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Loyalty Cards Help to Trace Salmonella Outbreak

05 February 2012

An outbreak of salmonella poisoning in France towards the end of last year was traced to dried pork sausage from one producer thanks to the use of supermarket loyalty cards, writes TheMeatSite Editor in Chief, Chris Harris.

On 7 December 2011, the National Reference Centre for Salmonella (NRC) alerted the French Public Health Institute (InVS) about a two-fold increase of Salmonella enterica serotype 4,[5],12:i:- since the first week of November.

Between 31 October and 18 December, a total of 337 cases were identified.

The average age of those affected was 10 years old with about 30 per cent being children under five.

A majority of women were affected and cases were reported throughout France.

The report by C M Gossner1, D van Cauteren, S Le Hello, F X Weill, E Terrien, S Tessier, C Janin, A Brisabois, V Dusch, V Vaillant1, N Jourdan-da Silva for the European Food Safety Authority says that an epidemic of Salmonella enterica 4,[5],12:i:- was already observed about three months before this outbreak.

These two consecutive outbreaks appeared in a context of emergence of monophasic variants of Salmonella Typhimurium all over Europe in humans, animals and food products. Surveillance data from the French Agency for Food, Environmental and Occupational Health and Safety (Anses), showed that this 4,[5],12:i:- variant had been identified in multiple animal and food samples including pork and beef . While this serotype was rarely identified before the mid-1990s, it is now among the most reported Salmonella serotype in the European Union Epidemiological investigations pointed to a dried pork sausage purchased principally at a supermarket chain and consumed after the end of October 2011.

Purchases of pork delicatessen products at the supermarkets up to four weeks before the symptom onset were investigated by the DGAL using data recorded through supermarket loyalty cards.

Among the 90 interviewed cases, 39 provided the number of their loyalty card for the supermarket chain during the interview. For 17 cases no purchases of dried pork sausage could be found. Of the 22 cases with documented purchase of dried pork sausage, 15 had bought sausage from a specific French producer and the remaining seven cases bought sausages of seven different brands and origins from other producers.

Dried pork sausages from the one specific producer represented less than three per cent of the supermarket chain's sales for this type of food item.

Eleven loyalty cards from another supermarket chain were collected. However, the supermarkets from this chain bought products individually rather than centrally for the whole chain, and the products are therefore not coded in the central database and cannot be traced through the loyalty card data.

Forty-five lots of the pork sausage (one lot equivalent to 8,000 sausages) had been produced between 1 September and 15 December 2011. At the identified processor.

Between 1 October and 15 December, 80 to 100 per cent of the sausages were distributed to the one specific supermarket chain. The remaining lots were distributed to other supermarket chains including the second chain that the research team investigated and others used by the cases.

As of 15 December, the producer's own checks on raw materials and final products as well as food inspection done during the outbreak investigation of 43 samples (25 g per sausage per lot) of dried pork sausages produced between 24 August and 21 November resulted negative for Salmonella.

The sausages had been distributed nationwide in metropolitan France, the French department of La Reunion, the French overseas territories of Saint Pierre and Miquelon and French Polynesia, and also in Maurice Island. In addition, there was secondary distribution by the supermarket chain to Poland, Portugal and Slovenia.

The researchers said that the pork sausage was identified as the main potential source of the salmonella outbreak because an unusually high proportion of the interviewed cases reported having eaten dried sausage and the proportion of cases that had bought pork delicatessen products in the same supermarket chain was much higher than the market share of this supermarket chain among the different supermarket chains in France.

Then the researchers said that according to loyalty card records from the supermarket chain, around 68 per cent of the cases' purchases of sausages were sausages from the same specific producer.

However producer's sausages represent less than three per cent of the sausages market share at the supermarket chain.

"This discrepancy makes it likely that the vehicle of infection was dried pork sausage from the one producer." the researchers said.

"Finally, the fact that more than half of the production of the producer is sold through the one supermarket chain explains the high proportion of cases that purchased dried pork sausage at that supermarket chain."

The researchers added that the use of the loyalty card from the supermarket chain was important to identify the vehicle of infection and the local producer involved in this outbreak.

"These cards are used more and more and prove helpful in the investigation of food-related outbreaks," the team said.

Following the discovery of the outbreak, the research team said that despite the absence of positive food samples, control measures including withdrawal and recall were implemented.

However, the team concluded that given the limitations to detect Salmonella in dried sausages, the ability of the standard reference method to detect of monophasic variant strains in dried sausages is questionable.

The researchers called for additional methods to be explored in order to improve monitoring protocols.

Janauary 2012

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