An unidentified substance in human milk that promotes the growth of Lactobacillus bifidus in an infant's stomach is responsible for the so-called bifidus factor. Once this innocuous bacterium populates a breast fed child's digestive tract it excretes lactic acid as a waste product, thus inhibiting the growth of harmful microbes that could affect the infant once away from the protective environment of the womb.
Maybe this is where Nestle got it wrong?