Microbial Inheritance: Could Mother-to-Child Microbiome Transmission Be the Key to Managing Atopic Dermatitis?

It is a known fact that each and every individual has a unique microbiome, comprising a community of bacteria, fungi, viruses and protozoa (commonly referred to as microbes). Interestingly, the origin of a person's microbiome stems from the moment they were born. Studies show that regardless of birthing route (vaginal or caesarean), 58.5% of a baby’s microbiome is acquired from their mother (Bogaert., et al 2023). 

In recent years, the mother-to-child microbiome transfer has become a topic of note within the microbiome space. Despite growing literature about the baby microbiome, it is still an area that needs further exploration. This article will aim to highlight current research on the topic, whilst focusing on Atopic Dermatitis as seen within newborns and infants. It is crucial to understand and expand upon this research as it might lead to uncovering new microbial candidates that could impact skin conditions, such as Atopic Dermatitis, in early life and unlock their treatments. 

A Background on Atopic Dermatitis

There are numerous paediatric skin disorders that can affect an infant in early life. Typically, we find that Atopic Dermatitis (AD), is the most prevalent skin disorder amongst infants and is an important condition to consider (Gilaberte et al., 2020). It has been seen that infants that suffer from AD can go on to develop a highly contagious condition known as impetigo (a bacterial infection that typically affects infants and young children)( Mannschreck et al.,2020).  According to a study published in 2015 “the median impetigo prevalence in children was 12.3%, (IQR 4.2–19.3%)” (Bowen et al., 2015).  It is known that the skin microbiome of infants is completely different to that of adults, however we also know that the pathophysiology and the inflammatory cytokines that are triggered are alike. The pathogenesis of AD is incredibly complex, which is why pinpointing its treatment has been difficult. Most of the drugs that are currently under investigation or are showing some positive results in clinical trials targeting skin cells, but we now understand that there are more solutions that intend to target the microbiome component (Baldwin et al., 2020). 

At present, there are two ways of exploring AD. One way is to look directly at the source and extract samples of the skin microbiome to observe changes in its profile. The alternative is to look at the gut microbiome, pulling from previously published literature that suggests that there is a convincing link between the gut microbiome and skin health.

The Role of Staphylococcus aureus in AD.

AD sites on the body are known to be dominated by Staphylococcus aureus (S. aureus), which is the most studied and well-described bacteria linked to AD. It is known that S. aureus goes through a stage of growth which leads to AD flare-ups in individuals (Khadka et al., 2021). This means that by identifying the growth of S. aureus early a threshold can be determined that when surpassed could be used to predict when a flare-up could be triggered, which may give rise to the opportunity for prevention. 

Mother-to-child Microbiome Transfer

When exploring early colonisation of the baby microbiome, the transfer from mother-to-child is more commonly talked about. Until recently, it has been agreed that the womb is sterile. However, new research has been carried out on amniotic fluid which suggests that certain microbes might be present there as well (Kaisanlahti et al., 2023). Although the evidence used to support this research in scientific literature is generally regarded as weak, more studies are crucial before this can be proven or disputed. Another theory surrounding the amniotic fluid explores the idea that a baby might in fact ingest the amniotic fluid, resulting in bacterial transfer from the mother. This is another area that is currently lacking in evidence and requires further research.

There is a significant transfer of microbes from a mother to her child during vaginal delivery as well as through skin-to-skin contact in a baby’s early moments of life. During breastfeeding, the bacteria surrounding the nipple is also transferred orally. According to recent publications, 58.5% of a baby’s microbiome is a direct result of their mother. The rest is attributed to their environment and other external factors (Bogaert., et al 2023). 

Whether there is a link between birthing route (vaginal or caesarean) and AD is currently unclear, with mixed study results and a vast majority of scientists agreeing that a clear link cannot consistently be established.

Infant Early Life and AD: Skin Microbiome

There are several published papers which explore the association of the baby microbiome with AD. For the purposes of this article “The skin microbiome in the first year of life and its association with atopic dermatitis” will be evaluated more closely (Rapin., et al 2023). 

This study was conducted in Oslo, Norway, in which the skin of babies was sampled at four timepoints (At birth, 3 months, 6 months and 12 months). Various investigational factors, including the composition of the skin microbiome, birthing methods, environmental influences, parental factors, and breastfeeding, were analyzed to assess potential associations with skin immunities.

Thee results of this study ultimately showed that these factors were all correlated and instrumental in the development of the baby’s microbiome. The study further showed that each variable held a different influence on the skin microbiome depending on the timepoint the sample was taken at. For example, at birth the mode of delivery was most instrumental. However, as time went on different factors became more influential, such as birth location, breastfeeding, maternal AD, maternal food allergies, and exposure to pets. 

It is known that the delivery of a baby shapes the microbiome in early life. However, can an association be found between the birthing route and the development of AD? 

This Oslo study concluded that ultimately there is not a strong association between delivery mode and AD pathogenesis. The reasoning behind this conclusion was that the few differences that were noted at birth levelled out by 12 months and no longer held differentiable significance (Rapin., et al 2023). 

Infant early life and AD: Gut Microbiome

It is interesting to note that the conclusions drawn from the skin microbiome study in Oslo is mirrored by another study that was conducted on the gut microbiome in association with AD. The study in question “The associations of maternal and children’s gut microbiota with the development of atopic dermatitis for children ages 2 years” (Fan et al., 2022) compared the gut microbiome of mothers and babies, and found that mothers of infants and toddlers with AD had higher abundance of Candidatus_Stoquefichus and Pseudomonas in pregnancy. The study also found that infants and toddlers with AD had a higher abundance of Eubacterium_xylanophilum group at birth, Ruminococcus_gauvreauii group at 1 year of age, UCG-002 at 2 years, and lower abundance of Gemella and Veillonella at 2 years of age. It is particularly interesting that the study also demonstrated a lower abundance of Prevotella in mothers of infants and toddlers with AD compared to mothers of the control group. 

The Skin Microbiome: New Findings

A subsequent study performed shotgun metagenomic sequencing on the skin microbiome, it found that a dysbiosis in the microbiome exists prior to the onset of AD (Chaudhary et al., 2023). Firstly, the study affirmed that birth mode and demographics in fact did not associate with subsequent AD development. However, what the study did find was that by measuring the skin of babies, reduced Prevotella abundance could be a predictor of subsequent AD development. The benefits of using shotgun metagenomics meant that more functional analysis could be conducted, ultimately showing that there was a significant reduction in Prevotella abundance in the AD group compared to the control group. Additionally, there are some differences in host and bacterial features in certain genes that are interesting to target based on what is seen in shotgun metagenomic sequencing. When looking at lipid profiling they showed a complete difference between the AD group and control group. 

Prevotella has been found to be a good candidate as a potential predictor of AD development, as demonstrated by this study.

Conclusion

There is considerable research being conducted on the baby microbiome as well as AD in adults, however more research needs to be carried out in order to make stronger links between what might be the root cause of AD in babies and infants. The publications highlighted within the article give some good insights into AD and some of the positive and negative correlations between different variables. Notable, the role of Prevotella in AD might be an interesting one to explore further as there is strong evidence to suggest that it could be a good diagnostic target to better understand how AD might develop. At present, the majority of treatments within the personal care and pharmaceutical industry continue to target Staphylococcus aureus, with proven improvements and more clinical data to show that this approach is effective in adults with AD. However, new candidates must be studied so that the industry can adapt the way it approaches AD treatment and intervention in the future, particularly regarding the development of AD in children. 

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