A group of Swedish researchers have carried out a study (which is freely available online, thank you authors) to find out how babies’ guts are colonized with microbes, and their findings make for fascinating reading.
The researchers began from the premise that, “From an ecological point of view, colonization of the infant’s gut represents the de novo assembly of a microbial community (Costello et al., 2012) and is influenced by dietary and medical factors (Eggesbø et al., 2011, Koenig et al., 2011, La Rosa et al., 2014). However, it is not clear how these factors contribute to the overall composition and function of the infants’ gut microbiome, and how different microbes cooperate or compete with one another as the gut environment changes.” (Bäckhed et al 2015: 690).
In order to explore this, they looked at 98 full-term babies and their mums, analysing stool samples at several points throughout the first year of the babies’ lives. They summarised their findings as follows:
“In contrast to vaginally delivered infants, the gut microbiota of infants delivered by C-section showed significantly less resemblance to their mothers. Nutrition had a major impact on early microbiota composition and function, with cessation of breast-feeding, rather than introduction of solid food, being required for maturation into an adult-like microbiota. Microbiota composition and ecological network had distinctive features at each sampled stage, in accordance with functional maturation of the microbiome. Our findings establish a framework for understanding the interplay between the gut microbiome and the human body in early life.” (Bäckhed et al 2015: 691).
In other words: the babies who were born vaginally and who were exclusively breastfed ended up with microbiota which resembled those of their mothers. The microbiomes of babies who were born by caesarean or who were fed formula milk showed a very different development – which is illustrated really well on a picture available in the article itself.
To give a bit more detail on some of the key points, these were a few of the lines and paragraphs that particularly got my attention:
- “Compared with vaginally born infants, the C-section fecal microbiome was enriched in MetaOTUs such as Enterobacter hormaechei/E. cancerogenus, Haemophilus parainfluenzae/H.aegyptius/H. influenzae/H. haemolyticus, Staphylococcus saprophyticus/S. lugdunensis/S. aureus, Streptococcus australis and Veillonella dispar/V. parvula, indicating that skin and oral microbes, but also bacteria from the surrounding environment during delivery, were the first colonizers in these infants. In contrast, the gut microbiota of vaginally delivered newborns were enriched in microbes from the genera Bacteroides, Bifidobacterium, Parabacteroides, Escherichia/Shigella (p < 0.05), which also were the most abundant members of the newborns’ gut microbiota.” (Bäckhed et al 2015: 691).
- “Mother-to-infant transmission was compromised in C-section-delivered neonates.” (Bäckhed et al 2015: 693).
- “Our results indicate that most of the early colonizers of the newborn gut originate from the mother and that the mode of birth is an important factor shaping the gut microbiota of term infants in early life.” (Bäckhed et al 2015: 694).
- “The gut microbiome is an important producer of vitamins (Figures 3A, S3G, and S3H). All newborns in Sweden receive prophylactic vitamin K injections to avoid classic hemorrhagic disease. We observed enriched levels of genes for vitamin K2 (menaquinone) synthesis in newborns, which correlated with the high abundance of Bacteroides and Escherichia/Shigella (Table S4), known vitamin K2 producers (Wang et al., 2013).” (Bäckhed et al 2015: 694). (And yes, I’ll almost certainly be looking at that in more depth sometime!!)
- “At 4 months, we noted clear differences between infants who received exclusive breast-feeding and exclusive formula-feeding … our results underscore the role of breast-feeding in the shaping and succession of gut microbial communities during the first year of life.” (Bäckhed et al 2015: 697).
- “The microbiome of infants delivered by C-section … tended to contain a greater portion of antibiotic resistance genes compared to vaginally delivered infants…” (Bäckhed et al 2015: 694).
I am left with a couple of questions. Firstly, I didn’t spot anything telling us where the babies were born, or which suggested that the authors had considered place of birth as a potentially significant factor in this study. I suspect that these babies were all born in hospital, but it would be good to see the results of a similar study which looked at different locations for birth and considered whether there were differences in babies born at home, in birth centres or in hospitals, or whether the immediate environment (that is, the body of the baby’s mother and/or anything which gets in between mother and baby) overrides the potential impact of the wider environment.
It would also have been good to know more about the impact of antibiotics on the development of babies’ microbiomes, especially as these are so frequently used in modern maternity care. But I do appreciate that the authors have already given us loads of new and brilliantly useful information and that Rome wasn’t built in a day! I hope that we will see more studies like this over the coming months and years, as they teach us so much about what is important and about how we can best protect the normal development and good health of future generations.