title: Selection of resistance during sequential use of preferential antibiotic classes.
abstract: OBJECTIVE
  To determine the effect of antibiotic class pressure on the susceptibility of bacteria during sequential periods of antibiotic homogeneity.
  
  
  METHODS
  Prospective study in a mixed ICU with three separated subunits of eight, eight, and ten beds.
  
  
  METHODS
  The study examined the 1,721 patients with a length of stay longer than 2 days.
  
  
  METHODS
  Three different antibiotic regimens were used sequentially over 2 years as first-choice empirical treatment: cephalosporins, fluoroquinolone, or a penicillin-beta-lactamase inhibitor combination. Each regimen was applied for 8 months in each subunits of the ICU, using "latin square" design.
  
  
  RESULTS
  We treated 731 infections in 546 patients (32% of patients staying more than 48 h). There were 25.5 ICU-acquired infections per 1,000 patient-days. Infecting pathogens and colonizing bacteria were found in 2,739 samples from 1,666 patients (96.8%). No significant change in global antibiotic susceptibility was observed over time. However, a decrease in the susceptibility of several species was observed for antibiotics used as the first-line therapy in the unit. Selection pressure of antibiotics and occurrence of resistance during treatment was documented within an 8-month rotation period.
  
  
  CONCLUSIONS
  Antibiotic use for periods of several months induces bacterial resistance in common pathogens.
authors.affiliation: Department of General Intensive Care, University Hospital Center, Domaine Universitaire du Sart-Tilman, 4000 Liège, Belgium. pdamas@chu.ulg.ac.be
authors.forename: Pierre
authors.initials: P
authors.lastname: Damas
authors.forename: Jean-Luc
authors.initials: JL
authors.lastname: Canivet
authors.forename: Didier
authors.initials: D
authors.lastname: Ledoux
authors.forename: Mehran
authors.initials: M
authors.lastname: Monchi
authors.forename: Pierrette
authors.initials: P
authors.lastname: Melin
authors.forename: Monique
authors.initials: M
authors.lastname: Nys
authors.forename: Patrick
authors.initials: P
authors.lastname: De Mol
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology / Q000627:therapeutic use*; D001530:Belgium; D002511:Cephalosporins / Q000494:pharmacology / Q000627:therapeutic use; D004338:Drug Combinations; D024881:Drug Resistance, Bacterial; D004363:Drug Utilization; D024841:Fluoroquinolones / Q000494:pharmacology / Q000627:therapeutic use; D006801:Humans; D017053:Infection Control / Q000379:methods*; D007362:Intensive Care Units; D008875:Middle Aged; D010406:Penicillins / Q000494:pharmacology / Q000627:therapeutic use; D011446:Prospective Studies; D065093:beta-Lactamase Inhibitors
chemical_list: D000900:Anti-Bacterial Agents; D002511:Cephalosporins; D004338:Drug Combinations; D024841:Fluoroquinolones; D010406:Penicillins; D065093:beta-Lactamase Inhibitors