title: Change in antipseudomonal carbapenem susceptibility in 25 hospitals across 9 years is not associated with the use of ertapenem.
abstract: BACKGROUND
  Concern remains that ertapenem use may promote cross-resistance in Pseudomonas aeruginosa to antipseudomonal carbapenems (APCs). This study extends our earlier multicentre investigation of this relationship by an additional 3 years.
  
  
  METHODS
  Use density ratios (UDRs) for ertapenem, APCs, aminoglycosides, fluoroquinolones and non-carbapenem β-lactams were derived from purchase data for 3 years pre-adoption and up to 6 years post-adoption of ertapenem at 25 hospitals. Hospital antibiograms in corresponding years yielded APC susceptibility data. Mixed model repeated measures ANOVA explored associations between 9 year repeated APC susceptibility and ertapenem UDR while controlling for all other classes.
  
  
  RESULTS
  All 25 sites had 4 years of post-adoption data, with 22 of 25 reporting 5 years and 18 of 25 reporting 6 years. Ertapenem UDR rose steadily once adopted, with a mean UDR of 7.27 in year 4 and a mean UDR of 15.93 in year 9. APC UDR increased initially (from 10.39 in year 1 to a peak of 18.77 in year 6) and then declined to 15.27 in year 9. By year 9 ertapenem and APC use were similar. Among other classes, fluoroquinolone UDR increased notably (year/mean UDR): 1/303.84; 4/174.38; and 9/423.32. Mean APC susceptibility declined from 85.4% in year 1 to 81.0% in year 9; this change across time was not significant (P = 0.99). Change in 9 year APC susceptibility was not associated with ertapenem UDR (P = 0.54), while controlling for all other antibiotic classes (all showed no association at P > 0.5).
  
  
  CONCLUSIONS
  While controlling for utilization of other antibiotic classes, we found no association between change in APC susceptibility and ertapenem use.
authors: Center for Anti-Infective Research and Development, Hartford Hospital, Hartford, CT, USA.
authors: Kathryn J
authors: KJ
authors: Eagye
authors: David P
authors: DP
authors: Nicolau
mesh_terms: D000900:Anti-Bacterial Agents / Q000008:administration & dosage* / Q000494:pharmacology*; D015780:Carbapenems / Q000494:pharmacology*; D004363:Drug Utilization / Q000706:statistics & numerical data; D000077727:Ertapenem; D006761:Hospitals; D006801:Humans; D008826:Microbial Sensitivity Tests; D011552:Pseudomonas Infections / Q000188:drug therapy*; D011550:Pseudomonas aeruginosa / Q000187:drug effects* / Q000302:isolation & purification; D018440:beta-Lactam Resistance; D047090:beta-Lactams / Q000008:administration & dosage*
chemical_list: D000900:Anti-Bacterial Agents; D015780:Carbapenems; D047090:beta-Lactams; D000077727:Ertapenem