title: Clostridium difficilecolonization and antibiotics response in PolyFermS continuous model mimicking elderly intestinal fermentation.
abstract: BACKGROUND
  Clostridium difficile(CD), a spore-forming and toxin-producing bacterium, is the main cause for antibiotic-associated diarrhea in the elderly. Here we investigated CD colonization in novel in vitro fermentation models inoculated with immobilized elderly fecal microbiota and the effects of antibiotic treatments.
  
  
  METHODS
  Two continuous intestinal PolyFermS models inoculated with different immobilized elder microbiota were used to investigate selected factors of colonization of CD in proximal (PC, model 1) and transverse-distal (TDC, model 1 and 2) colon conditions. Colonization of two CD strains of different PCR ribotypes, inoculated as vegetative cells (ribotype 001, model 1) or spores (ribotypes 001 and 012, model 2), was tested. Treatments with two antibiotics, ceftriaxone (daily 150 mg L-1) known to induce CD infection in vivo or metronidazole (twice daily 333 mg L-1) commonly used to treat CD, were investigated in TDC conditions (model 2) for their effects on gut microbiota composition (qPCR, 16S pyrosequencing) and activity (HPLC), CD spore germination and colonization, and cytotoxin titer (Vero cell assay).
  
  
  RESULTS
  CD remained undetected after inoculating vegetative cells in PC reactors of model 1, but was shown to colonize TDC reactors of both models, reaching copy numbers of up to log108 mL-1effluent with stable production of toxin correlating with CD cell numbers. Ceftriaxone treatment in TDC reactors showed only small effects on microbiota composition and activity and did not promote CD colonization compared to antibiotic-free control reactor. In contrast, treatment with metronidazole after colonization of CD induced large modifications in the microbiota and decreased CD numbers below the detection limit of the specific qPCR. However, a fast CD recurrence was measured only 2 days after cessation of metronidazole treatment.
  
  
  CONCLUSIONS
  Using our in vitro fermentation models, we demonstrated that stable CD colonization in TDC reactors can be induced by inoculating CD vegetative cells or spores without the application of ceftriaxone. Treatment with metronidazole temporarily reduced the counts of CD, in agreement with CD infection recurrence in vivo. Our data demonstrate that CD colonized an undisturbed microbiota in vitro, in contrast to in vivo observations, thus suggesting an important contribution of host-related factors in the protection against CD infection.
authors.affiliation: Laboratory of Food Biotechnology, Institute of Food, Nutrition and Health, ETH Zurich, Schmelzbergstrasse 7, 8092 Zurich, Switzerland.
authors.forename: Sophie
authors.initials: S
authors.lastname: Fehlbaum
authors.affiliation: Laboratory of Food Biotechnology, Institute of Food, Nutrition and Health, ETH Zurich, Schmelzbergstrasse 7, 8092 Zurich, Switzerland.
authors.forename: Christophe
authors.initials: C
authors.lastname: Chassard
authors.affiliation: Laboratory of Food Biotechnology, Institute of Food, Nutrition and Health, ETH Zurich, Schmelzbergstrasse 7, 8092 Zurich, Switzerland.
authors.forename: Sophie Annick
authors.initials: SA
authors.lastname: Poeker
authors.affiliation: Danone Nutricia Research, Palaiseau Cédex, France.
authors.forename: Muriel
authors.initials: M
authors.lastname: Derrien
authors.affiliation: Danone Nutricia Research, Palaiseau Cédex, France.
authors.forename: Candice
authors.initials: C
authors.lastname: Fourmestraux
authors.affiliation: Laboratory of Food Biotechnology, Institute of Food, Nutrition and Health, ETH Zurich, Schmelzbergstrasse 7, 8092 Zurich, Switzerland.
authors.forename: Christophe
authors.initials: C
authors.lastname: Lacroix
keywords: Antibiotics; Ceftriaxone; Clostridium difficile; Elderly gut microbiota; In vitro model; Intestinal fermentation; Metronidazole