 Human milk is the sole source of nutrition for infants during the first weeks to months after birth, and has evolved to provide nutrition and immunological protection in the extra-uterine environment into which the infant is born. But when breastfeeding is not possible, human newborns may circumstantially be fed with infant formulas. The difference of feeding mode has been demonstrated to have a strong influence on early gut colonization particularly on the probiotic bacteria. Studies show that breastfed infants have higher counts of Bifidobacteria and Lactobacillus and lower counts of Bacteroides, Clostridium, coccoides group, Staphylococcus, and Enterobacteriaceae as compared with formula-fed infants. 