Microbial community analysis reveals high level phylogenetic alterations in the overall gastrointestinal microbiota of diarrhoea-predominant irritable bowel syndrome sufferers.
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.
Krogius-Kurikka
Lotta
L
Department of Basic Veterinary Sciences, Faculty of Veterinary Medicine, PO Box 66, FI-00014 University of Helsinki, Helsinki, Finland. lotta.krogius@helsinki.fi
Lyra
Anna
A
Malinen
Erja
E
Aarnikunnas
Johannes
J
Tuimala
Jarno
J
Paulin
Lars
L
Mäkivuokko
Harri
H
Kajander
Kajsa
K
Palva
Airi
A
D039903:Actinobacteria / Q000235:genetics; D000328:Adult; D041963:Bacteroidetes / Q000235:genetics; D016022:Case-Control Studies; D004269:DNA, Bacterial / Q000032:analysis / Q000235:genetics; D003967:Diarrhea / Q000209:etiology / Q000382:microbiology*; D005243:Feces / Q000737:chemistry / Q000382:microbiology*; D005260:Female; D041981:Gastrointestinal Tract / Q000382:microbiology*; D006094:Gram-Positive Bacteria / Q000235:genetics; D006801:Humans; D043183:Irritable Bowel Syndrome / Q000150:complications / Q000382:microbiology*; D008297:Male; D008875:Middle Aged; D010802:Phylogeny; D020560:Proteobacteria / Q000235:genetics; D012329:RNA, Bacterial / Q000032:analysis / Q000235:genetics
D004269:DNA, Bacterial; D012329:RNA, Bacterial