Salmonella food poisoning outbreak in Al-Ahsa Governorate, Saudi Arabia, July 2010 (1431 H).

By the morning of Thursday 19/7/1431 H (1/7/2010), health authorities of AlAhsa governorate had noted an increase in the number of gastroenteritis cases reported from Al-Jafur General Hospital. This continued over the following day, reaching 33 cases. All cases had gastroenteritis symptoms including diarrhea, fever, vomiting, nausea, and abdominal pain. All reported a recent history of eating at Al-Gariah restaurant in Al-Ahsa the previous evening. A team from FETP was assigned to investigate this outbreak.

The team first visited the restaurant which had already been closed by the local authorities. It appeared to be generally clean. After that, the team visited Al-Jafur general hospital, and reviewed the patients’ records and laboratory results. A list of patients’ names and telephone numbers and the active surveillance done by the hospital was obtained.

A case-control study was conducted to identify the severity, extent, source, and cause of this outbreak. A case was defined as any person who had eaten from the implicated restaurant between 7:00 PM of the 30^th of June to 11:30 PM of the 1^st of July 2010, and had developed any gastrointestinal symptoms of abdominal pain, diarrhea, fever, nausea and vomiting, within days of food consumption. A control was defined as any person who had eaten from the same restaurant during the same time period and had not developed any of these symptoms during the period of the outbreak.

At the day of the team’s arrival to Al-Ahsa, all the admitted cases had already been discharged from the hospital. Data was collected both by face to face interviews at the patients homes or by telephone. Two controls were selected for each case from his/her relatives or friends, who had eaten from the same restaurant and had not become sick. Rectal, under nail, throat and nasal swabs had been taken from all the restaurant workers and from the patients for culture. Various food specimens from the restaurant had been sent to King Fahd Hospital laboratory for investigation. Cultures of patients’ stool or rectal swab were also done.

A total of 100 people were interviewed, 33 cases and 67 controls. Among the cases, there were 10 males (30%) and 23 females (70%). Among the control, there were 44 males (65.7%) and 23 females (34.3%). Age of cases ranged between 3 – 71 years (mean ± SD of 25.7 ± 14.0 years). Among cases 32 (97%) were Saudi nationals. All had developed gastroenteritis manifested by abdominal pain in 32 (97%), diarrhea 30 (90.9%), fever 29 (78.8%), vomiting 25 (75.8%), and nausea 10 (30.3%).

The first case had onset of symptoms at 1:00 am on Thursday 1 July while the last case had onset at 4:00 pm of Friday 2 July, 2010. The incubation period ranged between 5 to 20 hours (mean ± SD of 9 ± 13 hours, median 8:45 hours, mode 7:00 hours). The epidemic curve was suggestive of a common source outbreak. (Figure 1)

On questioning the restaurant workers regarding the procedures for food storage, handling, preparation, and serving, they stated that the meat kabab served on Wednesday's dinner had been prepared earlier by mixing red meat with raw eggs, in order to maintain proper shape during barbecue, and was then kept in a refrigerator for 1 to 2 days before use. On the same day, the meat kabab was semi barbecued, and then was kept at restaurant temperature till it was ordered.

Cultures of the restaurant food items showed growth of Salmonella enteritidis group D1 in the meat kabab. The same serotype of Salmonella was isolated from stool specimens obtained from eight patients. No pathogens were isolated from the restaurant food handlers. Statistical analysis showed a strong association of food poisoning with eating meat kabab, showing the highest odds ratio (OR=22.96, 95% C.I = 4.73 -151.65). (Table 1)

˗ Reported by: Dr. Hussain Al Bakheet, Dr. Abdullah Al-Zahrani, Dr. Mohammad Al-Mazroa (Field Epidemiology Training Program).

In the present outbreak, dinner on the 30^th of June at the implicated restaurant was the meal responsible for the outbreak. The “Meat kabab” prepared from mixed red meat and eggs, was the incriminating food item. The causative organism was Salmonella enteritidis which was isolated from both the patients and the meat kabab.

Clinical and epidemiological features give important clues to etiology. Fever, abdominal cramps, and diarrhea occurring within 5.5 to 20 hours of food consumption usually result from Salmonella, Shigella, and Campylobacter jejuni.² Based on clinical and epidemiological features, the present outbreak resulted from Salmonella food poisoning, which is supported by the laboratory findings. The incriminating food item, meat kabab, also strengthens this premise since eggs are known source of Salmonella organisms.³

References:

1. Center for Diseases Controls and Prevention. Fact sheet: Foodborne illnesses. Atlanta. Available from URL: http://www.cdc.gov/ncidod/dbmd/diseaseinfo/foodborneinfections_g.htm.

2. Giannella RA, Formal SB, Dammin GJ, et al. Pathogenesis of salmonellosis: Studies of fluid secretion, mucosal invasion, and morphologic reaction in the rabbit ileum. J Clin Invest 1973; 52:441.

3. CDC: Outbreaks of Salmonella serotype Enteritidis infections associated with consumption of raw shell eggs-United States, 1994-1995. MMWR 1996; 45: 737.