NONHEMOLYTIC STRAINS OF LISTERIA-MONOCYTOGENES DETECTED IN MILK-PRODUCTS USING VIDAS IMMUNOASSAY KIT

In December 1995 detection of Listeria monocytogenes Sv 1/2a in milk p roducts that were routinely sampled for investigation at the Austrian Federal Food Inspection Laboratory (Vienna) led the food manufacturer in question to withdraw his product from the market. While one of seve n Listeria strains isolated from this food product using ''VIDAS L. mo nocytogenes kit'' was undoubtedly L. monocyotogenes, six strains were nonhemolytic. In classical bacteriology haemolysin is used as an impor tant phenotypic property to differentiate L. monocytogenes from the ap athogenic L. innoctra species. Species identification by PCR and by We stern blotting confirmed that all nonhemolytic strains were indeed L. monocytogenes. Our confirmation of nonhemolytic isolates as true L. mo nocytogenes strains underlines the considerable potential of the VIDAS system as a specific immunological easy-to-use and automated test kit for detection of L. monocytogenes in food products. Whether or not th e presence of non-hemolytic Listeria monocytogenes in food products ju s tifies legal actions should be addressed by the proper authorities.