Home Hygiene & Health
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Aug 20th: Spread of foodborne contamination in domestic kitchens and hygiene practices of older adults

Illness from foodborne pathogens such as Campylobacter spp., Clostridium perfringens, Escherichia coli, Salmonella spp. and Staphylococcus aureus is reported to be greater among older adults than in the general population. Research also suggests older adults’ inadequate knowledge and negative attitudes toward food hygiene may increase implementation of unsafe food practices.

This new study aimed to determine microbiological contamination of domestic kitchens of older adults. Food contact surfaces and equipment (1,292 samples) in 100 domestic kitchens of older adults (>60 years) were analyzed to isolate aerobic bacteria, Enterobacteriaceae, Staphylococcus aureus, and Listeria spp. Self-reported hygiene practices were also recorded.

Highest contamination levels were determined on in-use cleaning equipment (dish brushes, dishcloths, sponges) with aerobic bacteria, 9.3 log CFU per item, Enterobacteriaceae, 8.8 log CFU per item, and S. aureus, 7.0 log CFU per item. Results indicate that cleaning equipment plays a significant role in spreading contamination to kitchen surfaces.   Positive correlations were found between aerobic bacteria on dishcloths and multiple surfaces in the domestic kitchen, including the refrigerator door handle, worktop surface, raw meat shelving area, bin lid, and the chopping board. Similarly, positive correlations were found between S. aureus contamination  on dishcloths and kitchen surfaces, including refrigerator door handle, hot water tap handle, sink basin, hand towel, worktop counter surface, and the raw meat shelving area,

Ninety-six percent of domestic kitchens had one or more site contaminated with Enterobacteriaceae, the most frequently contaminated domestic kitchen items being dish brushes (95%) and dishcloths or sponges (88%) contaminated with 8.8 log CFU per item. These high levels suggest that microbes were multiplying in the moist conditions which the cloths etc provide to form a permanent reservoir of contamination. What is not known is whether these spp were free living, or strains of human or animal origin, and whether any of the isolates were potentially pathogenic

Thirty percent of domestic kitchens had one or more sites contaminated with S. aureus. Perhaps surprisingly, since the S aureus is most likely to be of human origin, although the most frequently contaminated items were dishcloths or sponges (11%) and dish brushes (13%), but only 8% of hand towels were found to be contaminated.  What is surprising is the high levels (102 up to 106 per sample area) of S aureus which were found particularly on cleaning utensils. This is surprising because S aureus would not be expected to multiply on inanimate surfaces.

Listeria spp. were isolated from single sites in 7 kitchens. L. monocytogenes was isolated from a single hand contact surface in 2% of kitchens (a refrigerator door handle and a hot water tap handle). The conditions of the locations that were isolated with L. monocytogenes were both dry at the time of the home kitchen survey but there was some visible food debris present on both hand contact sites. Isolation of L. monocytogenes from domestic kitchens of older adults in this study concur with previous studies of domestic kitchens whereby L. monocytogenes was not commonly isolated. The researchers concluded that storage practices are the greatest risk factor for listeriosis.

Reported usage length of dish brushes was significantly correlated with Enterobacteriaceae contamination. Significant correlations were determined between contamination and reported cleaning frequency of refrigerators. Contamination of hand towels in single-occupant households was significantly greater than in multioccupant households. The authors conclude that there is a need for older adults to improve food hygiene practices in the domestic kitchen.

Evans EW, Redmond EC. Domestic kitchen microbiological contamination and self-reported food hygiene practices of older adult consumers. Journal of food protection. 2019 Jul 17;82(8):1326-35.