Quantification and variability of Escherichia coli and Staphylococcus aureus cross-contamination during serving and consumption of cooked thick porridge in Lungwena rural households, Malawi

The study investigated bacterial transfer to cooked thick porridge via ladles and hands during serving in 29 households in Lungwena, rural Malawi. Household stored water used for hand and ladle washing, was contaminated with Escherichia coli and Staphylococcus. aureus from hands of members of the household or from contaminated ladles used in food preparation. The results showed that hands became contaminated with E. coli and S. aureus cells in the range 0.6–3.7 and 2.2–4.3 log10 CFU/cm2, respectively, following washing with the contaminated water. Ladles became contaminated with 0.9–3.2 log10 CFU/cm2 of E. coli cells whereas contamination with S. aureus on ladles ranged between 1.9 and 4.6 log10 CFU/cm2. Bacterial transfer from hands to food ranged from <1 to 3.6 log10 CFU/g for E. coli and 2.1 to 4.2 log10 CFU/g for S. aureus. Ladle surfaces transferred from 1.3 to 3.1 and from 1.2 to 4.3 log10 CFU/g of E. coli and S. aureus, respectively, on to the food. Contamination of food by hands was significantly (p < 0.05) higher than that of ladles and transfer of S. aureus was significantly (p < 0.05) higher than that of E. coli. The amount of bacteria transferred to the recipient depended on the wash water type and bacteria type. The study has demonstrated that although the traditional cooking of thick porridge inactivates S. aureus and E. coli, the porridge can be contaminated with bacteria during consumption using hands and serving on to a plate with wooden ladles.