Effects of Lactobacillus fermentum CECT5716 Lc40 on infant growth and health: a randomised clinical trial in nursing women

The breast milk microbiota has been described as a source of bacteria for infant gut colonisation. We studied the effect of Lactobacillus fermentum CECT5716 (Lc40) on growth and infection incidence of the infants, when the probiotic is administrated to the mothers. Moreover, whether such effects might depend on the interaction between the mother or infant microbiota and the probiotic administration. A total of 291 mother-infant pairs were studied for 16 weeks in a randomised double-blinded placebo-controlled multicentre trial. The Lc40 group (n=139) received 1 capsule/day containing 3x 10(9) cfu Lc40; the control group (n=152) received 1 placebo (maltodextrin) capsule/day. A positive and significant correlation of the Staphylococcus load between breast milk and infant faeces was only observed in control group. Additionally, the weight z-score of the infants whose mothers had higher values of Lactobacillus in their breast milk were significantly higher for the Lc40 group. We observed a significant lower incidence of conjunctivitis in the infants whose mothers received Lc40. A higher load of Staphylococcus in infant faeces significantly increased the risk of respiratory infections. Such incidence, under an absent or low Staphylococcus load in the faeces, was significantly 36 times higher in the infants in the control group than in the infants in the Lc40 group. However, the protective effect of Lc40 was gradually reduced as the Staphylococcus load of the milk increased. The administration of Lc40 to nursing women might influence infant growth and health but it seems to depend on its interactions with mother or infant microbiota.