Abstract
The number of enterohemorrhagic Escherichia coli O157: H7 (EHEC O157) in the female housefly feces excreted on foods such as raw beef and boiled potato was counted after contact with flies 3, 24 and 48 hr after 10^6 and 10^9 colony-forming units (CFU)/ml EHEC ingestion. In the experiment of ingestion of 10^6 CFU/ml, a small number of EHEC was detected in all harvested samples just after feeding contact. EHEC O157 of 10^2-10^8 CFU were detected from the harvested food around eosin-stained excreta, when the foods were preserved overnight at 29℃ after feeding contact. EHEC O157 of 10^2-10^5 CFU were counted from the harvested food with excreta of 10^9 CFU/ml ingested flies just after food contact. The EHEC O157 in the excreta on the foods drastically proliferated ranging 10^2-10^5-fold (10^2-10^4 and 10^3-10^8 CFU) overnight at 29℃. These results suggested that the small number of EHEC O157 excreted on the foods by EHEC O157-contaminated houseflies is a possible source of food poisoning under inadequate preservation. Complete sanitary arrangements with fly-proof structure in the cooking facilities and by food manufacturers is strongly recommended.
