MD/PhD Student Medical University of South Carolina College of Medicine Charleston, South Carolina, United States
Background: After birth, the term neonatal gut becomes colonized by commensal bacteria that benefit host health. Premature infants, however, are prone to abnormal colonization that increases the risk for neonatal intestinal disease such as necrotizing enterocolitis (NEC). Breastfeeding confers a lower risk for NEC, and this is likely due to prebiotics, probiotics, and anti-inflammatory cytokines present in breast milk. Despite the known associations of NEC with gut microbiota and breastfeeding, the exact interactions between preterm gut microbes and various milk types remains relatively unexplored. Furthermore, Lactobacillus are frequently included in probiotic supplements, but the interplay between Lactobacillus, milk, and NEC is not fully understood. Objective: We hypothesize that in in vitro models of preterm microbiota, human breast milk exerts an overall beneficial modulatory effect on bacterial composition. We also suspect that the anti-inflammatory properties of Lactobacillus are enhanced when treated with fresh breast milk compared to formula. Design/Methods: Stool samples from preterm infants were incubated anaerobically in mini-bioreactors overnight at 37°C to establish complex communities. The next day, they were supplemented with fresh milk with or without fortifier, donor milk with or without fortifier, formula, vitamin mix, iron mix, or water and incubated for another 24 hrs. Bacterial gDNA was examined by qPCR and back-calculated to CFU to quantify bacterial composition. To examine the effect of milk on Lactobacillus metabolites, we grew six Lactobacillus (L. acidophilus, L. breve, L. johnsonii, L. paracasei, L. reuteri, and L. rhamnosus) in a defined medium supplemented with fresh milk, formula, or water. After overnight incubation, supernatants were collected for nontargeted metabolomics. The supernatant was also applied to preterm intestinal organoids to examine epithelial responses.
