Antibacterial properties of xanthine oxidase in human milk.

Formula-fed babies contract gastroenteritis more than breast-fed babies, which is of concern to mothers who cannot breastfeed or, as with HIV-infected mothers, are discouraged from breastfeeding. The ability of endogenous breastmilk xanthine oxidase to generate the antimicrobial radical nitric oxide has been measured and its influence on the growth of Escherichia coli and Salmonella enteritides examined. Breastmilk, but not formula feed, generated nitric oxide. Xanthine oxidase activity substantially inhibited the growth of both bacteria. An important natural antibiotic system is missing in formula feeds; the addition of xanthine oxidase may improve formula for use when breastfeeding is not a safe option.