A systematic review of the factors influencing microbial colonization of the preterm infant gut

Prematurity coupled with the necessary clinical management of preterm (PT) infants introduces multiple factors that can interfere with microbial colonization. This study aimed to review the perinatal, physiological, pharmacological, dietary, and environmental factors associated with gut microbiota of PT infants. A total of 587 articles were retrieved from a search of multiple databases. Sixty studies were included in the review after removing duplicates and articles that did not meet the inclusion criteria. Review of this literature revealed that evidence converged on the effect of postnatal age, mode of delivery, use of antibiotics, and consumption of human milk in the composition of gut microbiota of PT infants. Less evidence was found for associations with race, sex, use of different fortifiers, macronutrients, and other medications. Future studies with rich metadata are needed to further explore the impact of the PT exposome on the development of the microbiota in this high-risk population.

A Systematic Review of Dietary Influences on Fecal Microbiota Composition and Function among Healthy Humans 1-20 Years of Age

Diet is a key modulator of fecal microbiota composition and function. However, the influence of diet on the microbiota from toddlerhood to adolescence and young adulthood is less well studied than for infancy and adulthood. We aimed to complete a qualitative systematic review of the impacts of diet on the fecal microbiota of healthy humans 1-20 y of age. English-language articles, published after 2008, indexed in the PubMed/MEDLINE, Cochrane, Web of Science, and Scopus databases were searched using keywords and Medical Subject Headings terms. Quality assessment of included studies was conducted using the Quality Criteria Checklist derived from the Nutrition Evidence Library of the Academy of Nutrition and Dietetics. A total of 973 articles were identified through database searching and 3 additional articles were included via cross-reference. Subsequent to de-duplication, 723 articles were screened by title and abstract, of which 709 were excluded based on inclusion criteria established a priori. The remaining 14 studies were independently screened by 2 reviewers for final inclusion. Included studies were published between 2010 and 2019 and included 8 comparative cross-sectional studies, 4 cross-sectional studies, 1 randomized crossover study, and 1 substudy of a randomized 2-period crossover trial. Associations of a diet rich in indigestible plant polysaccharides with Prevotella, or with an enterotype dominated by this genus, often comprised of the species Prevotella copri, were observed. In addition, associations of a high-fat and -sugar diet with Bacteroides, or with an enterotype dominated by this genus, were observed predominantly in comparative cross-sectional and cross-sectional studies spanning the ages of 1-15 y. This review identified a gap in the literature for ages 16-20 y. In addition, randomized controlled trials for dietary intervention are needed to move from association-based observations to causal relations between diet and microbiota composition and function. This systematic review was registered at www.crd.york.ac.uk/prospero as CRD42020129824.