7, 8, 9, 10, 11 Prematurity, lack of diversity in the gut bacterial communities, and the presence of pathogenic bacteria have also been associated with systemic inflammation and the development of sepsis, as well as necrotizing enterocolitis, all of which are important complications of prematurity. 1, 2, 3, 4, 5, 6 In premature infants it has been hypothesized that antibiotic use, coupled with the infants’ underdeveloped immune systems and gut epithelia, promotes intestinal bacterial communities that are less diverse and enriched with potential pathogens. This allows for translocation of bacteria from the gut to the bloodstream, leading to systemic inflammation or sepsis.

Premature infants have an immature gastrointestinal tract, with a gut epithelium that has diminished barrier function and increased permeability. Gestational age at birth and early antibiotic exposure have significant effects on the premature infant gut microbiota. Newborn antibiotic use among premature infants was associated with lower Bifidobacterium and Bacteroides abundance ( p = 0.015 and p = 0.041). Alpha-diversity varied between extremely premature (<28 weeks gestation) and very premature infants (≥28 but <32 weeks, p = 0.011), as well as between extremely and moderate-to-late premature infants (≥32 and <37 weeks, p = 0.004). Gut bacterial alpha-diversity differed between premature and term infants at 6 weeks of age, after adjusting for exposures ( p = 0.027). Gut colonization patterns were determined with 16S rDNA microbiome profiling. To determine the effect of gestational age at birth and postnatal exposures on gut bacterial colonization in infants, we analyzed 65 stool samples from 17 premature infants in the neonatal intensive care unit, as well as 13 samples from 13 mostly moderate-to-late premature infants and 189 samples from 176 term infants in the New Hampshire Birth Cohort Study. The impact of degree of prematurity at birth on premature infant gut microbiota has not been extensively studied in comparison to term infants in large cohorts.

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