates of L. seeligeri were all distinguishable from one another, but the four isolates of L. ivanovii tested, although distinguishable from other Listeria spp., were not d ifferentiated. Among L. monocytogenes serovars 1/2a (eight isolates), 1/2b (eight isolates) and 4b (10 isolates), at least six, three and si x RA.PD patterns were observed, respectively. Fourteen neonatal cross- infection sets of L. monocytogenes isolates, shown to be indistinguish able by serotyping and phage typing, were examined with three differen t primers. With one primer, three of the sets were shown to consist of closely related, but distinguishable, strains. In the other 11 cases, each set of strains was indistinguishable with all three primers. The se preliminary data indicate that RAPD analysis has promise as a metho d for typing Listeria spp.