Temporal dynamics of the very premature infant gut dominant microbiota.

Background: The very-preterm infant gut microbiota is increasingly explored due to its probable role in the development of life threatening diseases. Results of high-throughput studies validate and renew the interest in approaches with lower resolution such as PCR-Temporal Temperature Gel Electrophoresis (TTGE) for the follow-up of dominant microbiota dynamics. We report here an extensive longitudinal study of gut colonization in very preterm infants. We explored by 16S rDNA-based PCR-TTGE a total of 354 stool specimens sampled during routine monitoring from the 1(st) to the 8(th) week of life in 30 very pre-term infants born before 30 weeks of gestational age.

Results: Combining comparison with a diversity ladder and sequencing allowed affiliation of 50 Species-Level Operational Taxonomic Units (SLOTUs) as well as semi-quantitative estimation of Operational Taxonomic Units (OTUs). Coagulase-negative staphylococci, mainly the Staphylococcus epidermidis, was found in all the infants during the study period and was the most represented (75.7% of the SLOTUs) from the first days of life. Enterococci, present in 60% of the infants were early, highly represented and persistent colonizers of the premature gut. Later Enterobacteriaceae and the genus Clostridium appeared and were found in 10 (33%) and 21 infants (70%), respectively. We showed a high representation of Veillonella in more than a quarter of the infants and being able to persistently colonize premature gut. The genera Anaerococcus, Aquabacterium, Bacillus, Bifidobacterium, Corynebacterium, Micrococcus, Oceanobacillus, Propionibacterium, Pseudomonas, Rothia, Sarcina, Sneathia and Streptococcus were observed as transient or persistent colonizers, each genus being found in a minority of infants.

Conclusions: Despite low resolution, PCR-TTGE remains complementary to high-throughput sequencing-based approaches because it allows the follow-up of dominant bacteria in gut microbiota in a large longitudinal cohorts of preterm neonates. We described the development of pre-term gut microbiota that should be now replaced regarding the functional role of major OTUs.