Is the abundance of Faecalibacterium prausnitzii relevant to Crohn's disease?

Abstract

Reports that bacteria within the Firmicutes phylum, especially the species Faecalibacterium prausnitzii, are less abundant in Crohn's disease (CD) patients and supernatants from cultures of this bacterium are anti-inflammatory prompted the investigation of the possible correlations between the abundance of F. prausnitzii and the response to treatment in patients with gut diseases and healthy controls. In a randomized, double-blind trial, faeces were collected from healthy volunteers, and from patients with active CD, ulcerative colitis (UC) and irritable bowel syndrome before and after treatment. The levels of F. prausnitzii DNA in faecal suspensions were determined by PCR. Treatment by an elemental diet was effective, resulting in decreases in both the Harvey and Bradshaw index (P<0.001) and the concentrations of serum C-reactive protein (P<0.05). The total levels of F. prausnitzii in faecal samples from CD patients at presentation were lower than those in the other groups both before and after the treatment. There was no correlation between F. prausnitzii abundance and the severity of CD before treatment. Clinical improvement unexpectedly correlated with a significant decrease in the abundance of F. prausnitzii, especially the A2-165 subgroup (P<0.05). Our data suggest that a paucity of F. prausnitzii in the gastrointestinal microbial communities is likely to be a minor aetiological factor in CD: recovery following elemental diet is attributed to lower levels of gut flora.

Fig. 1

Relative quantity of Faecalibacterium prausnitzii in faecal DNA determined by PCR. Agarose gel showing bands of the F. prausnitzii amplicon from 22 faecal samples. The upper band of 778 bp corresponds to the M21/2 subgroup; the lower 650 bp band corresponds to the A2-165 subgroup. The same amount of template DNA was added to each PCR reaction, and so these differences indicate the relative amount of F. prausnitzii in each patient. Where a PCR product was present, the brightness of the band was measured using the software quantity one (Bio-Rad) and converted to DNA amount by reference to a 1 kb ladder (New England Biolabs: right-hand lane).