title: Use of probiotics to correct dysbiosis of normal microbiota following disease or disruptive events: a systematic review.
abstract: OBJECTIVE
  To assess the evidence for the claim probiotics can correct dysbiosis of the normal microbiota resulting from disease or disruptive events.
  
  
  METHODS
  Systematic review of published clinical trials of patients receiving a probiotic intervention for the prevention or treatment of various diseases.
  
  
  METHODS
  Sources searched (1985-2013): PubMed, EMBASE, Cochrane Database of Systematic Reviews, CINAHL, AMED and ISI Web of Science. Three on-line clinical trial registries were searched: Cochrane Central Register of Controlled trials, MetaRegister of Controlled Trials and National Institutes of Health.
  
  
  METHODS
  Included studies were randomised clinical trials of probiotic interventions having microbiological assays. Studies were evaluated following Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines for specific probiotic strains. A standard data extraction form was used to collect the raw data.
  
  
  METHODS
  The primary outcome is the degree of microbiota correction by specific probiotic strains. Secondary outcome was the association between the degree of dysbiosis correction and clinical efficacy.
  
  
  RESULTS
  The review of the literature found three distinct study designs: model A (restoration) assayed patients enrolled with a healthy, undisturbed microbiota and then assayed postdisruptive event and probiotic therapy; model B (alteration) assayed patients with pre-existing disrupted microbiota and then postprobiotic therapy; model C (no dysbiosis) assayed volunteers with no disruptive event prebiotic and postprobiotic. From a total of 63 trials, 83% of the probiotic products using model A restored the microbiota, 56% using model B improved the microbiota and only 21% using model C had any effect on microbiota. Clinical efficacy was more commonly associated with strains capable of restoration of the normal microbiota.
  
  
  CONCLUSIONS
  The ability to assess the degree of dysbiosis improvement is dependent on the enrolled population and the timing of microbiological assays. The functional claim for correcting dysbiosis is poorly supported for most probiotic strains and requires further research.
  
  
  BACKGROUND
  PROSPERO (CRD42014007224).
authors.affiliation: Department of Medicinal Chemistry, School of Pharmacy, University of Washington, Seattle, Washington, USA.
authors.forename: Lynne V
authors.initials: LV
authors.lastname: McFarland
mesh_terms: D004194:Disease; D064806:Dysbiosis / Q000188:drug therapy*; D006801:Humans; D064307:Microbiota / Q000187:drug effects*; D019936:Probiotics / Q000627:therapeutic use*; D012720:Severity of Illness Index; D016896:Treatment Outcome
keywords: Clinical Pharmacology