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Comparative in vitro activity of piperacillinl tazobactam against Gramnegative bacilli


Lynne D. Liebowitz
Keith P. Klugman

Abstract

Objective. To describe the in vitro activity of piperacillinl tazobactam against clinical isolates of Gram-negative bacteria, compared with other antibacterial agents.
Design. Survey of susceptibility of clinical isolates of Gram-negative bacilli.
Setting. Academic hospitals of the University of the Witwatersrand teaching complex. Bacterial strains_ 180 selected clinical isolates of Gramnegative bacilli.
Main outcome measures. Minimum inhibitory concentrations (MICs) determined by agar dilution using techniques according to the recommendations of the National Committee for Clinical Laboratory Standards.
Results. Ciprofloxacin, biapenem, imipenem, cefepime and cefpirome were all highly active against most of the Enterobacteriaceae. All the ampicillin-resistant strains of Enterobacteriaceae were susceptible to piperacillinl tazobactam, MICSll values being 4/4 mgll for Klebsiella and Proteus/Providencia spp., 8/4 mg/l for Citrobacter and Serratia spp_, and 16/4 mg/l for Escherichia coli. All the agents, with the exception of ampicillin (MIC90 4 mg/l) and chloramphenicol (MIC90 4 mg/l), were highly active against the Haemophilus influenzae isolates tested. All Bacteroides fragilis strains were susceptible to piperacillinllazobaclam (MIC90 8/4 mgll), as well as 10 co-amoxiclav (MIC90 4/2 mg/I), biapenem and imipenem (MIC90 0.5 mg/l). The Pseudomonas spp. lested included strains resistant to piperacillinltazobactam, ceftazidime, biapenem, gentamicin, tobramycin and ciprofloxacin. Cefepime was the most active agent against Pseudomonas isolates, with 90% of the strains being susceptible to this agent, while biapenem was the mast active agent against the Acinetobacter isolates investigated.
Conclusions. The in vitro spectrum of activity of piperacillin!tazobactam against the majority of isolates was comparable to those of the other new agents tested.


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eISSN: 2078-5135
print ISSN: 0256-9574