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.
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.
Karlowsky
James A
JA
Focus Technologies, Herndon, Virginia 20171, USA. jkarlowsky@focusanswers.com
Weaver
Mellany K
MK
Thornsberry
Clyde
C
Dowzicky
Michael J
MJ
Jones
Mark E
ME
Sahm
Daniel F
DF
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*
D010406:Penicillins; D000077725:Piperacillin, Tazobactam Drug Combination; D010397:Penicillanic Acid; D010878:Piperacillin