Prevalence and contamination levels of Listeria monocytogenes in retail foods in Japan

Retail foods in Japan were surveyed for the presence and contamination levels of L. monocytogenes. It was isolated from 12.2, 20.6, 37.0 and 25.0% of 41 minced beef, 34 minced pork, 46 minced chicken and 16 minced pork-beef mixture samples, respectively. MPN values were higher than 100/g in five (10.9%) minced chicken samples, but lower than 100/g in all minced beef, pork and pork-beef mixture samples. The organism was also isolated from 5.4% of the 92 smoked salmon samples at MPN values lower than 10/g, and from 3.3% of 213 ready-to-eat raw seafood samples at MPN values from lower than 0.3 to higher than 100/g. None of the 285 vegetable samples were contaminated with L. monocytogenes. These findings indicate that ready-to-eat raw seafoods are relatively high risk among the foods surveyed in this study.