title: Cross-Canada survey of resistance of 2747 aerobic blood culture isolates to piperacillin/tazobactam and other antibiotics.
abstract: OBJECTIVE
  To compare the activity of piperacillin/tazobactam with that of other broad parenteral antibiotics against aerobic and facultative anaerobic blood culture isolates in a Canada-wide survey.
  
  
  METHODS
  Fifty-eight laboratories in nine provinces each contributed up to 50 consecutive clinically significant aerobic and facultative anaerobic isolates for susceptibility testing.
  
  
  METHODS
  Participating hospitals included both tertiary care and community hospitals.
  
  
  METHODS
  Testing was performed in five regional centres by using the same microbroth dilution method, and results were interpreted according to National Commitee for Clinical Laboratory Standards M7-A3 and M100-S5 guidelines.
  
  
  RESULTS
  Piperacillin/tazobactam and imipenem were both active against more than 99% of the 1616 strains of Enterobacteriaceae species tested. The minimum inhibitory concentration of 90% of isolates (MIC(90)) of all Enterobacteriaceae species was 2 mg/L for piperacillin/tazobactam compared with 64 mg/L for piperacillin alone. Seventeen per cent of strains of Enterobacteriaceae species were susceptible to piperacillin/tazobactam but resistant to piperacillin. Piperacillin/tazobactam was highly active against Pseudomonas aeruginosa, inhibiting 99.1% of strains. MIC(90) was 8 mg/L. Nine per cent of P aeruginosa strains were not susceptible to imipenem. Most of these strains had a MIC of 8 mg/L, which falls in the intermediate category. Ninety-seven per cent of P aeruginosa were susceptible to ciprofloxacin and 97.3% to tobramycin. Ninety-six per cent of strains of Actinobacter species were susceptible to piperacillin/tazobactam, whereas only 76% of strains were susceptible to piperacillin alone. Overall, piperacillin/tazobactam was the most active agent tested; 98% of all strains were susceptible, followed closely by imipenem, to which 97.8% of strains were susceptible.
  
  
  CONCLUSIONS
  Aerobic blood culture isolates from Canadian centres continue to be highly susceptible to a variety of antibiotics. The broad spectrum of activity of piperacillin/tazobactam suggests that this combination should be considered for empirical treatment of sepsis while awaiting results of cultures and susceptibility testing.
authors.affiliation: Division of Microbiology, Department of Pathology and Laboratory Medicine, Queen Elizabeth II Health Sciences Centre, Halifax, Nova Scotia; Department of Microbiology and Infectious Diseases, Hôpital Maisoneuve-Rosemont, Montréal, Québec; Microbiology and Public Health, University of Alberta Hospital, Edmonton, Alberta; Wyeth-Ayerst Canada Inc; Department of Microbiology, Mount Sinai & Princess Margaret Hospitals; Department of Microbiology, Sunnybrook Health Science Centre, Toronto, Ontario.
authors.forename: K R
authors.initials: KR
authors.lastname: Forward
authors.forename: P A
authors.initials: PA
authors.lastname: Franks
authors.forename: D E
authors.initials: DE
authors.lastname: Low
authors.forename: R
authors.initials: R
authors.lastname: Rennie
authors.forename: A E
authors.initials: AE
authors.lastname: Simor