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Home catering: Salmonella

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The NSW Food Authority received a complaint on Monday, 2 February 2009 alleging several foodborne illness cases following a BBQ cultural function at a bowling club in the Eastern suburbs of Sydney.

The function had been held the previous Friday night, on 30 January.

The BBQ had been part of a weekly community gathering of over 100 paying guests held every Friday evening. It was run by a family who provided entertainment (a band) and food (a selection of salads and barbequed meats).

This business, which was most like a home catering operation, was not notified to the Food Authority which made investigating the incident more difficult.

No permission had been obtained from the Food Authority or the local council to conduct catering activities.

A joint outbreak team with officers from the Food Authority and staff of NSW Health was formed to investigate the outbreak.

In all, 13 cases linked to the function were admitted to hospital with Salmonella poisoning.

Environmental investigation

Most attendees ate their meal at the venue on the evening of the 30 January. Some, however, purchased takeaway meals or took leftover food home for later consumption.

Salads were prepared before the event in the club kitchen. Mayonnaise used was sometimes commercially-produced and sometimes made at home. Meats were cooked on the BBQ at the bowling club.

Analyses of people who were sick showed a strong association between eating a Russian Salad made with raw egg mayonnaise and symptoms of salmonellosis.

A Food Authority officer went to the bowling club on Tuesday 3 February and swabbed various surfaces in the kitchen and BBQ area for microbiological analysis. Some structural and cleanliness issues were detected. There was no dedicated hand wash basin in the kitchen and hot water from the sink, used for washing and sanitising utensils and tableware, was no more than 47°C.

Permission was given by the home caterer—who at the time was in hospital with other family members after consuming function leftovers—for Food Authority officers to sample leftover foods stored in the family home. A total of 12 food samples and 1 tea towel used at the function were taken for microbiological analysis.

Test results for samples from the home caterer’s residence indicated that the raw egg mayonnaise, raw vegetables, cooked food and the tea towel were positive for Salmonella. The swabs taken from the bowling club were negative for Salmonella.

Specialist DNA fingerprinting of Salmonella isolated from stool samples of 30 patients who attended the function showed they all had the same bacterium. This same Salmonella DNA pattern was isolated from the positive food samples, indicating that what was found in the left over food was also responsible for making those attendees ill.

Further investigation found significant gaps in the food handling skills and knowledge required by regulation of the home caterer. For example, the caterer alternated between using commercial mayonnaise and making their own from raw eggs for events but did not understand the higher risk presented by using raw eggs and the added precautions necessary when making such a product particularly in the peak of summer in a poorly ventilated domestic kitchen. The home caterer failed to notify the NSW Food Authority of their business activities despite starting regular barbeque functions 12 months earlier.

The caterer was successfully prosecuted for a number of regulatory breaches, including the sale of unsafe food, and fined a total of $20,600.

Implication: adequate skills and knowledge

This outbreak reinforces the potential dangers associated with home catering for mass events and the need for adequate understanding of the associated operational and product food safety risks.

Equally important is the corresponding implementation of risk-based management controls by the business to prevent a large scale foodborne illness outbreak.

What should businesses do?

As well as other food safety practices:

  • use safer alternatives to a raw egg based mayonnaise
  • ensure the business has adequate food safety skills and knowledge regarding their catering processes and resulting products
  • ensure that any food handling done in the home meets the operational, equipment and construction food safety requirements of the Food Standards Code
  • assess the home kitchen and the contract kitchen surfaces, equipment and services for their suitability to safely produce food
  • notify food business details to the NSW Food Authority as per regulatory requirements, which would identify the home catering business.
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