title: Comparison of four antimicrobial susceptibility testing methods to determine the in vitro activities of piperacillin and piperacillin-tazobactam against clinical isolates of Enterobacteriaceae and Pseudomonas aeruginosa.
abstract: Susceptibility to piperacillin was similar to that to piperacillin-tazobactam (<1% difference) for 6,938 isolates of Enterobacter aerogenes and 13,954 isolates of Enterobacter cloacae tested using a Vitek system; for the same species, in contrast, susceptibility rates to piperacillin-tazobactam were 5.9 to 13.9% higher than to piperacillin using disk diffusion, MicroScan, and Vitek 2 testing. Unprecedented phenotypes (piperacillin susceptible and piperacillin-tazobactam intermediate; piperacillin intermediate and piperacillin-tazobactam resistant; piperacillin susceptible and piperacillin-tazobactam resistant) accounted for 6.1% of the results for E. aerogenes isolates and 6.0% of the results for E. cloacae isolates tested with the Vitek system.
authors.affiliation: Focus Technologies, Herndon, Virginia 20171, USA. jkarlowsky@focusanswers.com
authors.forename: James A
authors.initials: JA
authors.lastname: Karlowsky
authors.forename: Mellany K
authors.initials: MK
authors.lastname: Weaver
authors.forename: Clyde
authors.initials: C
authors.lastname: Thornsberry
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Dowzicky
authors.forename: Mark E
authors.initials: ME
authors.lastname: Jones
authors.forename: Daniel F
authors.initials: DF
authors.lastname: Sahm
mesh_terms: D024881:Drug Resistance, Bacterial; D004359:Drug Therapy, Combination / Q000494:pharmacology*; D004755:Enterobacteriaceae / Q000145:classification / Q000187:drug effects*; D006801:Humans; D008826:Microbial Sensitivity Tests / Q000379:methods; D010397:Penicillanic Acid / Q000031:analogs & derivatives / Q000494:pharmacology*; D010406:Penicillins / Q000494:pharmacology*; D010878:Piperacillin / Q000494:pharmacology*; D000077725:Piperacillin, Tazobactam Drug Combination; D011159:Population Surveillance; D011550:Pseudomonas aeruginosa / Q000187:drug effects*
chemical_list: D010406:Penicillins; D000077725:Piperacillin, Tazobactam Drug Combination; D010397:Penicillanic Acid; D010878:Piperacillin