title: Comparative activities of cefepime and piperacillin/tazobactam tested against a global collection of Escherichia coli and Klebsiella spp. with an ESBL phenotype.
abstract: Cefepime exhibits more stability to hydrolysis by extended-spectrum beta-lactamases (ESBLs) compared with other cephalosporins, and piperacillin/tazobactam may be active against these pathogens because of the enzyme inhibitory activity of tazobactam. Thus, we evaluated the in vitro activity of these 2 antimicrobials against a large collection of isolates with an ESBL phenotype. A total of 50,637 clinical isolates (34,367 Escherichia coli and 16,270 Klebsiella spp.) collected from more than 80 medical centers (1998-2004) were tested by reference broth microdilution methods, and isolates with an ESBL phenotype (MIC, > or = 2 microg/mL for aztreonam or ceftazidime or ceftriaxone) were submitted to a clavulanate inhibition test (confirmation of ESBL production). Among isolates from North America, 3.9% of E. coli and 8.6% of Klebsiella spp. showed an ESBL phenotype, whereas among isolates from the rest of the world (ROW) (Europe, Latin America, and Asia), 7.7% of E. coli and 28.3% of Klebsiella spp. exhibited this pattern. Confirmation rates varied from 21.6% of E. coli in North America to 52.8% of Klebsiella spp. in the row Among E. coli from North America, cefepime (90.3% susceptibility) was generally more active than piperacillin/tazobactam (82.7%), especially among ESBL-not-confirmed (97.0% versus 85.5%). Cefepime also showed reasonable activity against Klebsiella spp. from North America (89.4% susceptibility). In general, isolates from North America exhibited higher susceptibility rates to both beta-lactams compared with isolates from the ROW, and ESBL-not-confirmed strains showed generally higher susceptibility rates than ESBL-confirmed organisms.
authors.affiliation: JMI Laboratories, North Liberty, IA 52317, USA. helio-sader@jmilabs.com
authors.forename: Helio S
authors.initials: HS
authors.lastname: Sader
authors.forename: Andre
authors.initials: A
authors.lastname: Hsiung
authors.forename: Thomas R
authors.initials: TR
authors.lastname: Fritsche
authors.forename: Ronald N
authors.initials: RN
authors.lastname: Jones
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D000077723:Cefepime; D002511:Cephalosporins / Q000494:pharmacology*; D024901:Drug Resistance, Multiple, Bacterial / Q000187:drug effects; D004926:Escherichia coli / Q000187:drug effects*; D006801:Humans; D007709:Klebsiella / Q000187:drug effects*; D008826:Microbial Sensitivity Tests / Q000379:methods*; D010397:Penicillanic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D010878:Piperacillin / Q000494:pharmacology; D000077725:Piperacillin, Tazobactam Drug Combination; D001618:beta-Lactamases / Q000187:drug effects
chemical_list: D000900:Anti-Bacterial Agents; D002511:Cephalosporins; D000077725:Piperacillin, Tazobactam Drug Combination; D000077723:Cefepime; D010397:Penicillanic Acid; D001618:beta-Lactamases; D010878:Piperacillin