Salmonella investigation uncovers cooking method risk
There was an increase in Salmonella Thompson cases throughout three border regions in Quebec in November 2016.
Eighteen cases of S. Thompson were identified through whole genome sequencing.
The Salmonella serotype belonged to serogroup C1 and since 2012, an average of 60 to 70 cases are reported annually in Quebec.
Cooking should render bacteria inactive
Chicken cooked in the shawarma style (shish taouk) was the common food eaten or probably eaten in the majority of the cases.
“With this method of cooking, the raw meat may be in contact with the cooked meat,” said researchers.
“When a restaurant is busy, it is possible that cooking times may not be adhered to and the meat served may contain parts that are undercooked.
“To prevent cross contamination or undercooking, restaurants of this type sometimes cook the meat a second time before serving it to customers. Cross contamination may also have occurred in the handling of the raw chicken.”
Onset dates of symptoms for the 16 cases that presented enteric symptoms were November 21-December 2, 2016. Two cases that had atypical symptoms were not reported until February 2017.
Chicken shawarma
Chicken shawarma is a specialty food that originates in the Middle East and is prepared by placing marinated meat (chicken, beef or lamb) on a spit to form a cone shape that is roasted in front of a grill. The meat around it is sliced off as needed and served in pita bread or with rice and condiments
The age range was less than one to 69 years and six cases were hospitalized.
Among the 18 cases, 16 had eaten or probably eaten chicken shawarma at the same restaurant chain and nine ate it at the same restaurant.
In total, five restaurants from the chain in three border regions of Quebec were identified.
In December 2016, DSPublique of Montréal notified the Bureau de surveillance et de vigie (BSV) of the Ministère de la Santé et des Services sociaux (MSSS) of a cluster of five cases of Salmonella serogroup C1 in a group of people between the age of 13-19.
The suspected source of contamination was a fast food restaurant chain serving chicken shawarma (shish taouk).
In the survey, 13 of the 16 cases that presented with enteric symptoms reported eating chicken shawarma type food at restaurants associated with the same fast food chain during their exposure period within the last two weeks of November 2016. Nine cases ate at the same restaurant.
A fourteenth case had chicken shawarma regularly at one of the chain restaurants within that period but was not able to specify the date.
Of the two cases that did not go to the restaurants, one had eaten chicken at an Asian restaurant and the other had purchased bagged raw turkey at a supermarket.
Inspection and product testing results
During inspections by Montréal’s DIA and the MAPAQ, shortcomings were observed including storage temperatures, cleaning and sanitation and risks of cross contamination.
The restaurant chain is supplied by a central kitchen that distributes raw marinated chicken to its affiliated restaurants. The central kitchen is supplied by three Quebec abattoirs.
“It is therefore possible that one batch of chicken from one or more of these three abattoirs could have been contaminated by S. Thompson and distributed over the course of this period throughout this restaurant chain.
“According to the food safety surveys, about 40 restaurants received the batches of chicken in question; however, only five restaurants were implicated.”
DIA inspection of an Asian restaurant, where food was consumed by a person who had symptoms of infection by S. Thompson belonging to the same strain in the outbreak, determined the chicken supply for the restaurant came from two of the three abattoirs.
A total of 33 food samples were taken at the restaurants and the central kitchen. No strains of S. Thompson were isolated.
The time between onset of symptoms and reporting of cases is around 10 to 14 days so chicken sampled at the central kitchen and in the restaurants did not come from the batch delivered and consumed during the exposure period.
One sample from the Asian restaurant was positive for S. enteritidis.
Source: Can Commun Dis Rep. 2017; 43:211-7
“Salmonella Thompson outbreak associated with consumption of chicken shawarma and the usefulness of genome sequencing in the investigation”
Authors: Gaulin C, Fiset M, Duchesne C, Ramsay D, Savard N, Urbanek A, Pilon PA, Usongo V, Bekal S.
