Genome Variation among Listeria monocytogenes Isolates Derived from Epidemiologically Related Raw Milk and Other Strains.

Listeria monocytogenes strains were examined by restriction-enzyme analysis of chromosomal DNA using a total of 18 restriction enzymes. Ten of the 6-base restriction enzymes and one 8-base restriction enzyme produced distinguishable fragments among these strains. Six strains (serotype 1/2a) recovered from raw milk suspected of the same contaminant were compared with seven epidemiologically unrelated strains (serotype 1/2a) using 10 of the 6-base restriction enzymes. The restriction enzyme patterns of the six raw milk isolates were identical to each other, but differed from those of the other strains. Restriction-enzyme analysis of the chromosomal DNA of L. monocytogenes by using the 6-base restriction enzymes may be a useful method of epidemiological analysis for listeriosis outbreaks.