food australia Journal, Vol. 74 (2) April - June 2022

FOOD SAFETY

Safe food: the role of handwashing and hygiene

Words by Deon Mahoney

Strategies to minimise contamination of our food supply by microbial hazards focus primarily on controlling raw materials and inputs, decontamination procedures, the application of kill steps and packaging. While these interventions represent the main ways of reducing the risk of foodborne illness for consumers, the importance of hygienic food handling practices and worker health and hygiene are often neglected.

Fortunately, the importance of effective handwashing has gained prominence with public health authorities in recent times, and no more so than during the COVID-19 pandemic. It is therefore timely to address worker hygiene practices and their role in advancing food safety.

Food handlers as sources of contamination

Humans are acknowledged as carriers of a wide range of microorganisms, both on the skin, in the nasal passages and in their intestinal tract. Many of these organisms are commensals, with little or no impact on the host. However, students of food microbiology are well versed in the risks presented by human carriers of an array of pathogens including Staphylococcus aureus, enteric pathogens such as non-typhoidal Salmonella spp. and Shigella spp., Clostridium perfringens, enteric viruses, and parasites which can be transmitted to food and infect consumers.

In addition to facilitating the spread of gastroenteritis, poor hygiene can result in the spread of respiratory illnesses.

While humans are capable of spreading a wide range of illnesses, there is only limited information available on the efficacy of handwashing to remove or eliminate pathogens.

The case of Typhoid Mary

Mary Mallon was an Irish immigrant who was a chronic, asymptomatic carrier of Salmonella Typhi. Mallon lived in New York and worked as a cook and laundress for wealthy families between 1906 and 1915. During that time, she was responsible for a series of outbreaks of typhoid fever infecting more than 50 people and causing three deaths. Concerns about the people infected with typhoid that followed in Mallon’s wake resulted in her being held in quarantine facilities in New York for much of her life. 1 Mallon’s story and her moniker Typhoid Mary continue to be used today as shorthand for a human vector of a communicable disease.

The extent to which foodborne pathogens are transmitted to food via handlers is not widely studied. Data on the transmission of illnesses from food handlers to restaurant patrons is relatively limited, and the view is that contemporary sanitation practices of food handlers probably helps prevent the spread of pathogens. But what is the likelihood of an infected food handler spreading pathogens to a food and causing an outbreak?

It is believed that the adoption of good personal hygiene practices including thorough handwashing can prevent an infected worker from transferring illnesses such as typhoid fever and hepatitis A to consumers. Recently there have been a series of hepatitis A outbreaks linked to food service workers in restaurants in the United States. This has led to the American personal injury lawyer and food safety advocate, Bill Marler calling for the Centers for Disease Control and Prevention to recommend all food handlers be vaccinated, because of the potential risk of spreading the virus to customers. 2 Hepatitis A is the only vaccine preventable foodborne illness.

Good hygienic practice requires food industry employees to absent themselves from work when unwell, particularly when they have gastroenteritis or skin infections. Unfortunately, not all people display symptoms of illness, yet they still shed infectious agents, potentially contaminating their hands, food, equipment and their surroundings.

While the focus is on food handlers in food businesses and the foodservice sector, there is also the issue of the way consumers handle food in the home and their food hygiene behaviours. This includes whether they wash their hands before and after handling raw foods such as meat, fish, poultry, produce and even eggs. Plus, there is the reality that home kitchens are normally not designed to hygienically handle food and minimise cross-contamination.

Studies of handwashing

Todd and colleagues published an important series of articles concerning food workers and foodborne illness, with a focus on situations where workers were implicated in the spread of foodborne illness. 3 In the series they considered outbreak investigation reports identifying the hands of food workers as the source of pathogens in specific outbreaks. They found that various activities result in workers hands quickly becoming contaminated, including touching raw materials and ingredients, the act of blowing the nose and using the toilet. The ninth article addressed the rationale for hand hygiene and the need for handwashing to remove as much soil as possible from the hands. 4

Not surprisingly, their findings demonstrated that food safety is improved by regularly removing as much soil as possible from workers hands. Suitable hand hygiene is achieved by regularly washing hands with good quality water and soap.The temperature of the water is not as important as the efficiency of the washing technique. Handwashing should be vigorous, with attention to all hand surfaces, with a minimum 20 seconds lathering with soap. This effectively removes pathogenic organisms from workers’ hands and reduces the risk of contaminated food. The emphasis then needs to be on providing facilities that enable effective handwashing: access to potable water, soap to aid removal of microorganisms, and disposable paper towels or air dryers to completely dry the hands.

It is highly desirable to use potable or treated water for handwashing. Typically, water used for handwashing should meet the microbiological standard of <1 E. coli/100ml. This can be problematic in remote areas, with some food producers in regional Australia unable to access water of such quality. This is a particular concern for the fresh produce sector where workers in the field often have limited access to water of satisfactory quality.

A recent study found handwashing with untreated, non-potable water, even if it contains low levels of indicator organisms, may provide a net reduction in faecal contamination on hands. 5 This has been interpreted to suggest that any water is better than none, but this is a false assumption. Contaminated handwashing water poses a risk of recontaminating hands with pathogens, presenting a significant source of infection risk.

This then leads to a discussion on the merits of using hand sanitisers where water quality may compromise the efficacy of handwashing in removing contamination. A 2020 study found hand washing with soap and water or a two-step alcohol-based hand sanitiser (ABHS) intervention performed similarly at reducing bacteria on farmworker hands. 6 The two-step ABHS procedure involves applying excess sanitiser to hands, its removal with paper towels, followed by a second application of sanitiser. The study also found the type of produce handled influences the ability of handwashing with soap and water or ABHS to reduce soil and contamination. This suggests the type of food or crop may need to be considered when developing hand hygiene interventions.

An earlier study found washing with soap, regular use of an ABHS, and a two-step ABHS intervention were all effective at reducing the concentrations of viable microbes on hands. 7 Importantly, the sanitiser based interventions were found to be effective hand hygiene solutions even on soiled hands.

In food production settings where the only water available in the field is irrigation water or surface water, the use of alcohol-based hand sanitisers is an effective adjunct to handwashing.

Hand sanitisers

Not all hand sanitisers are equal –avoid using general consumer handsanitisers as they are not suitablefor personnel working in the foodindustry. The Therapeutic GoodsAdministration provides guidanceon requirements for hand sanitisers:look for formulations that containa minimum of 60% ethanol orisopropyl alcohol, with no coloursor fragrances. The World HealthOrganization recommends that handsanitiser formula must contain 80%ethanol or 75% isopropyl alcohol.

Alcohol-based hand sanitisers are fast acting, rapidly and effectively inactivating a wide range of potentially harmful microorganisms on hands, but they are more effective if the hands are not visibly dirty or greasy.

Summary

Food producers and processors are increasingly expected to reduce food safety risks and implement systems that minimise incidents impacting the health of consumers as far as possible. Enhancing food safety does not involve seismic shifts in the way we produce, manufacture and prepare food. Instead, it encompasses small incremental improvements in general hygiene, starting with trained staff who consistently and diligently stick to hygienic procedures, including regular handwashing.

Effective handwashing is an essential life skill, protecting against an array of foodborne and respiratory illnesses. It assists in the removal of most transient contaminants and resident microorganisms from a food worker’s hands and exemplifies a basic strategy for supporting food safety across the entire food supply chain. Efficiency is facilitated by the simple physical action of washing, the use of soaps, drying the hands and the use of follow-on hand sanitisers.

References

1. Barr et al. (2021) The dangers of “Us versus them”: Epidemics then and now. Journal of General Internal Medicine, 36, (3): 795–796. https://doi.org/10.1007/s11606-020-06368-y

2. Marler, W. (2022) Platform: Message to Public Health – It is time, past time, to change views on hepatitis A vaccines for food handlers. Food Safety News

3. Todd et al. (2008). Outbreaks where food workers have been implicated in the spread of foodborne disease. Part 5. sources of contamination and pathogen excretion from infected persons. Journal of Food Protection, 71(12), 2582–2595. https://meridian.allenpress. com/jfp/article/71/12/2582/173013/Outbreaks- Where-Food-Workers-Have-Been-Implicated

4. Todd et al. (2010) Outbreaks where food workers have been implicated in the spread of foodborne disease. Part 9. Washing and drying of hands to reduce microbial contamination. Journal of Food Protection, 73 (10): 1937–1955. https://meridian. allenpress.com/jfp/article/73/10/1937/173301/ Outbreaks-Where-Food-Workers-Have-Been- Implicated

5. Verbyla et al. (2019) Safely managed hygiene: A risk-based assessment of handwashing water quality. Environmental Science and Technology, 53, 2852-2861

6. Prince-Guerraa et al. (2020) Both handwashing and an alcohol-based hand sanitizer intervention reduce soil and microbial contamination on farmworker hands during harvest, but produce type matters. Applied and Environmental Microbiology, 86, (18), 6:e00780-20

7. Fabiszewski de Aceituno et al. (2015) Ability of hand hygiene interventions using alcohol-based hand sanitizers and soap to reduce microbial load on farmworker hands soiled during harvest. Journal of Food Protection, 78, (11) 2024-2032

Deon Mahoney is Head of Food Safety at the International Fresh Produce Association.

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