The human microbiome and its potential importance to pediatrics

Abstract

The human body is home to more than 1 trillion microbes, with the gastrointestinal tract alone harboring a diverse array of commensal microbes that are believed to contribute to host nutrition, developmental regulation of intestinal angiogenesis, protection from pathogens, and development of the immune response. Recent advances in genome sequencing technologies and metagenomic analysis are providing a broader understanding of these resident microbes and highlighting differences between healthy and disease states. The aim of this review is to provide a detailed summary of current pediatric microbiome studies in the literature, in addition to highlighting recent findings and advancements in studies of the adult microbiome. This review also seeks to elucidate the development of, and factors that could lead to changes in, the composition and function of the human microbiome.

FIGURE 1

16S bacterial rRNA analysis reveals influence of delivery mode on the neonatal microbiome. UniFrac analysis revealed similarities and clustering of bacterial communities based on the mother’s body habitat or the delivery mode of the newborn. Each colored point represents a similar community in specific body sites of the mother and all newborn body habitats. The percentage of variation of the principal coordinates analysis is indicated in white text on both axes. (Reproduced with permission from Dominguez-Bello MG, Costello EK, Contreras M, et al. Delivery mode shapes the acquisition and structure of the initial microbiota across multiple body habitats in newborns. Proc Natl Acad Sci USA. 2010;107[26]:11973.)

FIGURE 2

Effects of diet, host, and environmental factors on the microbiome. Antibiotic use, diet, host, and environmental factors can affect the composition of the microbiota. In this model, balanced microbial composition may result in symbiosis among resident microbes, production of immunomodulatory compounds, and subsequent regulation of the immune response. Disruption or alteration of the microbiota by environmental factors such as diet and antibiotic use could result in dysbiosis and dysregulation of the immune response. (Reproduced with permission from Maslowski KM, Mackay CR. Diet, gut microbiota and immune responses. Nat Immunol. 2011;12[1]:6.)

FIGURE 3

Disease states reveal phylum-level differences compared with healthy controls. Comparisons of the relative abundances of predominant bacterial phyla in IBD, type 2 diabetes, and NEC compared with healthy controls. Fecal samples from infants with NEC and patients with type 2 diabetes were compared with healthy controls revealing a predominance of Proteobacteria in patients with NEC. Cecal samples from patients with IBD were compared with healthy controls, and relative abundances were assessed. (Reproduced with permission from Spor A, Koren O, Ley R. Unravelling the effects of the environment and host genotype on the gut microbiome. Nat Rev Microbiol. 2011;9[4]:281.)