title: Obesity-associated gut microbiota is enriched in Lactobacillus reuteri and depleted in Bifidobacterium animalis and Methanobrevibacter smithii.
abstract: BACKGROUND
  Obesity is associated with increased health risk and has been associated with alterations in bacterial gut microbiota, with mainly a reduction in Bacteroidetes, but few data exist at the genus and species level. It has been reported that the Lactobacillus and Bifidobacterium genus representatives may have a critical role in weight regulation as an anti-obesity effect in experimental models and humans, or as a growth-promoter effect in agriculture depending on the strains.
  
  
  OBJECTIVE
  To confirm reported gut alterations and test whether Lactobacillus or Bifidobacterium species found in the human gut are associated with obesity or lean status, we analyzed the stools of 68 obese and 47 controls targeting Firmicutes, Bacteroidetes, Methanobrevibacter smithii, Lactococcus lactis, Bifidobacterium animalis and seven species of Lactobacillus by quantitative PCR (qPCR) and culture on a Lactobacillus-selective medium.
  
  
  RESULTS
  In qPCR, B. animalis (odds ratio (OR)=0.63; 95% confidence interval (CI) 0.39-1.01; P=0.056) and M. smithii (OR=0.76; 95% CI 0.59-0.97; P=0.03) were associated with normal weight whereas Lactobacillus reuteri (OR=1.79; 95% CI 1.03-3.10; P=0.04) was associated with obesity.
  
  
  CONCLUSIONS
  The gut microbiota associated with human obesity is depleted in M. smithii. Some Bifidobacterium or Lactobacillus species were associated with normal weight (B. animalis) while others (L. reuteri) were associated with obesity. Therefore, gut microbiota composition at the species level is related to body weight and obesity, which might be of relevance for further studies and the management of obesity. These results must be considered cautiously because it is the first study to date that links specific species of Lactobacillus with obesity in humans.
authors.affiliation: URMITE -CNRS UMR 6236 IRD 198, IFR 48, Faculté de Médecine, Université de la Méditerranée, 27 Bd Jean Moulin, Marseille, France.
authors.forename: M
authors.initials: M
authors.lastname: Million
authors.forename: M
authors.initials: M
authors.lastname: Maraninchi
authors.forename: M
authors.initials: M
authors.lastname: Henry
authors.forename: F
authors.initials: F
authors.lastname: Armougom
authors.forename: H
authors.initials: H
authors.lastname: Richet
authors.forename: P
authors.initials: P
authors.lastname: Carrieri
authors.forename: R
authors.initials: R
authors.lastname: Valero
authors.forename: D
authors.initials: D
authors.lastname: Raccah
authors.forename: B
authors.initials: B
authors.lastname: Vialettes
authors.forename: D
authors.initials: D
authors.lastname: Raoult
mesh_terms: D000328:Adult; D001644:Bifidobacterium / Q000302:isolation & purification*; D002478:Cells, Cultured; D005260:Female; D005602:France; D041981:Gastrointestinal Tract / Q000382:microbiology* / Q000503:physiopathology; D006801:Humans; D007249:Inflammation / Q000382:microbiology* / Q000503:physiopathology*; D052200:Limosilactobacillus reuteri / Q000302:isolation & purification*; D008297:Male; D041581:Methanobrevibacter / Q000302:isolation & purification*; D008875:Middle Aged; D009765:Obesity / Q000382:microbiology* / Q000503:physiopathology; D011795:Surveys and Questionnaires