Calhau Lab | The in utero microbial colonization hypothesis

Juliana Morais, from ProNutri Lab, led by Conceição Calhau, recently published an article in the journal Gut Microbes entitled "Extremely preterm neonates have more Lactobacillus in meconium than very preterm neonates - the in utero microbial colonization hypothesis"

In brief, Juliana Morais talks about this article:

What discoveries led you to the research described in your publication?
The dogma between the “sterile uterus” and “colonization in utero” hypothesis is over 100 years old. However, growing evidence shows the presence of bacteria DNA in the amniotic fluid, placenta and meconium, which somehow support the intrauterine microbial colonization hypothesis.

What were you trying to understand and what is the main discovery of this work?
This work integrates a mother-infant birth cohort – FEEDMI (NCT03663556) – that aimed to evaluate the influence of different types of infant-feeding on the preterm infants’ gut microbiota and the influence of vertical microbiota transmission. In addition to the results that associate the newborns’ feeding practices at neonatal intensive care unit and their intestinal microbiota (unpublished results), the results addressing the in utero colonization hypothesis, showing that extremely preterm neonates (< 28 weeks of gestation) have more Lactobacillus than very preterm neonates (28 - 32 weeks of gestation) regardless of the mode of delivery, were remarkable.

Why is this important?
Understanding the role of intrauterine environment on fetal microbiota colonization, as well as the impact of very early postnatal factors on infants’ microbiota, is the key step for bacterial modulation through clinical interventions such as maternal diet, exposure to antibiotic, probiotics and prebiotics, or even fecal transplantation. This individual-specific modulation will promote health and reduce the chronic disease in adult life. Specially among the preterm infants, where it is observed a delay and immature gut microbiota, higher levels of oxidative stress and inflammation, they surely would benefit from these interventions.

Can you use an analogy to help us understand your work?
Like Planet Earth, the human gut is an ecosystem that contemplates life in different forms. With the knowledge about the role of microorganisms in our Planet, it is now possible to take advantage of its biological and energetic resources and, thus, to know life as it is today. The greater the knowledge about the microorganisms in the human gut (what they produce, how they interact with each other and with the host), the greater the advantage we can take from our gut microbiome. In the case of intestinal microbial colonization, understanding how bacteria reach the fetus intestine is to better understand human physiology, in order to optimize medical and nutritional interventions.

What questions remain to be asked?
The results published in this work demonstrated that mother-to-infant bacterial transmission is a controlled and time-specific process. However, the question that remains open is: what is the impact of this early colonization in short (development of necrotizing enterocolitis) and long term (development of autoimmune or other chronic non-communicable diseases) and how is this influence of maternal antepartum factors (dietary pattern, pre-gestational body mass index, antibiotic therapy)?

Read the full article here.

Figure 4 from the article | "Controlled and time-specific mother-to-infant bacterial transmission: (a), the vertical bacterial transmission starts mainly with Lactobacillus (predominantly from vaginal microbiota) via the vaginal ascending route; (b), during the third trimester, maternal gut bacteria is predominantly transmitted to the fetus intestine via the hematogenous route and through deglutination of amniotic fluid"

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