The day to day activities brings humans in close contact with the surrounding environment. The contrast in these practices produces an impact on human physiology, development, and health. Evidences prove that the microbiome act as an interface that mediates interactions between the human body and the environment. Especially, the skin microbiome acts as the primary interface with the external environment and contributes to the host immune function as the first line of defense against pathogens. 

Besides knowing the important links between them, we still lack the proper knowledge about the primary establishment of the skin microbiome or the environmental factors contributing to its development. 

Thus a study compared the skin bacterial communities of infants, in four populations in Mexico and the United States that span the socioeconomic gradient, which were utilized for the prediction of the variation in physical and social environments in shaping the infant skin microbiome. 

The observations of the study were as follows-

• 16S rRNA bacterial gene sequencing was done on 119 samples (armpit, hand, and forehead).
• Sequencing revealed the infant skin bacterial diversity and composition to be influenced and curated by population-level factors, including those related to socioeconomic status and household composition and differs according to the skin site and infant age.
• Differences in infant-environment interactions (e.g. other people) change across the populations, which influence the infant microbial exposures and finally the composition of infant skin bacterial communities. 

Thus it is clear that the variation in microbial exposures influenced by the local environment in infancy, shows aftermath in the establishment of the skin microbiome across body sites, with implications for developmental and health outcomes.

This study explains the infant skin microbiome in general and contributes to the sparse literature on the infant skin microbiome in a field setting. Most of the microbiome research addresses patterns at a national scale, while the present study addresses the influence of population-level factors, such as maternal socioeconomic status and contact with caregivers, on infant skin bacterial communities. This helps to understand the influence of the local variables in the infant skin microbiome, further warranting additional studies to combine biological sample collection with questionnaires to establish the relation between the specific behaviours and infant microbial exposures. 

Clinical implications of these studies include infant care and health, while it could also be utilized to investigate the development of microbial communities of different body sites over time, with applications to specific health outcomes associated with the skin microbiome (e.g., immune system development or atopic dermatitis).

Source: Manus MB, Kuthyar S, Perroni-Marañón AG, Núñez-de la Mora A, Amato KR. Infant Skin Bacterial Communities Vary by Skin Site and Infant Age across Populations in Mexico and the United States. mSystems. 2020 Nov 3;5(6):e00834-20. doi: 10.1128/mSystems.00834-20. PMID: 33144313; PMCID: PMC7646528.