An Outbreak of Food Poisoning Associated with Restaurant-made Mayonnaise in Abha, Saudi Arabia

In May 1996, an outbreak of gastroenteritis occurred among customers who bought dinner from a restaurant that specialised in fried chicken in Abha city, south-west Saudi Arabia. The median incubation period was 10 hours (range: 3 to 27 hours). Of the 10 food items served, only mayonnaise (RR 2.52; 95% CI 1.71-3.73) and minced garlic (RR 1.20; 95% CI 1.02-1.41) were associated with cases. Salmonella enterica was isolated from 124 (84%) of the 159 persons with symptoms of food poisoning, and 91 (73%) were serogroup Enteritidis, phage type B 14. Mayonnaise was prepared in the restaurant using a regular blender. Minced garlic was prepared with the same blender immediately after making the mayonnaise. Unsafe storage of the mayonnaise at room temperature for a median of 6 hours could have resulted in overgrowth of bacteria and a high infective dose of bacteria per serving.