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Differences in survival of Escherichia coli O157:H7 under various conditions that re-enact the cooking of lunches implicated in an outbreak of haemorrhagic diarrhoea

Published online by Cambridge University Press:  08 July 2005

Y. HARA-KUDO
Affiliation:
Division of Microbiology, National Institute of Health Sciences, Tokyo 158-8501, Japan
H. WATANABE
Affiliation:
Department of Bacteriology, National Institute of Infectious Diseases, Tokyo 162-8640, Japan
H. KONUMA
Affiliation:
Division of Microbiology, National Institute of Health Sciences, Tokyo 158-8501, Japan Department of Fisheries, Tokai University, Shizuoka 424-8610, Japan
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Abstract

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Two elementary schools were served lunches that were cooked in the same kitchen. An outbreak of Escherichia coli O157:H7 occurred at one school where the dishes that were prepared for the school were lukewarm and kept for 33 min at an average temperature of 45 °C before serving. However, no outbreak occurred at the other school where dishes were hot and were kept for 60 min at an average temperature of 50 °C before serving. In a series of experiments on the survival of E. coli O157:H7 in the liquid portion of similarly prepared food, the population of E. coli O157:H7 was reduced by 10−3 by heating at 50 °C for 60 min and by only 10−1 by heating at 45 °C for 40 min. Further, E. coli O157:H7 survived at 45 °C for 40 min but not at 50 °C for 60 min at pH 4·0 with a 4·0% salt concentration that was similar to that of the liquid part of the food. These results indicate that pH and salt concentration of cooked food markedly affect the survival of E. coli O157:H7 and help to explain the occurrence of the disease outbreak at only one of the schools.

Type
Research Article
Copyright
2005 Cambridge University Press