The intestinal flora of the preterm infant and how it relates to NEC.
The normal pattern of colonization of the intestine is disturbed by: prematurity; by caesarian delivery; by antibiotics; and by feeding formula rather than breast milk. The abnormal colonization of the intestine of the preterm may well be related to the pathogenesis of Necrotizing Enterocolitis. A previous study showed that preterm infants have a reduced variety of organisms in their bowel, and those who develop NEC seem to have an even more disturbed colonization, with a reduction in variety before the symptoms appear (Wang Y, Hoenig JD, Malin KJ, Qamar S, Petrof EO, Sun J, et al. 16S rRNA gene-based analysis of fecal microbiota from preterm infants with and without necrotizing enterocolitis. ISME J. 2009;3(8):944-54. http://www.nature.com/ismej/journal/v3/n8/full/ismej200937a.html)
A new study by Dr Joseph Neu’s group in Florida didn’t find reduced diversity but instead found that babies who develop NEC seem to have a different profile of colonizing organisms, and they may have identified a specific new pathogen which seems to become prominent in the 72 hours before the diagnosis of NEC.
Mai V, Young CM, Ukhanova M, Wang X, Sun Y, Casella G, et al. Fecal Microbiota in Premature Infants Prior to Necrotizing Enterocolitis. PLoS One. 2011;6(6):e20647. http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0020647
In this study weekly stool samples were collected and analyzed with high throughput molecular techniques which can identify many thousands of strains. Some of the babies developed NEC, and the samples one week before and within 72 hours before the diagnosis were compared with controls, who did not get NEC.
One of the bacterial signatures detected more frequently in NEC cases (p<0.01) matched closest to γ-Proteobacteria. Although this sequence grouped to the well-studied Enterobacteriaceae family, it did not match any sequence in Genbank by more than 97%. Our observations suggest that abnormal patterns of microbiota and potentially a novel pathogen contribute to the etiology of NEC.
A very elegant series of studies in preterm pigs, (summarized in Siggers RH, Siggers J, Thymann T, Boye M, Sangild PT. Nutritional modulation of the gut microbiota and immune system in preterm neonates susceptible to necrotizing enterocolitis. The Journal of Nutritional Biochemistry. 2011;22(6):511-21. http://www.sciencedirect.com/science/article/pii/S0016508506003374 ) supports the role of Colostrum, abnormal gut colonization and enhanced immune responses in the preterm as factors in the development of NEC, and the role of probiotics in prevention.