title: Depletion of murine intestinal microbiota: effects on gut mucosa and epithelial gene expression.
abstract: BACKGROUND
  Inappropriate cross talk between mammals and their gut microbiota may trigger intestinal inflammation and drive extra-intestinal immune-mediated diseases. Epithelial cells constitute the interface between gut microbiota and host tissue, and may regulate host responses to commensal enteric bacteria. Gnotobiotic animals represent a powerful approach to study bacterial-host interaction but are not readily accessible to the wide scientific community. We aimed at refining a protocol that in a robust manner would deplete the cultivable intestinal microbiota of conventionally raised mice and that would prove to have significant biologic validity.
  
  
  RESULTS
  Previously published protocols for depleting mice of their intestinal microbiota by administering broad-spectrum antibiotics in drinking water were difficult to reproduce. We show that twice daily delivery of antibiotics by gavage depleted mice of their cultivable fecal microbiota and reduced the fecal bacterial DNA load by 400 fold while ensuring the animals' health. Mice subjected to the protocol for 17 days displayed enlarged ceca, reduced Peyer's patches and small spleens. Antibiotic treatment significantly reduced the expression of antimicrobial factors to a level similar to that of germ-free mice and altered the expression of 517 genes in total in the colonic epithelium. Genes involved in cell cycle were significantly altered concomitant with reduced epithelial proliferative activity in situ assessed by Ki-67 expression, suggesting that commensal microbiota drives cellular proliferation in colonic epithelium.
  
  
  CONCLUSIONS
  We present a robust protocol for depleting conventionally raised mice of their cultivatable intestinal microbiota with antibiotics by gavage and show that the biological effect of this depletion phenocopies physiological characteristics of germ-free mice.
authors: Department of Pathology and Centre for Immune Regulation, University of Oslo, Oslo, Norway. dag.henrik.reikvam@rr-research.no
authors: Dag Henrik
authors: DH
authors: Reikvam
authors: Alexander
authors: A
authors: Erofeev
authors: Anders
authors: A
authors: Sandvik
authors: Vedrana
authors: V
authors: Grcic
authors: Frode Lars
authors: FL
authors: Jahnsen
authors: Peter
authors: P
authors: Gaustad
authors: Kathy D
authors: KD
authors: McCoy
authors: Andrew J
authors: AJ
authors: Macpherson
authors: Leonardo A
authors: LA
authors: Meza-Zepeda
authors: Finn-Eirik
authors: FE
authors: Johansen
mesh_terms: D000818:Animals; D004847:Epithelial Cells / Q000378:metabolism; D005786:Gene Expression Regulation; D005856:Germ-Free Life; D007413:Intestinal Mucosa / Q000378:metabolism; D007422:Intestines / Q000382:microbiology*; D051379:Mice; D020133:Reverse Transcriptase Polymerase Chain Reaction