A comparative study of randomly amplified polymorphic DNA analysis and conventional phage typing for epidemiological studies of Listeria monocytogenes isolates.

The analysis of RAPD profiles generated by PCR with a single 10-mer, HLWL74, was compared to bacteriophage susceptibility data for epidemiological typing of Listeria monocytogenes strains. A total of 104 L. monocytogenes strains was screened, all from serogroup 1 or serotype 4b. Of these, 53 had been isolated during 6 different listeriosis outbreaks. The remaining 51 strains were chosen randomly from our collection. A total of 38 RAPD types were observed, although each epidemic group of strains isolated during one of these outbreaks displayed a specific RAPD profile. For 98% of the strains isolated during outbreaks, the correlation between RAPD typing and phage typing was complete. Only one strain, typed as epidemic by phage typing, was clearly distinguishable from the others by RAPD analysis. Among the 51 strains not related to an outbreak, 12 were linked to epidemic groups by RAPD analysis. Two of these rearrangements were supported by phage typing. The remaining 10 strains could be excluded by phage typing from any of the epidemic groups studies. Considering all 104 isolates, the decision to relate a strain to a particular epidemic group or to exclude a strain from any epidemic group was the same for 92 isolates, using either phage typing or RAPD analysis. The RAPD analysis, which is quick, simple and suited for automation, is proposed as an attractive alternative for phage typing in epidemiological studies of listeriosis.