DIFFERENTIATION OF EPIDEMIC-ASSOCIATED STRAINS OF LISTERIA-MONOCYTOGENES BY RESTRICTION-FRAGMENT-LENGTH-POLYMORPHISM IN A GENE REGION ESSENTIAL FOR GROWTH AT LOW-TEMPERATURES (4-DEGREES-C)

The growth of Listeria monocytogenes in food stored in the cold has of ten been implicated in outbreaks of listeriosis. Many subtyping scheme s have suggested that epidemic-associated strains belong to a unique g enetic group. It has not yet been possible, however, to identify molec ular or bacteriologic markers unique to epidemic-associated strains. R ecently we cloned three genes of L. monocytogenes, ltrA, ltrB, and ltr C, which are essential for growth at low temperatures (4 degrees C). T he use of a 1.2-kb PstI fragment derived from ltrB as a probe in South ern blots of HindIII-digested DNA revealed three hybridization pattern s: the first (a 5.0-kb band) was observed in strains of serotypes 4b, 1/2b, and 3b; the second (a 3.1-kb band) was seen in strains of seroty pes 1/2a, 3a, 1/2c, and 3c; and the third (a 9.5-M, band) was characte ristic of epidemic-associated serotype 4b strains. These and other dat a suggest that probes derived from this gene region that is essential for growth at low temperatures can be useful molecular tools for the s ubtyping of strains implicated in food-borne listeriosis.