title: Changes in antibiotic usage and susceptibility in nosocomial Enterobacteriaceae and Pseudomonas isolates following the introduction of ertapenem to hospital formulary.
abstract: There is concern that widespread usage of ertapenem may promote cross-resistance to other carbapenems. To analyse the impact that adding ertapenem to our hospital formulary had on usage of other broad-spectrum agents and on susceptibilities of nosocomial Enterobacteriaceae and Pseudomonas isolates, we performed interrupted time-series analyses to determine the change in linear trend in antibiotic usage and change in mean proportion and linear trend of susceptibility pre- (March 2004-June 2005) and post- (July 2005-December 2008) ertapenem introduction. Usage of piperacillin-tazobactam (P=0·0013) and ampicillin-sulbactam (P=0·035) declined post-ertapenem introduction. For Enterobacteriaceae, the mean proportion susceptible to ciprofloxacin (P=0·016) and piperacillin-tazobactam (P=0·038) increased, while the linear trend in susceptibility significantly increased for cefepime (P=0·012) but declined for ceftriaxone (P=0·0032). For Pseudomonas, the mean proportion susceptible to cefepime (P=0·011) and piperacillin-tazobactam (P=0·028) increased, as did the linear trend in susceptibility to ciprofloxacin (P=0·028). Notably, no significant changes in carbapenem susceptibility were observed.
authors.affiliation: Infectious Diseases Section, VA Greater Los Angeles Healthcare System, 11301 Wilshire Blvd., Los Angeles, CA 90073, USA. cgraber@ucla.edu
authors.forename: C J
authors.initials: CJ
authors.lastname: Graber
authors.forename: C
authors.initials: C
authors.lastname: Hutchings
authors.forename: F
authors.initials: F
authors.lastname: Dong
authors.forename: W
authors.initials: W
authors.lastname: Lee
authors.forename: J K
authors.initials: JK
authors.lastname: Chung
authors.forename: T
authors.initials: T
authors.lastname: Tran
mesh_terms: D000900:Anti-Bacterial Agents / Q000008:administration & dosage* / Q000494:pharmacology; D003428:Cross Infection / Q000382:microbiology*; D011307:Drug Prescriptions / Q000706:statistics & numerical data*; D024881:Drug Resistance, Bacterial / Q000187:drug effects; D004755:Enterobacteriaceae / Q000187:drug effects* / Q000302:isolation & purification; D000077727:Ertapenem; D006801:Humans; D011549:Pseudomonas / Q000187:drug effects* / Q000302:isolation & purification; D012044:Regression Analysis; D047090:beta-Lactams / Q000008:administration & dosage* / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; D047090:beta-Lactams; D000077727:Ertapenem