Reduced gut bacterial diversity in early life predicts feeding intolerance in preterm neonates

Microbiota plays a crucial role in intestinal maturation in preterm newborns. The clinical manifestation of the immaturity of the gastro-intestinal tract is called feeding intolerance (FI). This condition may resolve spontaneously or dramatically evolve into necrotizing enterocolitis. One of the most challenging tasks for the neonatologist is to identify those neonates that will develop the disease early in order to adequately provide nutrition to these patients, from the very first hours of life. A close interplay between the maturity of the gastro-intestinal tract and gut microbiota has been described; however, in preterm neonates, this relationship is still undefined. We analyzed the bacterial composition of stool samples, collected early in life, from 30 preterm newborns classified as intolerant or tolerant according to the degree of readiness of the gastro-intestinal tract to receive enteral nutrition. The Pielou evenness index was significantly increased in intolerant compared with tolerant newborns. Data corrected for confounding variables confirmed that the occurrence of gut maturation was independently influenced by Pielou evenness at birth. A lower bacterial diversity very early in life is associated with improved feeding tolerance in preterm newborns. The abundance analysis showed that neonates not ready to receive enteral nutrition for feeding intolerance show, after birth, an increased abundance of Proteobacteria, Lachnospiracae, Enterobacter and Acinetobacter. We can argue that those are the taxa that prevent the establishment of pioneer bacteria. A lower alpha-diversity, in the first days of life, may facilitate the seeding of beneficial pioneer bacteria that, in turn, drive healthy microbial colonization during neonatal life.