title: Effects of reducing beta-lactam antibiotic pressure on intestinal  colonization of antibiotic-resistant gram-negative bacteria.
abstract: BACKGROUND
  We determined the effects of two antibiotic policies (predominance of either beta-lactam antibiotics or fluroquinolones) on acquisition with third-generation cephalosporin-resistant Enterobacteriaceae (CRE) and fluoroquinolone-resistant CRE (FCRE) in two ICUs, with monitoring of other variables that may influence acquisition.
  
  
  METHODS
  After an 8-month baseline period, units were randomized to a predominant beta-lactam antibiotic regimen (weekly cycling of ceftriaxone, amoxicillin-clavulanic acid and fluroquinolones) or a fluoroquinolone regimen for 3 months, with cross-over for another 3 months. Acquisition of CRE and FCRE was determined by microbiological surveillance.
  
  
  RESULTS
  During baseline, acquisition rates for CRE and FCRE were 14/1,000 and 2/1,000 patient days at risk, respectively. Cross-transmission of CRE accounted for <or=25% of acquisitions, and CRE acquisition was associated with the use of beta-lactam antibiotics (amoxicillin-clavulanic acid in particular). As compared to baseline, beta-lactam antibiotic use [in defined daily dose (DDD)/1,000 patient days] was reduced from 854 to 526 (-39%) and 555 (-35%) during both intervention periods. Fluoroquinolone use was increased from 150 and 129 DDD/1,000 patient days in baseline and the beta-lactam period to 514 DDD/1,000 patient days (+243%) in the fluoroquinolone period. Reductions in beta-lactam use were not associated with reduced CRE acquisition [adjusted HRs were 1.0 (95% CR: 0.5-2.2) and 1.1 (95% CI: 0.5-2.5) during both periods, respectively]. Increased use of fluoroquinolones was associated with increased acquisition of FCRE [adjusted HR 4.1 (95% CI: 1.4-11.9; p < 0.01]. Infection control variables remained comparable during all periods.
  
  
  CONCLUSIONS
  A 35-39% reduction of beta-lactam exposure was not associated with reduced acquisition of CRE, whereas a 243% increase of fluoroquinolone use increased acquisition of FCRE.
authors.affiliation: Department of Medical Microbiology, St. Elisabethziekenhuis, Hilvarenbeekse Weg 60, 5022 GC Tilburg, The Netherlands.
authors.forename: Saskia
authors.initials: S
authors.lastname: Nijssen
authors.forename: Ad
authors.initials: A
authors.lastname: Fluit
authors.forename: David
authors.initials: D
authors.lastname: van de Vijver
authors.forename: Janetta
authors.initials: J
authors.lastname: Top
authors.forename: Rob
authors.initials: R
authors.lastname: Willems
authors.forename: Marc J M
authors.initials: MJ
authors.lastname: Bonten
mesh_terms: D000328:Adult; D000368:Aged; D000900:Anti-Bacterial Agents / Q000627:therapeutic use*; D002511:Cephalosporins / Q000627:therapeutic use; D003428:Cross Infection / Q000517:prevention & control; D018592:Cross-Over Studies; D024881:Drug Resistance, Bacterial / Q000187:drug effects; D004755:Enterobacteriaceae / Q000187:drug effects; D005260:Female; D024841:Fluoroquinolones / Q000627:therapeutic use; D006088:Gram-Negative Aerobic Bacteria / Q000187:drug effects*; D006801:Humans; D017053:Infection Control; D007362:Intensive Care Units; D007422:Intestines / Q000382:microbiology*; D008297:Male; D008875:Middle Aged; D009426:Netherlands; D011050:Policy Making; D018440:beta-Lactam Resistance / Q000187:drug effects*
chemical_list: D000900:Anti-Bacterial Agents; D002511:Cephalosporins; D024841:Fluoroquinolones