Behaviour and cross-contamination of pathogenic bacteria in household kitchens - relevance to exposure assessment

Illness resulting from consumption of contaminated food is a continuous serious public health problem in the world. A proportion of this foodborne disease is attributable to improper preparation practices in the home, including cross-contamination.

Salmonella , Campylobacter and Staphylococcus aureus survive on stainless steel surfaces for hours or days, depending on the species, initial counts and the presence of food residues. Following a single contamination and air-drying at room temperatures, pathogenic bacteria also remain on cleaning sponges for days, with or without the presence of food residues. The exposure to low water activity surfaces induces filamentation of Salmonella cells, some of which reach a size of 50 µm or more. Filamentous cells maintain their membrane integrity for days on these surfaces and are able to split in single cells under favourable conditions, resulting in the instantaneous appearance of a large number of viable cells.

Considering the common practice of surface cleaning, wiping countertops and other kitchen surfaces reduces microbial counts considerably, particularly when a clean cloth or an antibacterial-impregnated napkin is used. On the contrary, when the cloths are damp and contain high numbers of microorganisms, bacteria are readily spread from the cloths to the surfaces instead of removing bacteria from the surfaces.

Pathogenic bacteria survive the treatments with antibacterial dishwashing liquid in sponges. Furthermore, to reduce the count numbers of Salmonella and S. aureus in cloths a higher concentration of household bleach is needed than that in a suspension. Presence of food debris in the cloths, which occurs regularly in practical situations, decreases the effectiveness of antibacterial compounds or disinfectants. Therefore, other measures, such as heating, i.e. immersing in boiling water or washing by a dishwash or laundry cycle with detergents at > 60 ^oC is suggested to reduce bacterial contamination in cloths.

A quantitative analysis on cross-contamination of Salmonella and Campylobacter from contaminated chicken carcass to salad via kitchen surfaces has shown that it is realistic to expect that a proportion of the human exposure to, particularly, Campylobacter originates from cross-contamination in private kitchens during food handling. The probability that salads become contaminated with Campylobacter is higher than that with Salmonella since the prevalence and the levels of Campylobacter on chicken carcass are higher than that of Salmonella .

As foodborne disease occurrence continues over time, prevention and control measures must be managed on a continuous basis. Each individual contributes a critical role in preventing and controlling illness. Basic personal and kitchen hygiene can greatly help to defend against harmful microorganisms.