title: Antimicrobial co-resistance patterns of gram-negative bacilli isolated from bloodstream infections: a longitudinal epidemiological study from 2002-2011.
abstract: BACKGROUND
  Increasing multidrug resistance in gram-negative bacilli (GNB) infections poses a serious threat to public health. Few studies have analyzed co-resistance rates, defined as an antimicrobial susceptibility profile in a subset already resistant to one specific antibiotic. The epidemiologic and clinical utility of determining co-resistance rates are analyzed and discussed.
  
  
  METHODS
  A 10-year retrospective study from 2002-2011 of bloodstream infections with GNB were analyzed from three hospitals in Greater Vancouver, BC, Canada. Descriptive statistics were calculated for antimicrobial resistance and co-resistance. Statistical analysis further described temporal trends of antimicrobial resistance, correlations of resistance between combinations of antimicrobials, and temporal trends in co-resistance patterns.
  
  
  RESULTS
  The total number of unique blood stream isolates of GNB was 3280. Increasing resistance to individual antimicrobials was observed for E. coli, K. pneumoniae, K. oxytoca, E. cloacae, and P. aeruginosa. Ciprofloxacin resistance in E. coli peaked in 2006 at 40% and subsequently stabilized at 29% in 2011, corresponding to decreasing ciprofloxacin usage after 2007, as assessed by defined daily dose utilization data. High co-resistance rates were observed for ceftriaxone-resistant E. coli with ciprofloxacin (73%), ceftriaxone-resistant K. pneumoniae with trimethoprim-sulfamethoxazole (83%), ciprofloxacin-resistant E. cloacae with ticarcillin-clavulanate (91%), and piperacillin-tazobactam-resistant P. aeruginosa with ceftazidime (83%).
  
  
  CONCLUSIONS
  Increasing antimicrobial resistance was demonstrated over the study period, which may partially be associated with antimicrobial consumption. The study of co-resistance rates in multidrug resistant GNB provides insight into the epidemiology of resistance acquisition, and may be used as a clinical tool to aid prescribing empiric antimicrobial therapy.
authors.affiliation: Division of Infectious Diseases, Department of Medicine, Faculty of Medicine, The University of British Columbia (UBC), 452D, Heather Pavilion East, VGH, 2733 Heather Street, Vancouver, BC V5Z 3J5, Canada. phpwong@mail.ubc.ca.
authors.forename: Patrick H P
authors.initials: PH
authors.lastname: Wong
authors.forename: Marcus
authors.initials: M
authors.lastname: von Krosigk
authors.forename: Diane L
authors.initials: DL
authors.lastname: Roscoe
authors.forename: Tim T Y
authors.initials: TT
authors.lastname: Lau
authors.forename: Masoud
authors.initials: M
authors.lastname: Yousefi
authors.forename: William R
authors.initials: WR
authors.lastname: Bowie
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology* / Q000627:therapeutic use; D016470:Bacteremia / Q000188:drug therapy / Q000453:epidemiology / Q000382:microbiology*; D001955:British Columbia / Q000453:epidemiology; D002939:Ciprofloxacin / Q000494:pharmacology* / Q000627:therapeutic use; D024881:Drug Resistance, Bacterial; D016972:Enterobacter cloacae / Q000187:drug effects / Q000302:isolation & purification; D004926:Escherichia coli / Q000187:drug effects / Q000302:isolation & purification; D016905:Gram-Negative Bacterial Infections / Q000188:drug therapy / Q000453:epidemiology / Q000382:microbiology*; D006801:Humans; D041121:Klebsiella oxytoca / Q000187:drug effects / Q000302:isolation & purification; D007711:Klebsiella pneumoniae / Q000187:drug effects / Q000302:isolation & purification; D008137:Longitudinal Studies; D011550:Pseudomonas aeruginosa / Q000187:drug effects / Q000302:isolation & purification; D012189:Retrospective Studies; D015662:Trimethoprim, Sulfamethoxazole Drug Combination / Q000494:pharmacology / Q000627:therapeutic use
chemical_list: D000900:Anti-Bacterial Agents; D002939:Ciprofloxacin; D015662:Trimethoprim, Sulfamethoxazole Drug Combination