Higher prevalence and abundance of Bdellovibrio bacteriovorus in the human gut of healthy subjects

Abstract

Introduction: Members of the human intestinal microbiota are key players in maintaining human health. Alterations in the composition of gut microbial community (dysbiosis) have been linked with important human diseases. Understanding the underlying processes that control community structure, including the bacterial interactions within the microbiota itself, is essential. Bdellovibrio bacteriovorus is a gram-negative bacterium that preys other gram-negative species for survival, acting as a population-balancer. It was found in terrestrial/aquatic ecosystems, and in animal intestines, postulating its presence also in the human gut.

Methods: The present study was aimed to evaluate, by end-point PCR and qPCR, the presence of B. bacteriovorus in intestinal and faecal biopsy specimens from 92 paediatric healthy subjects and patients, suffering from Inflammatory Bowel Diseases (IBD), Celiac disease and Cystic fibrosis (CF).

Results: i) B. bacteriovorus was present and abundant only in healthy individuals, while it was heavily reduced in patients, as in the case of IBD and Celiac, while in CF patients and relative controls we observed comparable results; ii) B. bacteriovorus seemed to be mucosa-associated, because all IBD and Celiac biopsies (and related controls) were treated with mucus-removing agents, leaving only the mucosa-attached microflora; iii) B. bacteriovorus abundance was district-dependent, with a major preponderance in duodenum, and gradually decreasing up to rectum; iv) B. bacteriovorus levels significantly dropped in disease status, in duodenum and ileum.

Conclusions: Results obtained in this study could represent the first step for new therapeutic strategies aimed to restore a balance in the intestinal ecosystem, utilizing Bdellovibrio as a probiotic.

Figure 1. Prevalence of B. bacteriovorus in subjects from IBD, Celiac, and CF groups.

Ninety-two subjects were enrolled: 23 within ‘IBD group’ (9 CD, 6 UC, 8 controls), 18 within ‘Celiac group’ (10 Celiac, 8 controls), and 51 within ‘CF group’ (35 CF, 16 controls). Bars represent the relative prevalence of B. bacteriovorus among subjects. P values were computed through χ² test.

Figure 2. Relative abundance of B. bacteriovorus in samples from IBD and Celiac groups.

In total, 138 samples were taken into account: 69 intestinal biopsies from ‘IBD group’ (27 CD, 18 UC, 24 controls), 18 within ‘Celiac group’ (10 Celiac, 8 controls), and 51 faecal samples within ‘CF group’ (35 CF, 16 controls). Differences in relative abundances were assessed by Mann-Whitney U test.

Figure 3. Longitudinal distribution of B. bacteriovorus along the intestine.

We took into account samples from controls (grey bars) and diseased (black bars) subjects within each group. Bars represent the mean relative abundance of B. bacteriovorus found in these samples, divided by intestinal districts. P values were assessed by Mann-Whitney U test.