Microbiota and Necrotizing Enterocolitis.

Necrotizing enterocolitis (NEC) is an acquired gastrointestinal inflammatory condition with significant mortality and morbidity in preterm very low birth weight infants. The interplay between toll-like receptors, bacterial endotoxins, developmentally regulated excessive proinflammatory responses of the immature innate immune system, hypoxia, ischemia, reperfusion, free radicals, and the presence of substrates and bacterial endotoxins is thought to play an important role in the pathogenesis of NEC. The association (cause?) of various microbes (bacteria, viruses, and fungi) with NEC has intrigued researchers for many years. Availability of newer molecular methods (e.g., 16S ribosomal RNA gene-specific primers/pyrosequencing of fecal DNA) is expected to improve our understanding of the role of gut microbiota in the pathogenesis of NEC. Recent studies employing such methods to assess fecal microbiota are reviewed. Current evidence suggests that dysbiosis of the gut microbiota precedes the development of NEC in preterm infants. Further research is required to understand the significance of changes in the gut microbiome over the early postnatal period including the relative abundance of Gammaproteobacteria and the paucity of strict anaerobic bacteria that precedes NEC in preterm infants. Assessing the reproducibility of previous findings in large prospective studies with standardized methodology (e.g. sample processing, PCR primer, and DNA extraction) is important.