Composition of gut microbiota in infants in China and global comparison.

Symbiotic gut microbiota is essential for human health, and its compositional changes have been associated with various complex disorders. However, systematic investigation of the acquisition and development of gut microbial communities during early infancy are relatively rare, particularly for infants from non-Western countries. In this study, we characterize the colonization and development of infant microbiota in healthy Chinese infants and compare the pattern with those from other countries. The fecal microbiota of 2-month-old infants was considerably more diverse than that of neonates, as indicated by higher relative abundances of Veillonella, Clostridium, Bacteroides, Lactobacillus, Collinsella and Prevotella, and reduction of Escherichia and Enterococcus. The fecal microbiota of vaginally delivered infants (both neonates and 2-month-old) had significant enrichment of Bacteroides, Parabacteroides and Megamonas, whereas cesarean delivered infants had enrichment of Prevotella, Streptococcus and Trabulsiella. By global comparison, we identify three different enterotypes, referred as "P-type", "A-type "and "F-type" which were highly abundant in Proteobacteria, Actinobacteria and Firmicutes, respectively. The three enterotypes' compositons vary geographically. All Chinese infants in our study belong to the P-type. These findings may provide novel insights into our understanding of the establishment of infant fecal bacterial communities.

Effect of short-term room temperature storage on the microbial community in infant fecal samples.

Sample storage conditions are important for unbiased analysis of microbial communities in metagenomic studies. Specifically, for infant gut microbiota studies, stool specimens are often exposed to room temperature (RT) conditions prior to analysis. This could lead to variations in structural and quantitative assessment of bacterial communities. To estimate such effects of RT storage, we collected feces from 29 healthy infants (0-3 months) and partitioned each sample into 5 portions to be stored for different lengths of time at RT before freezing at -80 °C. Alpha diversity did not differ between samples with storage time from 0 to 2 hours. The UniFrac distances and microbial composition analysis showed significant differences by testing among individuals, but not by testing between different time points at RT. Changes in the relative abundance of some specific (less common, minor) taxa were still found during storage at room temperature. Our results support previous studies in children and adults, and provided useful information for accurate characterization of infant gut microbiomes. In particular, our study furnished a solid foundation and justification for using fecal samples exposed to RT for less than 2 hours for comparative analyses between various medical conditions.