Prevalence of Listeria monocytogenes in intestinal contents of healthy animals in Japan.
A total of 1705 faecal specimens or ileo-caecal contents of cattle, pigs, dogs, cats, fowls and rats were submitted for the isolation of Listeria monocytogenes by the use of the combination of Oxford-LPM agar plates after the cold enrichment in PBS at 4°C for 4-6 weeks. Prevalence of L. monocytogenes was found to be 1.9% in cattle, 0.6% in pigs, 0.9% in dogs and 6.5% in rats. However, no L. monocytogenes was isolated from chicken or cats. Among 26 isolates of L. monocytogenes, 13 strains (50%) were classified into types 1/2a (3 strains), 1/2b (5 strains) and 4b (5 strains) and were often associated with human listeriosis. The majority of the Listeria spp. other than L. monocytogenes isolated from these animals was found to be L. innocua.