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Food Safety Focus (65th Issue, December 2011) – Food Incident Highlight

Staphylococcus aureus in Frozen Dumplings

In November, media reported that frozen dumplings sold in the Mainland were removed from shelves after being found to contain the bacteria Staphylococcus aureus which raised public concerns.

Staphylococcus aureus is a bacterium that exists widely in our environment. It is commonly found in the nasal cavity, throat, hair and skin of healthy individuals and present in large numbers in wounds and infections. It can grow and multiply in food and eventually produce heat-stable toxins that cannot be destroyed by cooking. In general, Staphylococcus aureus population exceeding 100 000 per gram of food can produce sufficient toxin (about one microgram) to cause food poisoning. The onset of symptoms, which may include vomiting, diarrhoea and abdominal pain can be as soon as 30 minutes to eight hours after intake. These are usually self-limiting with most patients recovering within two days.

In Hong Kong, a set of Microbiological Guidelines for Ready-to-eat Food (Guidelines) stipulating the safety limits of major foodborne pathogens including Staphylococcus aureus has been developed by the Centre for Food Safety. Taking into account the level of Staphylococcus aureus needed to cause potential adverse health effects to consumers, the microbiological quality of a ready-to-eat food sample is considered unacceptable if it contains more than 10 000 Staphylococcus aureus per gram. Some other overseas countries such as the UK have also established similar safety level for Staphylococcus aureus in ready-to-eat food to ensure food safety. In case of food samples containing unacceptable levels of pathogens, apart from giving advice to the licensees of food premises, actions including issuing warning letters and other enforcement actions will be considered.

Food handlers should maintain good hygiene practices during food preparation and processing: always wash hands thoroughly with soapy water before and after handling foods, avoid handling cooked foods with bare hands, and stop handling foods when suffering or suspected to be suffering from infectious diseases. Raw or cold dishes should be kept at 4oC or below and hot foods at 60oC or above to prevent bacterial growth, and consumed as soon as possible.