Between 15-17 January 2008 a total of 92 patient attended to hospitals and primary health care centers in Najran city complaining of gastrointestinal symptoms after eating form a newly opened restaurant. We started an investigation to identify the food item responsible for the outbreak and determine the source of infection.
Methodology
We conducted a case control study. A case was defined as any person who ate from the restaurant between 14/1/2000 to 16/1/2008 and developed diarrhea illness within two days of food consumption. A control was defined as any person who ate from the same restaurant at the same period and did not develop diarrhea illness during the period of the outbreak. We took a sample of 50 cases and 50 controls and asked them about food consumption and symptoms and admission history.
Results
Out of all the cases, 50(100%) developed gastroenteritis manifested by diarrhea , 46(92%) fever ,44(88%) abdominal pain ,42(84%) nausea,36(72%) vomiting and 16(32%) patients had chills. Mayonnaise salad had the highest attack rate (AR) and odd ratio (OR) ( AR=93.8%,OR=21.0,95% CI = 2.6-166.5 ). Followed by broasted meal (AR=84.4, OR=19.5, 95% C.I =6.9-54.4 ) . Of those who had eaten chicken shawarma 84.6% became sick (OR=6.8, 95% C.I =1.4-32.4). Salmonella enteritidis group D was isolated from 16(80%) of patients who agreed to give stool or rectal swabs specimens, while all cultures that were taken from the restaurant food handler and food items showed no growth for any pathogens. Mayonnaise was made in the restaurant from blending egg yolks, oil and garlic was prepared by staff two to three times a week.
Conclusion
This common source outbreak of salmonella resulted from restaurant prepared mayonnaise served with the mayonnaise salad, broasted meal, and shawarma between 14/1/2000 to 16/1/2008.The serotype enteritidis suggest that the organism originated in the egg and raw egg product. Heavy contamination probably resulted from temperature abuse of mayonnaise and eggs causing high infectivity.