Influence of milk product safety and household food hygiene on bacterial contamination of infant food in peri-urban Kenya

ABSTRACT Background Previous work in peri-urban communities within Kisumu County, Kenya, has shown that milk is a common weaning food and often contains enteric pathogens. Little is known about how milk and milk-based foods fed to infants become contaminated in peri-urban communities. Objective To compare the bacterial indicator and enteric pathogen detection levels in unpackaged, fresh pasteurized, and ultra-high temperature (UHT) treated milk at purchase, and assess its association with contamination of food prepared with this milk and fed to infants. Methods Paired samples of milk at point of sale and infant food prepared with this milk were obtained from 188 households enrolled as controls in the Safe Start trial. Samples were cultured to isolate Salmonella enterica, Shigella sonnei, Klebsiella aerogenes, Proteus spp., and E. Cole including Enterohemorrhagic (EHEC) E. coli 0157, with pathogens validated by PCR. Detection of these bacteria was compared across milk types, and between milk at purchase vs. point of infant consumption. Results Unpackaged milk was most contaminated at point of purchase, but bacterial contamination was also present in pasteurized and UHT milk. Presence of bacteria in milk at purchase predicted presence of the same bacteria type in infant food. Contamination detection frequency and concentration level for bacterial indicators generally increased between point of purchase and consumption among users of UHT and fresh pasteurized milk, but decreased among those using unpackaged milk. Detection of the four fecal bacteria in infant food was not significantly related to the type of milk used. Conclusion Kenyan infants are exposed to foodborne bacteria, including enteric pathogens, in milkbased foods. Both pre-market contamination and post-purchase handling influence the likelihood of milk given to infants being contaminated. Improvements in the safety of raw and pasteurized milk, and caregiver education on safe preparation and storage, are needed to reduce infant exposure to contaminated food. What is already known? Globally, food is an important cause of diarrheal outbreaks although evidence on the importance of food as a source of child exposure to diarrheal pathogen, and the source of those pathogens, in low income nations is scarce. While household hygiene influences infant food safety, consumption of pre-packaged foods, like pasteurized milk, have grown rapidly in recent decades, especially in urban populations, highlighting possible roles for both food systems and households in foodborne exposure of children. What are the new findings? Kenyan infants are frequently exposed to foodborne bacteria, including enteric pathogens, in milk-based supplemental foods. Pre-packaged pasteurized milk products are safer at point of purchase than unpackaged milk, although offered no protection for infants against bacterial exposure at point of consumption. Both purchased milk products and post-purchase household food handling behaviors influenced the likelihood of infant exposure to contaminated infant food. What do the new findings imply? Joint interventions targeting improvements in the safety of raw and pasteurized milk production, as well as caregiver education on safe preparation and storage of food, are needed for preventing foodborne exposure of peri-urban Kenyan infants.