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Open Access Research article

Microbial community analysis reveals high level phylogenetic alterations in the overall gastrointestinal microbiota of diarrhoea-predominant irritable bowel syndrome sufferers

Lotta Krogius-Kurikka1, Anna Lyra1, Erja Malinen1, Johannes Aarnikunnas1, Jarno Tuimala27, Lars Paulin3, Harri Mäkivuokko47, Kajsa Kajander56 and Airi Palva1*

Author Affiliations

1 Department of Basic Veterinary Sciences, Faculty of Veterinary Medicine, PO Box 66, FI-00014 University of Helsinki, Helsinki, Finland

2 CSC - Scientific Computing Ltd, Espoo, Finland

3 DNA Sequencing Laboratory, Institute of Biotechnology, University of Helsinki, Helsinki, Finland

4 Danisco Innovation, Kantvik, Finland

5 Valio Ltd, Research Centre, Helsinki, Finland

6 Department of Biomedicine, Faculty of Medicine, University of Helsinki, Helsinki, Finland

7 The Finnish Red Cross, Blood Service, Helsinki, Finland

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BMC Gastroenterology 2009, 9:95  doi:10.1186/1471-230X-9-95

Published: 17 December 2009

Abstract

Background

A growing amount of scientific evidence suggests that microbes are involved in the aetiology of irritable bowel syndrome (IBS), and the gastrointestinal (GI) microbiota of individuals suffering from diarrhoea-predominant IBS (IBS-D) is distinguishable from other IBS-subtypes. In our study, the GI microbiota of IBS-D patients was evaluated and compared with healthy controls (HC) by using a high-resolution sequencing method. The method allowed microbial community analysis on all levels of microbial genomic guanine plus cytosine (G+C) content, including high G+C bacteria.

Methods

The collective faecal microbiota composition of ten IBS-D patients was analysed by examining sequences obtained using percent G+C (%G+C) -based profiling and fractioning combined with 16S rRNA gene clone library sequencing of 3267 clones. The IBS-D library was compared with an analogous healthy-control library of 23 subjects. Real-time PCR analysis was used to identify phylotypes belonging to the class Gammaproteobacteria and the order Coriobacteriales.

Results

Significant differences were found between clone libraries of IBS-D patients and controls. The microbial communities of IBS-D patients were enriched in Proteobacteria and Firmicutes, but reduced in the number of Actinobacteria and Bacteroidetes compared to control. In particular, 16S rDNA sequences belonging to the family Lachnospiraceae within the phylum Firmicutes were in greater abundance in the IBS-D clone library.

Conclusions

In the microbiota of IBS-D sufferers, notable differences were detected among the prominent bacterial phyla (Firmicutes, Actinobacteria, Bacteroidetes, and Proteobacteria) localized within the GI tract.