Between 27th and 29th October 2009, a total of 200 students from a college in Riyadh attended the polyclinic of the college and several hospitals in Riyadh complaining of gastrointestinal symptoms after eating from the college's restaurant. An investigation was conducted to identify the implicated food item(s) responsible for the outbreak and determine the source of infection.
Methodology
A case control study was conducted. A case was defined as any student who ate from the college's restaurant between 26/10/2009 to 29/10/2009 and developed diarrheal illness within three days of food consumption. A control was defined as any student who ate from the same restaurant at the same period and did not develop diarrheal illness during the period of the outbreak. A total of 140 cases and 140 controls were enrolled in the study. Self-administered questionnaires were distributed to study subjects to collect information about food items, symptoms, and admission history.
Results
Out of 140 cases, 95.7% presented with diarrhea. Fever was reported by 87.9%, abdominal pain by 87.1%, nausea by 51% and vomiting by 36.4%. Among food and drink items "Umm Ali" Sweet had the highest odds ratio (OR= 10.5, with 95% C.I 6.0 - 18.2). An epidemic curve was drawn and it was typical of a point source outbreak. Salmonella enteritidis group D was isolated from stool or rectal swab specimens of five students and three food handlers. The same organism was also grown from a swab taken from one food utensil.
Conclusion
On the basis of this investigation, this foodborne outbreak was caused by Salmonella enteritidis and Umm Ali sweet was the implicated food item. Raw eggs were the most likely source of infection, while time-temperature abuse during preparation and storage of Umm Ali sweet was the most important contributing factor leading to this outbreak. Education of the food handlers about the hygienic preparation of food should be emphasized.