title: In vitro activity of piperacillin/tazobactam and ertapenem against Bacteroides fragilis and Escherichia coli in pure and mixed cultures.
abstract: Ertapenem and piperacillin/tazobactam are beta-lactam antibiotics with a broad spectrum of activity used for the treatment of mixed infections in which Bacteroides fragilis and Escherichia coli play an important aetiological role. In this study, the activities of piperacillin/tazobactam and ertapenem (MIC and time-kill kinetics) against these bacteria were compared. MICs were determined by the agar dilution method, and the time and slope of time-kill curves were analysed. In the in vitro pharmacodynamic assays, pure and mixed cultures of E. coli and B. fragilis were exposed to peak concentrations of ertapenem (8.0 microg ml(-1)) and piperacillin/tazobactam (64.0/8.0 microg ml(-1)) for 48 h. Treatment with ertapenem reduced the viability of E. coli and/or B. fragilis by 3 logs in all experiments, whereas piperacillin/tazobactam only affected the viability of B. fragilis. Both drugs exhibited their fastest rates of killing when bacteria were grown in mixed cultures. According to the results, ertapenem exhibited activity similar to that of piperacillin/tazobactam against B. fragilis alone or in mixed culture. However, ertapenem exhibited a markedly higher activity against E. coli alone or in combination with B. fragilis relative to piperacillin/tazobactam.
authors.affiliation: Departamento de Microbiologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil.
authors.forename: Kênia
authors.initials: K
authors.lastname: Valéria Dos Santos
authors.affiliation: Departamento de Microbiologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil.
authors.forename: Cláudio Galuppo
authors.initials: CG
authors.lastname: Diniz
authors.affiliation: Departamento de Microbiologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil.
authors.forename: Simone Cristina
authors.initials: SC
authors.lastname: Coutinho
authors.affiliation: Departamento de Microbiologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil.
authors.forename: Ana Carolina Morais
authors.initials: ACM
authors.lastname: Apolônio
authors.affiliation: Departamento de Microbiologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil.
authors.forename: Luciana
authors.initials: L
authors.lastname: Geralda de Sousa-Gaia
authors.affiliation: Departamento de Microbiologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil.
authors.forename: Jacques Robert
authors.initials: JR
authors.lastname: Nicoli
authors.affiliation: Departamento de Microbiologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil.
authors.forename: Luiz de Macêdo
authors.initials: LM
authors.lastname: Farias
authors.affiliation: Departamento de Microbiologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil.
authors.forename: Maria Auxiliadora
authors.initials: MA
authors.lastname: Roque de Carvalho
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001441:Bacteroides fragilis / Q000187:drug effects*; D015169:Colony Count, Microbial; D000077727:Ertapenem; D004926:Escherichia coli / Q000187:drug effects*; D008826:Microbial Sensitivity Tests; D050296:Microbial Viability; D010397:Penicillanic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D010878:Piperacillin / Q000494:pharmacology; D000077725:Piperacillin, Tazobactam Drug Combination; D013997:Time Factors; D047090:beta-Lactams / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D047090:beta-Lactams; D000077725:Piperacillin, Tazobactam Drug Combination; D010397:Penicillanic Acid; D000077727:Ertapenem; D010878:Piperacillin