The need for consumer food safety in the home

Foodborne disease incidence associated with the home
Sources of food contamination are diverse and foodborne pathogens associated with a range of raw foods are regularly brought into the domestic kitchen. Transmission of such pathogens to humans, due to implementation of unsafe food-handling behaviours within the household, is seen as inevitable. The domestic kitchen has been described as the “front line in the battle against foodborne disease” (CFIA, 1998). Foodborne illnesses most often arise from the handling and preparation of food and it is reported that a substantial number of cases of foodborne disease occur in the home (POST, 1997). Catering premises are subject to food legislation specifying design, layout, construction and size requirements, and food handlers go through food safety training. However, the domestic environment may have inadequate facilities for equivalently safe food preparation, as consumers have no formal training and no food safety regulations apply to the home unless it’s being used for commercial processes. So it is possible to see how foodborne outbreaks may originate when food is prepared and served at home (Ryan et al., 1996).

Reported incidence of foodborne disease associated with the domestic environment in the UK, Europe, USA, Canada, Australia and New Zealand is variable and is based upon reported outbreaks. Outbreaks of foodborne illness occurring in private homes are less likely to be reported than those in commercial and public premises (Scott, 2003). Given the substantial under-reporting of foodborne disease and the fact that the majority (more than 95%) of foodborne disease cases are thought to be sporadic (FSA, 2000) and less likely to be investigated by public health authorities, the actual proportion of foodborne disease cases that occur in the home is likely to be much greater than reported outbreak data suggests (Redmond & Griffith, 2003). Nevertheless, data from England, Wales, USA and Canada suggest between 12 and 20% reported foodborne outbreaks have been attributed to the home. Data from Australia and New Zealand suggest between 20 and 50% of foodborne illness has been attributed to the home and data for some European countries suggest that up to 95% of reported foodborne disease outbreaks have been associated with food prepared or consumed in the home. In Europe, FAO/WHO (2002) stated that the “private home is the single location where most foodborne outbreaks occur”. Throughout Europe the frequency distribution of the places where outbreaks occurred varies from country to country, depending on differences in eating habits.

Bacterial contamination and the domestic kitchen
Potential pathogens can enter the domestic kitchen via a variety of routes, for example, raw foods. Poultry is acknowledged as an important potential reservoir of foodborne pathogens, particularly Campylobacter and Salmonella species (ACMSF, 1996). Microbiological surveys of raw, retail poultry have identified high prevalence rates (Harrison et al., 2001) and it is clear that poultry meat continues to be a significant route for the transmission of Campylobacter and Salmonella – the leading causes of bacterial gastroenteritis in humans – in industrial, domestic and catering environments. Campylobacter is known to be a primary cause of sporadic cases of foodborne illness (Tam, 2001) and the annual number of reported cases exceeds reported Salmonella cases in many European countries (Takkinen & Annon, 2003). A study that evaluated the acute health effects and risks associated with different foods, showed that chicken was associated with relatively high levels of risk and accounted for more disease, health service usage and death than any other individual food type (Adak et al., 2005). The largest proportions of reported foodborne disease outbreaks associated with the private home have been caused by Salmonella (Tirado & Schmidt, 2000). However, as the incidence of Campylobacter is mainly sporadic it is possible that more cases of Campylobacter infection may be attributed to the home than Salmonella. Food is not the only route or vehicle by which microorganisms can enter the kitchen. The presence of soiled laundry and pets is not uncommon and the domestic kitchen has been used for motor vehicle maintenance, gardening and even breeding chickens – each use bringing its own microbiological hazards (Worsfold & Griffith, 1997). So, the multifunctional nature of the modern kitchen directly impacts upon the need for better food safety in the home (Scott, 2003).

The importance of the home as a location for acquiring foodborne disease has prompted the assessment of levels of bacterial contamination within the domestic environment. Other studies have quantified bacterial pathogens in the home and determined the effectiveness of cleaning agents and methods. However, few surveys have evaluated microbial contamination in the domestic kitchen after food preparation. Most studies have concluded that the domestic environment is an important source of foodborne infections, and hygiene behaviour and/or cleaning practices need to be improved to reduce levels of contamination in the domestic environment.

Research results have shown that the majority of domestic environments were contaminated with pathogenic and non-pathogenic microorganisms. Interestingly, two studies found bacterial contamination levels in kitchens to be higher than in bathrooms (Ojima et al., 2002). Finch et al., (1978) reported that the normal domestic environment appears to support a fairly wide range of bacterial species and Josephson et al., (1997) concluded that normal kitchens can be easily contaminated with a variety of bacterial contaminants including faecal coliforms, Enterobacteriaceae (such as E. coli), Campylobacter spp. and Salmonella spp.. Campylobacter spp. have also been detected from commercial and domestic kitchens after food preparation (Dawkins et al., 1984; Redmond et al., 2004). Listeria spp. (including Listeria monocytogenes) has been isolated from 20% of domestic kitchens (Cox et al., 1995), and from 47% of kitchens and bathrooms (Beumer & Kusumaningram, 2003) and both studies expressed concern for the implications of human exposure to these pathogens in the domestic environment. Other organisms that have been detected in the domestic environment include Staphylococcus spp. (Josephson et al., 1997; Spiers et al., 1995; Finch et al., 1978), Bacillus spp. and Micrococcus spp. (Finch et al., 1978; Scott et al., 1982; Speirs et al., 1995), and Streptococcus spp. (Scott et al., 1982). It has also been reported that potentially pathogenic E. coli, Klebseiella pnneumoniae, and Enterobacter cloacae are the most frequently detected species in the home (Scott et al., 1982).

Cronobacter spp. (formerly Enterobacter sakazakii) have also been isolated from the home environment (Kandhai et al., 2004). These organisms are a relatively rare, but often fatal, cause of infection in neonates that has resulted from consumption of contaminated powdered formula milk. A review of cases and outbreaks of Cronobacter spp. infection has found that these bacteria were isolated from food/formula preparation items such as blenders, bottle cleaning brushes and spoons (Muytjens & Kollee, 1990).
The type and density of bacterial contamination is influenced by the physical nature of the site sampled (Gorman et al., 2002). Contaminants detected from the majority of studies were more commonly isolated from wet or moist locations (Cox et al., 1995; Josephson et al., 1997; Scott et al., 1982; Speirs et al., 1995) where survival and proliferation of organisms is favoured. The most common locations of heavy contamination in the domestic kitchen are dishcloths, cleaning cloths, sponges, sink environments and towels (Beumer & Kusumaningram, 2003; Cox et al., 1995; Finch et al., 1978; Josephson et al., 1997; Scott et al., 1982; Speirs et al., 1995). Kitchen sponges and dishcloths are considered to be particularly conducive for growth and survival of bacteria as they are continuously moist and supplied with nutrients in the form of food scraps and organic matter (Doyle et al., 2000). Other contaminated locations include those frequently touched, such as taps and fridge handles. These findings suggest that these locations may not just harbour the bacteria, but also spread them around the kitchen during use (Doyle et al., 2000; Scott et al., 1982; Redmond & Griffith, 2005). So, it is suggested that consumers use disposable paper towels for cleaning surfaces in the kitchen, rather than dishcloths.

There are inherent problems with these types of study, which may underestimate the presence of pathogens, including the random nature of the sampling, irrespective of the types of foods prepared. This may be compounded by relatively low numbers of pathogens in relation to non-pathogens, coupled with overgrowth of the latter. Other studies (Haysom & Sharp, 2005) have attempted to monitor trends in kitchen site microbial contamination over time, where contamination was seen to peak after meal preparation (although other non-food preparation activities also contributed). Research studies starting with an uncontaminated kitchen, showed how contamination of specific sites with food pathogens was found to occur during food preparation (Redmond et al., 2004). Contamination and recontamination of sites in the domestic kitchen is constantly changing and coupled with poor general design, construction, maintenance and cleaning when compared to food processing plants, it is easy to see how the domestic kitchen could be a factor in domestic foodborne disease.

During food preparation, pathogens such as Campylobacter, Salmonella, E. coli and Staphylococcus aureus are spread from infected foods such as raw chicken to contact surfaces in the domestic kitchen (Gorman et al., 2002), increasing the potential risk for foodborne disease. Laboratory experiments have shown that both Campylobacter and Salmonella can be easily transferred from raw chicken products to kitchen surfaces and hands (De Boer & Hahne, 1990) and dissemination of such pathogens to hands, cloths and hand- and food-contact surfaces during preparation of a chicken meal has previously been demonstrated (Redmond et al. 2004). Campylobacter and Salmonella can persist on surfaces and this may lead to an increased risk of cross-contamination between food handlers, ready-to-eat (RTE) foods and other food contact surfaces. This not only presents contamination risks within the preparation of one meal (intra-meal contamination), but also between different meals (inter-meal contamination).

Consumer food safety
Consumers are the important final link in the food chain to assure safe food consumption and prevent subsequent illness (The Pennington Group, 1997). Consumers have responsibilities as purchasers, storers, providers and processors of food and need to be conscious of the nature and safety of food products. Food-handling practices employed by consumers in the domestic kitchen influence the risk of pathogen survival and multiplication, as well as cross-contamination to other products. Using observation and microbiological risk assessment, consumer food safety is needed to inform risk communication strategies to increase consumer implementation of risk-related practices and reduce the risk of foodborne disease.

Elizabeth C. Redmond and Christopher J. Griffith (Food Research and Consultancy Unit, University of Wales)

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