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H.-J. E. PANG, V. Gomes, and K. R. Matthews. Dept. of Food Science, Rutgers, The State Univ. of New Jersey, 65 Dudley Rd., New Brunswick, NJ 08901-8520 Listeria monocytogenes is a widespread foodborne pathogen associated with severe foodborne illness in humans. Food composition, processing, storage, distribution, and handling conditions are factors that may individually or collectively contribute to the pathogen's ability to cause human illness. Using the guinea pig as a human surrogate, we investigated the impact of improper food handling practices on infectivity of L. monocytogenes. Improper handling of chocolate milk included leaving the milk at an elevated temperature (37oC; similar to a hot summer day in the sun) and then placing the milk in the refrigerator (4oC). The chocolate milk was artificially contaminated with L. monocytogenes prior to exposure to improper handling conditions. Guinea pigs were given per-oral 102 or 108 CFU of L. monocytogenes suspended in 1 ml of either nutrient broth or chocolate milk that had been exposed to improper handling conditions. A group of animals received per-oral 102 or 108 CFU of L. monocytogenes cultured overnight and suspended in 1 ml of water. L. monocytogenes was not recovered from the spleens or livers of animals receiving the low dose. Animals fed the high dose (108 CFU) of L. monocytogenes had similar populations of the pathogen in the spleen and liver, regardless of the food matrix. On day 2, for animals challenged with L. monocytogenes suspended in water, the initial numbers of L. monocytogenes in the mesenteric lymph nodes and liver were ~ 3 to 4 log lower or not detectable, respectively. On day 4, bacterial populations for all treatments were similar. From a food safety perspective, results are significant in that low dose (102 CFU) did not result in a listerial infection. Under the conditions tested in this study, the food carrier and exposure of the pathogen to improper handling practices had no effect on the establishment of listerial infection in the guinea pig.
Session 33, Food Microbiology: General
2005 IFT Annual Meeting, July 15-20 - New Orleans, Louisiana |