title: Evaluating the Impact of Antibiotic Exposures as Time-Dependent Variables on the Acquisition of Carbapenem-Resistant Acinetobacter baumannii.
abstract: OBJECTIVE
  To determine the time-dependent effect of antibiotics on the initial acquisition of carbapenem-resistant Acinetobacter baumannii.
  
  
  METHODS
  Retrospective cohort study.
  
  
  METHODS
  Forty-bed trauma ICU in Miami, FL.
  
  
  METHODS
  All consecutive patients admitted to the unit from November 1, 2010, to November 30, 2011.
  
  
  METHODS
  None.
  
  
  RESULTS
  Patients underwent surveillance cultures at admission to the unit and weekly thereafter. The primary outcome was the acquisition of carbapenem-resistant A. baumannii on surveillance cultures. Daily antibiotic exposures during the time of observation were used to construct time-dependent variables, including cumulative exposures (in grams and daily observed doses [defined daily doses]). Among 360 patients, 45 (12.5%) became colonized with carbapenem-resistant A. baumannii. Adjusted Cox models showed that each additional point in the Acute Physiologic and Chronic Health Evaluation score increased the hazard by 4.8% (hazard ratio, 1.048; 95% CI, 1.010-1.087; p = 0.0124) and time-dependent exposure to carbapenems quadrupled the hazard (hazard ratio, 4.087; 95% CI, 1.873-8.920; p = 0.0004) of acquiring carbapenem-resistant A. baumannii. Additionally, adjusted Cox models determined that every additional carbapenem defined daily dose increased the hazard of acquiring carbapenem-resistant A. baumannii by 5.1% (hazard ratio, 1.051; 95% CI, 1.007-1.093; p = 0.0243).
  
  
  CONCLUSIONS
  Carbapenem exposure quadrupled the hazards of acquiring A. baumannii even after controlling for severity of illness.
authors.affiliation: 1Institute for Health and Society, Medical College of Wisconsin, Milwaukee, WI.2Department of Medicine, Medical College of Wisconsin, Milwaukee, WI.3Department of Medicine, Jackson Memorial Hospital, Miami, FL.4Division of Infectious Diseases, University of Miami Miller School of Medicine, Miami, FL.5Department of Medicine, Orlando Health System and South Lake Hospital, Clermont, FL.6Department of Surgery, University of Miami Miller School of Medicine, Miami, FL.
authors.forename: L Silvia
authors.initials: LS
authors.lastname: Munoz-Price
authors.forename: Rossana
authors.initials: R
authors.lastname: Rosa
authors.forename: Jose G
authors.initials: JG
authors.lastname: Castro
authors.forename: Panthipa
authors.initials: P
authors.lastname: Laowansiri
authors.forename: Rachel
authors.initials: R
authors.lastname: Latibeaudiere
authors.forename: Nicholas
authors.initials: N
authors.lastname: Namias
authors.forename: Sergey
authors.initials: S
authors.lastname: Tarima
mesh_terms: D018806:APACHE; D000151:Acinetobacter Infections / Q000188:drug therapy / Q000453:epidemiology*; D040981:Acinetobacter baumannii / Q000187:drug effects*; D000328:Adult; D000367:Age Factors; D000900:Anti-Bacterial Agents / Q000008:administration & dosage / Q000494:pharmacology; D015780:Carbapenems / Q000008:administration & dosage / Q000494:pharmacology*; D015897:Comorbidity; D024881:Drug Resistance, Bacterial / Q000187:drug effects*; D005260:Female; D005431:Florida; D006801:Humans; D007362:Intensive Care Units / Q000706:statistics & numerical data*; D008297:Male; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D012189:Retrospective Studies; D012737:Sex Factors; D013997:Time Factors
chemical_list: D000900:Anti-Bacterial Agents; D015780:Carbapenems