Inhibition of enteropathogenic bacteria by human milk whey in vitro

Diarrhea caused by enteropathogenic bacteria is a leading cause of childhood mortality world-wide, particularly in less developed regions. Breast-feeding has been advocated to protect infants and children from infectious illnesses. We examined the antibacterial activity of human whey in vitro against multiple strains of the following species of enteropathogenic bacteria, Campylobacter jejuni, Escherichia coli, Salmonella typhimurium, Shigella flexneri, Shigella sonnei and Vibrio cholerae, all isolated from humans with diarrheal illness. In vitro human whey inhibited the growth of most but not all of the enteropathogenic strains tested. The test strains multiplied in both bacterial growth medium and commercial infant-feeding formula controls, with the exception of the Campylobacter strains, which were markedly inhibited in formula. These results confirm and extend previous observations that human whey contains components capable of inhibiting enteropathogenic bacteria and which may be associated with the protective effects of breast feeding. The precise mechanisms of these inhibitory effects merit further study.