title: Probiotics and synbiotics for the prevention of postoperative infections following abdominal surgery: a systematic review and meta-analysis of randomized controlled trials.
abstract: BACKGROUND
  Postoperative infections, particularly surgical site infections (SSIs), cause significant morbidity and mortality. Probiotics or synbiotics are a potential prevention strategy.
  
  
  OBJECTIVE
  To evaluate the efficacy of probiotics/synbiotics for reducing postoperative infection risk following abdominal surgery.
  
  
  METHODS
  We searched AMED, Central, CINAHL, Embase, Medline, and grey literature for randomized controlled trials of elective abdominal surgery patients administered probiotics or synbiotics compared to placebo or standard care. Primary outcome was SSIs. Secondary outcomes were adverse events, respiratory tract infections (RTIs), urinary tract infections (UTIs), combined infections, length of hospital stay, and mortality. Using random-effects meta-analyses, we estimated the relative risk (RR) or mean difference (MD) and 95% confidence interval (CI). Tests were performed for heterogeneity, subgroup and sensitivity analyses were conducted, and the overall evidence quality was graded.
  
  
  RESULTS
  We identified 20 trials (N = 1374 participants) reporting postoperative infections. Probiotics/synbiotics reduced SSIs (RR: 0.63; 95% CI: 0.41-0.98; N = 15 studies), UTIs (RR: 0.29; 95% CI: 0.15-0.57; N = 11), and combined infections (RR: 0.49; 95% CI: 0.35-0.70; N = 18). There was no difference between groups for adverse events (RR: 0.89; 95% CI: 0.61-1.30; N = 6), RTIs (RR: 0.60; 95% CI: 0.36-1.00; N = 14), length of stay (MD: -1.19; 95% CI: -2.94 to 0.56; N = 12), or mortality (RR: 1.20; 95% CI: 0.58-2.48; N = 15).
  
  
  CONCLUSIONS
  Our review suggests that probiotics/synbiotics reduce SSIs and UTIs from abdominal surgeries compared to placebo or standard of care, without evidence of safety risk. Overall study quality was low, owing mostly to imprecision (few patients and events, or wide CIs); thus larger multi-centered trials are needed to further assess the certainty in this estimate.
authors.affiliation: Department of Clinical Epidemiology and Biostatistics, McMaster University, Hamilton, Canada; Systematic Overviews through Advancing Research Technology, Child Health Evaluative Sciences, The Research Institute, The Hospital For Sick Children, Toronto, Canada.
authors.forename: L
authors.initials: L
authors.lastname: Lytvyn
authors.affiliation: Department of Clinical Epidemiology and Biostatistics, McMaster University, Hamilton, Canada.
authors.forename: K
authors.initials: K
authors.lastname: Quach
authors.affiliation: Health Sciences Library, McMaster University, Hamilton, Canada.
authors.forename: L
authors.initials: L
authors.lastname: Banfield
authors.affiliation: Department of Clinical Epidemiology and Biostatistics, McMaster University, Hamilton, Canada; Systematic Overviews through Advancing Research Technology, Child Health Evaluative Sciences, The Research Institute, The Hospital For Sick Children, Toronto, Canada; Institute of Health Policy, Management and Evaluation, Dalla Lana School of Public Health, University of Toronto, Toronto, Canada; Department of Anaesthesia and Pain Medicine, The Hospital for Sick Children, Toronto, Canada.
authors.forename: B C
authors.initials: BC
authors.lastname: Johnston
authors.affiliation: Department of Clinical Epidemiology and Biostatistics, McMaster University, Hamilton, Canada; Department of Medicine, McMaster University, Hamilton, Canada; Department of Pathology and Molecular Medicine, McMaster University, Hamilton, Canada; Michael G. DeGroote Institute for Infectious Diseases Research, McMaster University, Hamilton, Canada. Electronic address: mertzd@mcmaster.ca.
authors.forename: D
authors.initials: D
authors.lastname: Mertz
mesh_terms: D006801:Humans; D059413:Intraabdominal Infections / Q000517:prevention & control*; D010919:Placebos / Q000008:administration & dosage; D019936:Probiotics / Q000008:administration & dosage*; D016032:Randomized Controlled Trials as Topic; D013530:Surgical Wound Infection / Q000517:prevention & control*; D058616:Synbiotics / Q000008:administration & dosage*; D016896:Treatment Outcome
chemical_list: D010919:Placebos
keywords: Abdominal surgery; Postsurgical infections; Prevention; Probiotics; Surgical site infections; Synbiotics