OBJECTIVES:

Human intestinal microbiota has a number of important roles in human health and is also implicated in several gastrointestinal disorders. The goal of this study was to determine the gut microbiota in two groups of pre-and adolescent children: healthy volunteers and children diagnosed with diarrhea-predominant irritable bowel syndrome (IBS-D).

METHODS:

Phylogenetic Microbiota Array was used to obtain quantitative measurements of bacterial presence and abundance in subjects’ fecal samples. We utilized high-throughput DNA sequencing, quantitative PCR, and fluorescentin situhybridization to confirm microarray findings.

RESULTS:

Both sample groups were dominated by the phyla Firmicutes, Bacteroidetes, and Actinobacteria, which cumulatively constituted 91% of overall sample composition on average. A core microbiome shared among analyzed samples encompassed 55 bacterial phylotypes dominated by genusRuminococcus; members of generaClostridium, Faecalibacterium, Roseburia, Streptococcus, andBacteroideswere also present. Several genera were found to be differentially abundant in the gut of healthy and IBS groups: levels ofVeillonella, Prevotella, Lactobacillus, andParasporobacteriumwere increased in children diagnosed with IBS, whereas members ofBifidobacteriumandVerrucomicrobiumwere less abundant in those individuals. By calculating a nonparametric correlation matrix among abundances of different genera in all samples, we also examined potential associations among intestinal microbes. Strong positive correlations were found between abundances ofVeillonellaand bothHaemophilusandStreptococcus, betweenAnaerovoraxandVerrucomicrobium, and betweenTannerellaandAnaerophaga.

CONCLUSIONS:

Although at the higher taxonomical level gut microbiota was similar between healthy and IBS-D children, specific differences in the abundances of several bacterial genera were revealed. Core microbiome in children was dominated by Clostridia. Putative relationships identified among microbial genera provide testable hypotheses of cross-species associations among members of human gut microbiota.