title: Study of the comparative activity of piperacillin/tazobactam with currently available antibiotics against 8206 aerobic isolates.
abstract: OBJECTIVE
  To compare the activity of piperacillin-tazobactam with piperacillin and other parenterally administered antibiotics against aerobic Gram-negative bacilli and Gram-positive cocci isolated from across Canada, and to determine the prevalence of resistance mediated by extended-spectrum cephalosporinases.
  
  
  METHODS
  Sixty-one laboratories participated. Disk diffusion testing was performed in accordance with methods outlined by the National Committee for Clinical Laboratory Standards. Susceptibilities were performed on 8206 strains. Escherichia coli and Klebsiella pneumoniae with reduced susceptibilities to third-generation cephalosporins were screened for extended-spectrum beta-lactamases (ESBLs).
  
  
  RESULTS
  Piperacillin-tazobactam was active against 92% of the strains, piperacillin against 81% and ticarcillin-clavulanic acid against 88%. Few differences were observed in the relative susceptibility of strains from teaching or community hospitals, from different anatomic sites or from different regions of the country. Aerobic Gram-negative bacilli tested tended to be more susceptible to all the agents than was recently reported in a similar American study. Only 43% of Enterococcus faecium were susceptible to ampicillin and 42% to piperacillin piperacillin with and without tazobactam. Only two enterococcal strains were resistant to vancomycin, and 19 had intermediate zone sizes. Of the 10 strains of E coli and eight strains of K pneumoniae with reduced susceptibility to extended spectrum cephalosporins, only one demonstrated typical ESBL activity.
  
  
  CONCLUSIONS
  Canadian aerobic Gram-positive cocci and Gram-negative bacilli remain highly susceptible to many currently available antibiotics. The findings confirm a broad spectrum of activity of piperacillin-tazobactam and indicate that the pattern of susceptibility is quite uniform from different body sites, in both teaching and community hospitals, and across the country.
authors.affiliation: Division of Microbiology, Department of Pathology and Laboratory Medicine, Queen Elizabeth II Health Sciences Centre, Halifax, Nova Scotia. kforward@ac.dal.ca
authors.forename: K R
authors.initials: KR
authors.lastname: Forward
authors.forename: D E
authors.initials: DE
authors.lastname: Low
authors.forename: M
authors.initials: M
authors.lastname: Laverdiere
authors.forename: R
authors.initials: R
authors.lastname: Rennie
authors.forename: A E
authors.initials: AE
authors.lastname: Simor
authors.forename: P A
authors.initials: PA
authors.lastname: Franks