FOODBORNE OUTBREAK ASSOCIATED WITH FRIED RICE HARDIN COUNTY

FOODBORNE OUTBREAK ASSOCIATED WITH FRIED RICE, HARDIN COUNTY, MAY 2006 ASHOKA INDUKURI EPIDEMIOLOGIST LINCOLN TRAIL DISTRICT HEALTH DEPT

Foodborne Outbreak n n n On May 8 th , Hardin County Environmental office receives reports of acute gastroenteritis among 6 people who ate at a local restaurant. Illness started within 1 -6 hrs after eating dinner on May 7 th. More reports of illness received on May 9 th.

Foodborne Outbreak n Patients complain of the following symptoms developing within a short incubation period of < 6 hrs. Nausea Vomiting Diarrhea Abdominal Cramps Fever & Chills

Foodborne Outbreak n n n Hardin County Environmental Health Department contacts Environmental Director and Epidemiologist of Lincoln Trail District Health Department. Outbreak Investigation initiated. Environmental staff visit the restaurant to collect food samples.

Outbreak Investigation n 32 people were identified who ate at the restaurant. These individuals were interviewed by telephone using a Foodborne disease questionnaire. Local Hospital was alerted about the acute gastroenteritis outbreak.

Outbreak Investigation n Interviews revealed that all people who were sick ate dinner at the restaurant on May 7 th. No reports of illness among people who ate lunch. The food items consumed include fried rice, chicken, vegetables and salad.

Outbreak Investigation-Case definition n n Based on the initial investigation a Clinical case of illness is defined as “Acute gastrointestinal illness characterized by nausea, vomiting, abdominal cramps, and diarrhea occurring within 12 hours of food consumption at the restaurant”. 26 out of the 32 people interviewed matched the case definition.

Outbreak Investigation n n Food samples of steamed rice, chopped vegetables and uncooked chicken were collected from the restaurant on May 8 th and sent to State Lab. Stool specimens of sick patients, and a carryout box with fried rice were also submitted.

Outbreak Investigation n n Environmental inspection of restaurant was performed on May 9 th with extensive review of food preparation, handling and storage procedures. Based on the inspection the restaurant was issued a notice of suspension the same day.

Outbreak Investigation-Results n n 26 people were sick. The median incubation period was 3 hours and the symptoms resolved in 12 hours after onset. The main symptoms included nausea(88. 5%), vomiting(88. 5%), diarrhea(65%) and abdominal cramps(62%). None of the sick people were hospitalized.

Table 1: Epi Curve for B. cereus Foodborne Outbreak

Outbreak Investigation-Results n n Fried rice was only food significantly associated with illness. Of those who consumed fried rice 93% were ill. Food specific attack rate among ill was 100% for persons who ate fried rice. Other food items with some association were vegetables and salad.

Outbreak Investigation-Results n n n Environmental inspection revealed improper handling and storage of rice. Rice cooked during lunch was stored at improper temperatures and served during dinner. There were many food code violations in the kitchen and the equipment was not well maintained.

Outbreak Investigation-Results n n The restaurant scored low rating score of 57/100 and was immediately closed. The owner was advised to rectify the violations and apply for re-instatement. Re-inspection was performed on May 11 th. Restaurant was reopened after securing a rating score of 97/100.

Outbreak Investigation-Lab Results n n n Lab results of the food samples revealed 4. 1 million colony forming units (CFU) of Bacillus cereus/gram of steamed rice. The carry-out box sample and chopped vegetables had 75, 000 CFU/gram and 120 CFU/gram of B. cereus respectively. No additional foodborne pathogens were detected.

Bacillus cereus n n n Bacillus cereus is a rare infectious case of foodborne illness. Accounts for less than 1% of foodborne outbreak cases reported to CDC. Spore-forming bacterium found in soil, vegetation and many raw and processed goods.

Bacillus cereus Spores of B. cereus survive & multiply in contaminated food and cause two types of illness by production of exotoxins or enterotoxins. They are 1. Emetic syndrome n 2. Diarrheal syndrome

Bacillus cereus n n n Emetic syndrome is associated with consumption of toxin in boiled or fried rice. Short incubation period of 1 -5 hours and 6 -24 hour duration of illness. It mostly has Upper gastrointestinal symptoms such as nausea, vomiting and can also cause diarrhea and abdominal cramps.

Bacillus cereus n n n Diarrheal syndrome is associated with consumption of contaminated meat products, soups, sauces, and vegetables. Onset of symptoms occurs within 8 -16 hours and subsides within 12 -24 hours. Symptoms include watery diarrhea, abdominal cramps and occasional nausea & vomiting.

Bacillus cereus n Diagnosis of B. cereus food poisoning can be confirmed by isolation of more than 105 B. cereus organisms/gram of contaminated food.

Discussion n Positive lab test of 4. 1 million CFU of B. cereus/gram of fried rice confirmed B. cereus as the causative organism of this outbreak. Improper storage of cooked rice at room temperature, preparing food several hours before serving might have predisposed the production of heat-stable toxin of B. cereus. This resulted in the Emetic syndrome type of B. cereus food poisoning.

Closing Notes n Consider B. cereus in your investigation / differential diagnosis in a foodborne outbreak with a very short incubation period and consumption of fried rice.

References Foodborne Outbreak Associated with Fried rice in Hardin County, KY, May 2006 -Volume 41, Number 11, Kentucky Epidemiology Notes & Reports.