The individual-specific and diverse nature of the preterm infant microbiota

Objective: To examine the composition of the evolving microbiota of preterm infants at weeks 2 and 4 of life. Settings: The paediatric intensive care unit of the Cork University Maternity Hospital. Methods: The microbial diversity of faecal samples from 10 preterm infants was determined using 16S rRNA amplicon pyrosequencing technology. Results: In total, 452 863 sequences were obtained from 20 faecal samples collected from 10 preterm infants, allowing a level of analysis not previously reported. The preterm infant microbiota samples were dominated by Proteobacteria (46%), followed by Firmicutes (45%), while the phyla Actinobacteria (2%) and Bacteroidetes (7%) were detected at much lower levels at week 2 of life. This colonisation pattern was similar at week 4 of life. At the family level, Enterobacteriaceae were detected at 50% and 58% at weeks 2 and 4, respectively. The preterm infants were characterised by a lack of detectable Bifidobacterium and Lactobacillus genera commonly associated with the infant gut. In addition to the dominance of the Proteobacteria, a high level of interindividual variation was observed, indeed the relative proportions of different phyla, families and genera in different infants ranged from <1% to >90%. Conclusions: The results indicate that in addition to an uncharacteristic microbiota relative to that reported for healthy term infants, there was a large interindividual variation in the faecal microbiota diversity of preterm infants suggesting that the preterm microbiota is individual-specific and does not display a uniformity among infants.