, while the skin microbiome of the mothers of the children whose microbiome was analyzed remained relatively constant over the same time period.
The findings come from what is believed to be the longest longitudinal study specific to the skin microbiome of infants and mothers.
“Even at 10 years, the skin microbiome does not look like an adult skin microbiome, based on composition of the ecosystem,” lead author, said in an interview during the virtual annual meeting of the American Academy of Dermatology. “The diversity of the microbiome in children’s skin is distinct to that of an adult’s skin. We all have the same bacteria present, but in children it is distributed differently because the bacteria set themselves up based on the nutrients and topography that they find on the skin. Since infant skin is unique to infants, so too is their microbiome when we compare it to adults. It’s been fascinating to observe these children grow and mature, and follow the skin microbiome along this same period.”
During five time points over a period of 10 years, Dr. Capone and her colleagues at the Skillman, N.J.–based Johnson & Johnson Consumer Experience Center, a research and development site, used 16s rRNA gene sequencing to evaluate the skin microbiome on the forearms and foreheads of 30 mothers and their 31 children. The study participants had Fitzpatrick skin types I-IV and the mean age of mothers was 37 years. “We used 16s rRNA gene sequencing for microbiome analysis at the beginning, as that was what was available 10 years ago,” said Dr. Capone, head of the microbiome platform for Johnson & Johnson Consumer Health. “Since then, we continue to use 16s for continuity, but also collected additional swabs for deeper analysis later.”
She and her colleagues often draw samples from the forearm in baby skin clinical studies, “as the arm is a good site to collect relevant data on the body overall,” she explained. “We chose the forearm and forehead specifically here so we can make same body site comparisons to adult sample data which we took from the mothers on the same areas of their body.” Time point 1 was 3 months to 1 year, time point 2 was 2-3 years, time point 3 was 5-6 years, time point 4 was 7-8 years, and time point 5 was 9-10 years.
The researchers found that the skin of infants during the first few weeks of life was similar at age 3 and 4 years. “From that second time point on, we see significant increases in richness and diversity, richness being presence or absence of various bacterial species, and diversity being the relative abundance of those species,” Dr. Capone said. “What you’re basically seeing is that there are new organisms, i.e., richness, coming into the microbiome. We start to detect new ones. Over time, the ecosystem is expanding. It’s evolving because it’s not yet set up.” The evolving skin microbiome on children was dominated by Streptococcus and Staphylococcus. In addition, children had higher levels of Streptococcus, Moraxella, Granulicatella, Gemella and Veillonella, compared with their adult mothers. Adult skin was colonized predominantly by Propionibacterium/Cutibacterium and Staphylococcus.
“The skin microbiome also increased in diversity over time on the forearm, but not face, of the mothers,” Dr. Capone said. “Previous studies have shown how stable the adult skin microbiome is, so it’s intriguing to see the changes that we saw on the mothers in this study.”
The increase in skin microbiome diversity observed in the children is likely due to a variety of factors, she continued, including inherent growth and development, dietary changes, as well as exposure to various environments and other people. “The fact remains that diversity is increasing over time, as the ecosystem evolves,” she said. “Eventually, the skin microbiome will become ‘adultlike’ in puberty, when lipid production increases. This drives increases in Cutibacterium acnes, particularly on the face.”
She acknowledged certain limitations of the study, including its relatively small size and the fact that some of the original subjects did not return for microbiome analysis at later time points. “We need larger cohort studies, additional deeper sequence data, metabolomics and transcriptomics to better understand the function of the skin microbiome over these various ages,” she said.
The study was sponsored by Johnson & Johnson Consumer. Dr. Capone and her two coauthors are employees of the company.