Differences in antimicrobial susceptibility in Escherichia coli from Canadian intensive care units based on regional and demographic variables.

OBJECTIVES: Escherichia coli resistance to antimicrobials varies according to many factors. E coli isolates from Canadian intensive care units (ICUs) were studied to determine the distribution and demographics associated with antimicrobial resistance in this population.
METHODS: The Canadian National Intensive Care Unit (CAN-ICU) study characterized pathogens isolated in Canadian ICUs from July 2005 to June 2006. E coli susceptibility to 10 antimicrobials was determined and a multivariate logistic regression model was designed to determine whether region, sex, isolation from a sterile site and age (younger than 30 years) were significantly associated with susceptibility to the tested antimicrobials, to multidrug resistance or pan-susceptibility.
RESULTS: Four hundred ninety-three E coli isolates, representing 12.6% of all isolates collected in the CAN-ICU study were examined. Susceptibilities were highest for meropenem and tigecycline (100%), cefepime (98.2%), piperacillin-tazobactam (97.0%), ceftriaxone (93.1%) and gentamicin (92.3%), and lowest for cefazolin (76.7%), trimethoprim-sulfamethoxazole (75.7%) and the fluoroquinolones (ciprofloxacin, 78.3%; and levofloxacin, 78.9%). In the multivariate model, fluoroquinolone resistance was lowest in patients younger than 30 years of age. Cefazolin and ceftriaxone susceptibility was lowest in Nova Scotia. Susceptibility to all tested antimicrobials was lowest in Nova Scotia and British Columbia. Isolation from a sterile site was associated with trimethoprim-sulfamethoxazole, piperacillin-tazobactam and multidrug resistance.
CONCLUSIONS: E coli antimicrobial susceptibility varies across Canadian ICUs. Age, region and site of infection should be considered when prescribing empirical antimicrobial therapy. For infections caused by or suspected to be caused by E coli, fluoroquinolones, cefazolin and sulfonamides should be avoided due to low susceptibilities. Local antimicrobial prescribing practices, in particular the liberal use of fluoroquinolones and cephalosporins, and inadequate infection control practices are likely reducing susceptibility rates.