Are there really bacteria in the womb?
A new study has refuted scientific claims that babies harbour bacteria while still in the womb. Supported by nine EU-funded projects (Homo.symbiosus EarlyLife, Lacto-Be, BEHAVIOME, MetaPG, microTOUCH, ONCOBIOME, MASTER and IHMCSA), the research revealed flaws in the concept of a foetal microbiome and concluded that bacteria detected in foetal tissues originate from contaminated samples taken from the uterus. The research findings have been published in the journal ‘Nature’. Claims that the human foetus, placenta and amniotic fluid are colonised by microbial communities in a healthy pregnancy remain a subject of debate. As reported in a news item posted on ‘SciTechDaily’, if true, this would not only seriously impact clinical medicine and paediatrics, it would also undermine established principles in immunology and reproductive biology. The inaccurate belief that there is a foetal microbiome may therefore have hindered research progress, according to researchers from MASTER and IHMCSA project partner University College Cork (UCC), Ireland.
Healthy equals sterile
To investigate these claims of a foetal microbiome, study senior author Prof. Jens Walter of UCC brought together experts in reproductive biology, microbiome science and immunology from across the globe. After assessing possible mechanisms by which the foetus might interact with microorganisms, the team found that a healthy human foetus is in fact sterile. Any microbiomes found in foetal tissues are the result of contaminated samples taken from the womb, with the contamination occurring during vaginal delivery, clinical procedures or laboratory analysis. The study authors report in their paper that “the existence of live and replicating microbial populations in healthy fetal tissues is not compatible with fundamental concepts of immunology, clinical microbiology and the derivation of germ-free mammals.” The study authors consider their findings to be important to scientists’ understanding of human immune development. According to the ‘SciTechDaily’ news item, they “encourage researchers to focus their studies on the microbiomes of mothers and their newborn infants and on the microbial metabolites crossing the placenta which prepare the fetus for post-natal life in a microbial world.” Prof. Walter observes in the news item: “This consensus provides guidance for the field to move forward, to concentrate research efforts where they will be most effective. Knowing that the fetus is in a sterile environment, confirms that colonization by bacteria happens during birth and in early post-natal life, which is where therapeutic research on modulation of the microbiome should be focused.” The researchers’ conclusions also illustrate common pitfalls when conducting microbial analyses of other low-biomass environments. In their paper, the international experts therefore also advise scientists on how to prevent contamination when analysing samples expected to have no or low levels of bacteria, such as internal organs and tissues in the human body. The authors conclude: “The pursuit of a fetal microbiome serves as a cautionary example of the challenges of sequence-based microbiome studies when biomass is low or absent, and emphasizes the need for a trans-disciplinary approach that goes beyond contamination controls by also incorporating biological, ecological and mechanistic concepts.” For more information, please see: Homo.symbiosus project EarlyLife project Lacto-Be project BEHAVIOME project MetaPG project microTOUCH project ONCOBIOME project website MASTER project website IHMCSA project
Keywords
Homo.symbiosus, EarlyLife, Lacto-Be, BEHAVIOME, MetaPG, microTOUCH, ONCOBIOME, MASTER, IHMCSA, foetus, foetal, microbiome, bacteria, baby, womb
