Human Milk’s Hidden Gift: Implications of the Milk Microbiome for Preterm Infants’ Health

Abstract

Breastfeeding is considered the gold standard for infants’ nutrition, as mother’s own milk (MOM) provides nutritional and bioactive factors functional to optimal development. Early life microbiome is one of the main contributors to short and long-term infant health status, with the gut microbiota (GM) being the most studied ecosystem. Some human milk (HM) bioactive factors, such as HM prebiotic carbohydrates that select for beneficial bacteria, and the specific human milk microbiota (HMM) are emerging as early mediators in the relationship between the development of GM in early life and clinical outcomes. The beneficial role of HM becomes even more crucial for preterm infants, who are exposed to significant risks of severe infection in early life as well as to adverse short and long-term outcomes. When MOM is unavailable or insufficient, donor human milk (DHM) constitutes the optimal nutritional choice. However, little is known about the specific effect of DHM on preterm GM and its potential functional implication on HMM. The purpose of this narrative review is to summarize recent findings on HMM origin and composition and discuss the role of HMM on infant health and development, with a specific focus on preterm infants.

Lactobacillus commensals autochthonous to human milk have the hallmarks of potent probiotics

“…Choosing tertiary hospitals in major urban centres allowed a representative sampling of mothers who frequent them for obstetrical purposes [33]. Focusing solely on young, healthy peripartum mothers belonging to the same geo-ethnic mix increases the likelihood of obtaining beneficial commensals that are effective for that population [7, 24]. All of the LAB genera from human milk found in this study have been reported as pioneering colonizers of a healthy, breastfed infant gut [34].…”

“…The human colonic epithelial cell line, T84, was obtained from the Department of Medicine, UCSD, and cultured as described previously [7].…”

“…It appears at the onset of pregnancy and disappears with mammary involution [6]. Despite sharing similarities with the gut microbiota, it still has almost 300 unique bacterial species, which are not found elsewhere [7]. Streptococcal and staphylococcal species are the most abundant, followed by lactic acid bacteria (LAB) [8], and many strains belonging to different species have shown strong probiotic properties [9].…”

Host Factors of Favorable Intestinal Microbial Colonization

“…The origin of bacteria in human milk is not well-established. Two different routes, which are probably not mutually exclusive, have been proposed: (i) surface skin contamination and retrograde flow during breastfeeding and (ii) translocation through a more speculative gut-mammary route ( 153 ). The assumption that microbes in breast milk contribute to the establishment of the infant intestinal microbiome is supported by several studies in mother-infant pairs using sequencing techniques and demonstrating that breast milk and term infants' feces share specific microbial strains of Bifidobacterium, Lactobacillus, Enterococcus , and Staphylococcus ( 65 – 69 ).…”

Improving Breastfeeding by Empowering Mothers in Vietnam: A Randomised Controlled Trial of a Mobile App

“…A recent review confirmed the importance of breastfeeding in protecting against many infections; compared to infants given formula, there are significantly lower rates of diarrhoeal disease and lower respiratory tract infection, with a reduction of 50% or more to be expected, especially in infants under six months of age [ 11 , 12 ]. Exclusive breastfeeding is important for establishing a healthy microbiome, which has an important protective effect against chronic disease later in life, including obesity [ 13 , 14 , 15 ]. Children who had been breastfed for at least six months were less likely to be overweight or obese later [ 16 ].…”