title: Irritable Bowel Syndrome, Particularly the Constipation-Predominant Form, Involves an Increase inMethanobrevibacter smithii, Which Is Associated with Higher Methane Production.
abstract: OBJECTIVE
  BecauseMethanobrevibacter smithiiproduces methane, delaying gut transit, we evaluatedM. smithiiloads in irritable bowel syndrome (IBS) patients and healthy controls (HC).
  
  
  METHODS
  Quantitative real-time polymerase chain reaction forM. smithiiwas performed on the feces of 47 IBS patients (Rome III) and 30 HC. On the lactulose hydrogen breath test (LHBT, done for 25 IBS patients), a fasting methane result ≥10 ppm using 10 g of lactulose defined methane-producers.
  
  
  RESULTS
  Of 47, 20 had constipation (IBS-C), 20 had diarrhea (IBS-D) and seven were not sub-typed. TheM. smithiicopy number was higher among IBS patients than HC (Log₁₀5.4, interquartile range [IQR; 3.2 to 6.3] vs 1.9 [0.0 to 3.4], p<0.001), particularly among IBS-C compared to IBS-D patients (Log₁₀6.1 [5.5 to 6.6] vs 3.4 [0.6 to 5.7], p=0.001); the copy number negatively correlated with the stool frequency (R=-0.420, p=0.003). TheM. smithiicopy number was higher among methane-producers than nonproducers (Log₁₀6.4, IQR [5.7 to 7.4] vs 4.1 [1.8 to 5.8], p=0.001). Using a receiver operating characteristic curve, the best cutoff forM. smithiiamong methane producers was Log₁₀6.0 (sensitivity, 64%; specificity, 86%; area under curve [AUC], 0.896). The AUC for breath methane correlated with theM. smithiicopy number among methane producers (r=0.74, p=0.008). Abdominal bloating was more common among methane producers (n=9/11 [82%] vs 5/14 [36%], p=0.021).
  
  
  CONCLUSIONS
  Patients with IBS, particularly IBS-C, had higher copy numbers ofM. smithiithan HC. On LHBT, breath methane levels correlated withM. smithiiloads.
authors.affiliation: Department of Microbiology, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, India.
authors.forename: Ujjala
authors.initials: U
authors.lastname: Ghoshal
authors.affiliation: Department of Microbiology, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, India.
authors.forename: Ratnakar
authors.initials: R
authors.lastname: Shukla
authors.affiliation: Department of Gastroenterology, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, India.
authors.forename: Deepakshi
authors.initials: D
authors.lastname: Srivastava
authors.affiliation: Department of Gastroenterology, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, India.
authors.forename: Uday C
authors.initials: UC
authors.lastname: Ghoshal
mesh_terms: D000328:Adult; D000368:Aged; D019540:Area Under Curve; D001944:Breath Tests; D016022:Case-Control Studies; D003248:Constipation / Q000382:microbiology*; D003967:Diarrhea / Q000382:microbiology; D005243:Feces / Q000737:chemistry; D005260:Female; D006801:Humans; D043183:Irritable Bowel Syndrome / Q000150:complications / Q000382:microbiology*; D007792:Lactulose; D008297:Male; D008697:Methane / Q000032:analysis*; D041581:Methanobrevibacter / Q000502:physiology*; D008875:Middle Aged; D012372:ROC Curve; D012680:Sensitivity and Specificity; D055815:Young Adult
chemical_list: D007792:Lactulose; D008697:Methane
keywords: Gut transit; Lactulose hydrogen breath test; Methanogenic flora; Real-time polymerase chain reaction