Preventing Foodborne Staphylococcal Disease

Although meat products are an important source of foodborne disease caused by Staphylococcus aureus, Kadariya et al. (2014) note that other foodstuffs such as sandwich fillings, bakery goods, salad items and dairy can also transmit this microbe. Since contamination mostly arises opportunistically from improper handling practices in the retail food chain, producers can take steps to prevent consumer illness by paying attention to HACCP (Hazard Analysis and Critical Control Points) policies and implementing routine food hygiene policies.

Staphylococci are rounded Gram positive bacteria frequently seen under microscope as clusters. One species, Staphylococcus aureus is ubiquitous, being found in the environment and as commensals in the human respiratory tract. As commensal microbes, staphs, as they are commonly known, do not usually cause problems. However, under favorable conditions S. aureus colonizes foodstuffs and produces various enterotoxins that persist in the product. Ingestion of foods contaminated with these heat-tolerant entertoxins cause acute, rapid onset enteric disease. Symptoms such as nausea, vomiting and stomach cramps usually appear within 3-5 hours of eating only a low dose of the enterotoxin.

Although staphylococcal contamination of raw ingredients such as milk can happen, most foodborne illness comes from eating foodstuffs infected during preparation. A combination of unhygienic handling, inadequate preparation and processing, and poor storage give just the right conditions to allow staph colonization and enterotoxin release. As Kadariya et al. review, there are a number of steps in the food safety HACCP control path that producers can use to keep consumers safe.

Key Risk Factors for Staphylococcal Contamination:

Handling:
Incorrect handling practices are a common cause of foodborne staphylococcal infection. Since the microbe is ubiquitous and carriers may not show symptoms, staff should be diligent about regular hand washing, in addition to replacing gloves frequently. Management should ensure that workers carry out both of these two practices, since one does not replace the other and may in fact make the risk of contamination worse.
Processing and Preparation:
When preparing and processing foodstuffs, workers must stick closely to the prescribed protocols, ensuring correct temperatures and cooking times, plus adequate cooling and cold temperature storage. In general, this means heating to above 60°C and chilling below 5°C. Kitchen and serving staff should pay attention to hot holding, reheating and prolonged maintenance at room or outdoor temperatures to reduce risks. Staff must also prevent cross contamination and maintain workplace hygiene.
Raw Ingredients:
In addition to steps taken by food industry managers, Kadariya et al. also note that control measures on the farm are important steps in keeping staphylococcal contamination under control. Mastitis control is important on dairy farms since both methicillin-susceptible and methicillin-resistant (MRSA) S. aureus can cause mastitis in cows. Removing infected cows or treating them promptly prevents bulk tank contamination. Raw meats can also be infected with S. aureus during slaughter and processing, either through contamination with gut contents or from workers themselves.

As a final summary of control measures, Kadariya et al. stress the importance of maintaining the cold chain to prevent staph colonization and enterotoxin contamination.

Learn more about the Staphylococcus aureus group and a HACCP approach to food safety in our food and beverage community

Reference

1. Kadariya, J. et al. (2014) “Staphylococcus aureus and Staphylococcal Food-Borne Disease: An Ongoing Challenge in Public Health“, BioMed Research International 827965 http://dx.doi.org/10.1155/2014/827965