title: An irritable bowel syndrome subtype defined by species-specific alterations in faecal microbiota.
abstract: OBJECTIVE
  Irritable bowel syndrome (IBS) is a common functional gastrointestinal disorder that may be triggered by enteric pathogens and has also been linked to alterations in the microbiota and the host immune response. The authors performed a detailed analysis of the faecal microbiota in IBS and control subjects and correlated the findings with key clinical and physiological parameters.
  
  
  METHODS
  The authors used pyrosequencing to determine faecal microbiota composition in 37 IBS patients (mean age 37 years; 26 female subjects; 15 diarrhoea-predominant IBS, 10 constipation-predominant IBS and 12 alternating-type IBS) and 20 age- and gender-matched controls. Gastrointestinal and psychological symptom severity and quality of life were evaluated with validated questionnaires and colonic transit time and rectal sensitivity were measured.
  
  
  RESULTS
  Associations detected between microbiota composition and clinical or physiological phenotypes included microbial signatures associated with colonic transit and levels of clinically significant depression in the disease. Clustering by microbiota composition revealed subgroups of IBS patients, one of which (n=15) showed normal-like microbiota composition compared with healthy controls. The other IBS samples (n=22) were defined by large microbiota-wide changes characterised by an increase of Firmicutes-associated taxa and a depletion of Bacteroidetes-related taxa.
  
  
  CONCLUSIONS
  Detailed microbiota analysis of a well-characterised cohort of IBS patients identified several clear associations with clinical data and a distinct subset of IBS patients with alterations in their microbiota that did not correspond to IBS subtypes, as defined by the Rome II criteria.
authors.affiliation: Department of Microbiology, University College Cork, Cork, Ireland.
authors.forename: Ian B
authors.initials: IB
authors.lastname: Jeffery
authors.forename: Paul W
authors.initials: PW
authors.lastname: O'Toole
authors.forename: Lena
authors.initials: L
authors.lastname: Öhman
authors.forename: Marcus J
authors.initials: MJ
authors.lastname: Claesson
authors.forename: Jennifer
authors.initials: J
authors.lastname: Deane
authors.forename: Eamonn M M
authors.initials: EM
authors.lastname: Quigley
authors.forename: Magnus
authors.initials: M
authors.lastname: Simrén
mesh_terms: D000328:Adult; D041963:Bacteroidetes / Q000235:genetics / Q000302:isolation & purification*; D016022:Case-Control Studies; D003013:Clostridium / Q000235:genetics / Q000302:isolation & purification; D005243:Feces / Q000382:microbiology*; D005260:Female; D020459:Genes, rRNA; D006094:Gram-Positive Bacteria / Q000235:genetics / Q000302:isolation & purification*; D006801:Humans; D043183:Irritable Bowel Syndrome / Q000175:diagnosis / Q000382:microbiology*; D008297:Male; D054892:Metagenome / Q000235:genetics; D011788:Quality of Life; D011795:Surveys and Questionnaires