title: Selective decontamination of the digestive tract: the mechanism of action is control of gut overgrowth.
abstract: OBJECTIVE
  Gut overgrowth is the pathophysiological event in the critically ill requiring intensive care. In relation to the risk of developing a clinically important outcome, gut overgrowth is defined as ≥10(5) potential pathogens including 'abnormal' aerobic Gram-negative bacilli (AGNB), 'normal' bacteria and yeasts, per mL of digestive tract secretion. Surveillance samples of throat and gut are the only samples to detect overgrowth. Gut overgrowth is the crucial event which precedes both primary and secondary endogenous infection, and a risk factor for the development of de novo resistance. Selective decontamination of the digestive tract (SDD) is an antimicrobial prophylaxis designed to control overgrowth.
  
  
  METHODS
  There have been 65 randomised controlled trials of SDD in 15,000 patients over 25 years and 11 meta-analyses, which are reviewed.
  
  
  CONCLUSIONS
  These trials demonstrate that the full SDD regimen using parenteral and enteral antimicrobials reduces lower airway infection by 72 %, blood stream infection by 37 %, and mortality by 29 %. Resistance is also controlled. Parenteral cefotaxime which reaches high salivary and biliary concentrations eradicates overgrowth of 'normal' bacteria such as Staphylococcus aureus in the throat. Enteral polyenes control 'normal' Candida species. Enteral polymyxin and tobramycin, eradicate, or prevent gut overgrowth of 'abnormal' AGNB. Enteral vancomycin controls overgrowth of 'abnormal' methicillin-resistant S. aureus. SDD controls overgrowth by achieving high antimicrobial concentrations effective against 'normal' and 'abnormal' potential pathogens rather than by selectivity.
authors.affiliation: Department of Emergency, Unit of Anesthesia and Intensive Care, Presidio Ospedaliero di Gorizia, Via Fatebenefratelli 34, 34170, Gorizia, Italy.
authors.forename: Luciano
authors.initials: L
authors.lastname: Silvestri
authors.forename: Miguel A
authors.initials: MA
authors.lastname: de la Cal
authors.forename: Hendrick K F
authors.initials: HK
authors.lastname: van Saene
mesh_terms: D019072:Antibiotic Prophylaxis; D001424:Bacterial Infections / Q000517:prevention & control*; D002353:Carrier State / Q000175:diagnosis / Q000188:drug therapy*; D016638:Critical Illness; D003666:Decontamination / Q000379:methods*; D004064:Digestive System / Q000382:microbiology*; D006088:Gram-Negative Aerobic Bacteria / Q000254:growth & development; D006801:Humans; D015201:Meta-Analysis as Topic; D016032:Randomized Controlled Trials as Topic