Foods usually served hot were held at various hot-holding temperatures [40°C (104°F) - 60°C (140°F] and were contaminated with fecal Escherichia coli. The contaminated hot foods were held for 1 h at each of the hot-holding temperatures during which the survival of the pathogen in each food type was evaluated. Results showed that E. coli survived hot-holding temperatures in each food type for the whole period of evaluation. A population increase occurred with time at temperatures below 50°C (122°F), while at and above this temperature there was a decrease in population with increasing time in each food type. A two-way analysis of variance using relative rates of increase or decrease (± b) showed food type to be unimportant for survival of the bacteria. A three-way analysis of variance of the same results using mean log CFU/g food showed holding temperature, food type, holding time, and the interactions of temperature and food type; and temperature and time to be significantly important for survival of the bacteria. The public health significance of these findings are discussed.

Four food types held hot at 45 to 60°C were deliberately contaminated with 01 and non-Ol Vibrio cholerae strains. These organisms were assayed for survival and recovery from the foods within 1 h of the time the food was kept hot. The results showed no growth of V. cholerae non-Ol on thiosulfate-citrate bile-sucrose agar plates after 24 h of incubation at 37°C for food held hot at 50 to 60°C. Growth was low for V. cholerae 01 and was not achieved in some instances in which foods were held at either 55 or 60°C after 40 or 60 min of from the time the food was kept hot. Both organisms, however, were recovered equally from all food types held at all temperatures after 48 h of incubation. When incubated for an additional 24 h, the organisms grew to unusually small-sized colonies, measuring 0.1 to 0.3 mm in diameter, on the same agar plates that were negative for growth after an initial 24 h of incubation. It was concluded that V. cholerae survived the period of time held at hot temperatures. Although the organisms were not recovered from some foods when held at some of the temperatures and times after 24 h of incubation, they remained viable. An incubation period of 48 h at 37°C was found to be appropriate for the recovery of V. cholerae from hot foods.