Composition of bifidobacterial population in irritable bowel syndrome and control subjects

Irritable bowel syndrome (IBS) is a chronic intestinal disorder that may involve an altered intestinal microbiota. Although in some studies lower numbers of bifidobacteria have been detected in IBS subjects compared to healthy controls, the composition of bifidobacterial population in IBS subjects is poorly known. The aim of the present study was to investigate the diversity and stability of faecal bifidobacterial population in IBS and control subjects. Faecal samples were obtained from 19 IBS and 16 control subjects at three sampling points (0, 3 and 6 months) and analysed by PCR-DGGE with Bifidobacterium-specific primers Bifl 64-f and Bif662-GC-r. In addition fresh samples from two sampling occasions were cultured on Beerens to determine the bifidobacterial counts. PCR-DGGE analysis revealed 1-7 fragments per sample. No difference in the bifidobacterial count or in the diversity or stability of bifidobacterial population in general was observed between IBS and control groups. However, a single fragment, identified by 16S rDNA sequencing tentatively as uncultured Bifidobacterium, was more commonly detected in IBS than in control subjects. The identity and role of this fragment in IBS warrants further studies.