Abstract
The maternal gut is the principal source of commensal bacteria in the infant gut during the lactation stage, where breast milk acts as an intermediary for the transfer of potential probiotic bacteria consortia, including Lactobacillus. This study aimed to characterize the bacterial communities in human milk, maternal, and infant feces in a small yet very homogeneous cohort of 25 healthy mother–infant pairs in northwestern China (n = 25, infant age from 7 days to 2 years), with special emphasis on the cooccurrence and vertical transfer of Lactobacillus phylotypes at the species or strain level in mother-breast milk-infant triads. Accurate sequencing analysis revealed that among 73 Lactobacillus zero-radius operational classification units (ZOTUs) identified, 58 belonging to 18 recognized species or species groups were distributed in all three types of samples. Lactobacillus ruminis, L. mucosae and L. gasseri-johnsonii as true residents were the most represented in all three ecosystems, whereas the content of Lactobacillus phylotypes commonly developed as probiotics was not dominant. While the numbers of Lactobacillus species in breast milk and infant feces were greater than that in maternal feces, principal coordinates analysis (PCoA) based on beta diversity, coupled with the frequency of isolates determined by culture methods, showed that the Lactobacillus community in the infant gut was more similar to that in the maternal gut than to that in breast milk, suggesting that the gut is niche selective for Lactobacillus populations. In addition, identical strains of L. ruminis, L. paracasei, L. mucosae and L. salivarius were isolated from multiple mother–infant pairs, supporting the hypothesis that vertical transfer of bacteria via breastfeeding contributes to the initial establishment of the microbiota in the developing infant intestine.
Highlights
The human gut microbiota establishment and formation in the first 1,000 days of life play an irreplaceable role in the long-term health and well-being of the host (Matamoros et al, 2013; Marchesi et al, 2016)
It has been increasingly considered that the maternal gastrointestinal tract is the principal source of microorganisms in breast milk (York, 2018), and there is a consensus that breast milk acts as an intermediary for the transfer of functionally important bacteria from mother to infant, especially for potential probiotic bacteria, such as members of Lactobacillus and Bifidobacterium that can colonize the infant gut (Martín et al, 2007, 2010; Solís et al, 2010; Mikami et al, 2012; McGuire and McGuire, 2017)
Bacteria that relocate from the birth canal during parturition and from breast milk during lactation affect the colonization of gastrointestinal microorganisms in newborns (Funkhouser and Bordenstein, 2013; Verdu et al, 2015; Martin et al, 2016)
Summary
The human gut microbiota establishment and formation in the first 1,000 days of life play an irreplaceable role in the long-term health and well-being of the host (Matamoros et al, 2013; Marchesi et al, 2016). Lactobacillus Populations in Mother-Breast Milk-Infant Triads that breast milk provides infants with nutrients necessary for growth and development, and contains lactoferrin, breast milk oligosaccharides, immune cells, regulatory cytokines, and other biologically active factors, creating a favorable environment for the colonization of beneficial bacteria in the gut of newborns (Walker, 2010; Jeurink et al, 2013; Mastromarino et al, 2014; Praticò et al, 2014; Cacho and Lawrence, 2017) It has been controversial whether milk bacteria play a role in seeding the infant gut and the origins of bacteria in human milk. It has been increasingly considered that the maternal gastrointestinal tract is the principal source of microorganisms in breast milk (York, 2018), and there is a consensus that breast milk acts as an intermediary for the transfer of functionally important bacteria from mother to infant, especially for potential probiotic bacteria, such as members of Lactobacillus and Bifidobacterium that can colonize the infant gut (Martín et al, 2007, 2010; Solís et al, 2010; Mikami et al, 2012; McGuire and McGuire, 2017)
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