title: Outbreak of resistant Pseudomonas aeruginosa infections during a quarterly cycling antibiotic regimen.
abstract: BACKGROUND
  Antibiotic cycling or rotation of antimicrobial agent classes has been proposed to combat antimicrobial resistance.
  
  
  METHODS
  A prospective cohort study was conducted in a medical intensive care unit (ICU) of a university hospital between December 1, 2000, and September 30, 2002, as part of a three-center trial under the aegis of the U.S. Centers for Disease Control and Prevention. Patients admitted to the medical ICU for > 48 h were enrolled, and demographic and microbiological data were collected until discharge or death. Baseline data were collected for four months (12/1/00 to 3/31/01) and compared with data collected after institution of a quarterly cycling regimen (cycle order: Cefepime, ciprofloxacin, piperacillin-tazobactam, imipenem-cilastatin) for the empiric treatment of gram-negative infections (4/01/01 to 9/30/02).
  
  
  RESULTS
  Of 1,074 consecutive admissions, 301 were enrolled, 59 during baseline and 242 during the cycling periods. An outbreak of multi-drug resistant Pseudomonas aeruginosa followed cycle 2 (cefepime), coinciding with cycles 3 and 4 (ciprofloxacin and piperacillin-tazobactam) (80.0 and 73.7 vs. 37.3 isolates/100 patients enrolled for cycles 3/4 and baseline, respectively; p = 0.04). Acinetobacter spp. were isolated less frequently during the cycling periods (15.3 vs. 1.2 isolates/100 patients for baseline and cycling periods, respectively; p > or = 0.01). The crude hospital mortality rate was similar (24/59 [41%] baseline vs. 73/242 [30%] cycling; p = 0.16) between periods. However, the percentage of patients admitted to the medical ICU who subsequently acquired an infection followed by in-hospital death was higher at baseline than during cycling: 15/59 (25.4%) vs. 33/242 (13.6%)(p = 0.04).
  
  
  CONCLUSIONS
  In this study, the cycling strategy was not definitively associated with beneficial changes in unit epidemiology and in fact may have contributed to an outbreak of multi-drug resistant P. aeruginosa.
authors.affiliation: Department of Surgery, University of Virginia Health System, Charlottesville, VA 22908, USA. th8q@virginia.edu
authors.forename: Traci L
authors.initials: TL
authors.lastname: Hedrick
authors.forename: Alison S
authors.initials: AS
authors.lastname: Schulman
authors.forename: Shannon T
authors.initials: ST
authors.lastname: McElearney
authors.forename: Robert L
authors.initials: RL
authors.lastname: Smith
authors.forename: Brian R
authors.initials: BR
authors.lastname: Swenson
authors.forename: Heather L
authors.initials: HL
authors.lastname: Evans
authors.forename: Jonathon D
authors.initials: JD
authors.lastname: Truwit
authors.forename: W Michael
authors.initials: WM
authors.lastname: Scheld
authors.forename: Robert G
authors.initials: RG
authors.lastname: Sawyer
mesh_terms: D000368:Aged; D000900:Anti-Bacterial Agents / Q000008:administration & dosage; D003428:Cross Infection / Q000188:drug therapy* / Q000453:epidemiology / Q000517:prevention & control; D004196:Disease Outbreaks; D004334:Drug Administration Schedule; D024901:Drug Resistance, Multiple, Bacterial / Q000187:drug effects*; D005260:Female; D016905:Gram-Negative Bacterial Infections / Q000188:drug therapy*; D006801:Humans; D007362:Intensive Care Units; D008297:Male; D008875:Middle Aged; D010347:Patient Care Planning; D010349:Patient Compliance; D011446:Prospective Studies; D011552:Pseudomonas Infections / Q000453:epidemiology*; D011550:Pseudomonas aeruginosa / Q000187:drug effects*
chemical_list: D000900:Anti-Bacterial Agents