A hospital outbreak of Salmonella food poisoning due to inadequate deep-fat frying

In an outbreak of plasmid-free Salmonella enteritidis phage type 4 (PT4) food poisoning at a hospital for mentally handicapped people in July 1990, 101 residents and 8 staff were affected and a cohort study implicated beef rissoles cooked by deep-fat frying as the vehicle of infection (relative risk 292, 95% confidence interval 1.73-4.93, P much less than 0.001). Replication of the cooking process demonstrated that the rissoles achieved core temperatures of only 48-60 degrees C despite external temperatures of 91-95 degrees C and an oil temperature of 142-154 degrees C. No residual food was available for microbiological testing but plasmid-containing S. enteritidis PT 4 was isolated in shell eggs from the hospital kitchen.