title: Methanobrevibacter smithii is the predominant methanogen in patients with constipation-predominant IBS and methane on breath.
abstract: OBJECTIVE
  Among irritable bowel syndrome (IBS) patients, breath methane producers overwhelmingly have constipation predominance (C-IBS). Although the most common methanogen in humans is Methanobrevibacter smithii, incidence and type of methanogenic bacteria in C-IBS patients are unknown.
  
  
  METHODS
  By use of a questionnaire and lactulose breath testing, subjects with Rome II C-IBS and methane (>3 ppm) were selected (n = 9). The control group included subjects with IBS who had no breath methane (n = 10). Presence of bacterial DNA was assessed in a stool sample of each subject by quantitative-PCR using universal 16S rDNA primer. M. smithii was quantified by use of a specific rpoB gene primer.
  
  
  RESULTS
  M. smithii was detected in both methane and non-methane subjects. However, counts and relative proportion of M. smithii were significantly higher for methane-positive than for methane-negative subjects (1.8 × 10(7) ± 3.0 × 10(7) vs 3.2 × 10(5) ± 7.6 × 10(5) copies/g wet stool, P < 0.001; and 7.1 ± 6.3 % vs 0.24 ± 0.47 %, P = 0.02 respectively). The minimum threshold of M. smithii resulting in positive lactulose breath testing for methane was 4.2 × 10(5) copies/g wet stool or 1.2 % of total stool bacteria. Finally, area-under-curve for breath methane correlated significantly with both absolute quantity and percentage of M. smithii in stool (R = 0.76; P < 0.001 and R = 0.77; P < 0.001 respectively).
  
  
  CONCLUSIONS
  M. smithii is the predominant methanogen in C-IBS patients with methane on breath testing. The number and proportion of M. smithii in stool correlate well with amount of breath methane.
authors.affiliation: GI Motility Program, Division of Gastroenterology, Cedars Sinai Medical Center, 8730, Alden Dr, Suite 225 E, Los Angeles, CA 90048, USA.
authors.forename: Gene
authors.initials: G
authors.lastname: Kim
authors.forename: Fnu
authors.initials: F
authors.lastname: Deepinder
authors.forename: Walter
authors.initials: W
authors.lastname: Morales
authors.forename: Laura
authors.initials: L
authors.lastname: Hwang
authors.forename: Stacy
authors.initials: S
authors.lastname: Weitsman
authors.forename: Christopher
authors.initials: C
authors.lastname: Chang
authors.forename: Robert
authors.initials: R
authors.lastname: Gunsalus
authors.forename: Mark
authors.initials: M
authors.lastname: Pimentel
mesh_terms: D000328:Adult; D001944:Breath Tests; D003248:Constipation / Q000209:etiology* / Q000382:microbiology; D004269:DNA, Bacterial / Q000235:genetics; D005243:Feces / Q000382:microbiology; D005260:Female; D006801:Humans; D006859:Hydrogen / Q000378:metabolism; D043183:Irritable Bowel Syndrome / Q000150:complications / Q000382:microbiology*; D008297:Male; D008697:Methane / Q000096:biosynthesis*; D041581:Methanobrevibacter / Q000145:classification* / Q000378:metabolism*; D008875:Middle Aged; D012329:RNA, Bacterial / Q000235:genetics; D012336:RNA, Ribosomal, 16S / Q000235:genetics
chemical_list: D004269:DNA, Bacterial; D012329:RNA, Bacterial; D012336:RNA, Ribosomal, 16S; D006859:Hydrogen; D008697:Methane