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Postantibiotic effect of imipenem on Pseudomonas aeruginosa
Abstract:
Imipenem (formerly N-formimidoyl thienamycin) and ceftazidime were investigated for their postantibiotic effect on Pseudomonas aeruginosa. Four strains of P. aeruginosa in the logarithmic phase of growth were exposed for 1 and 2 h to concentrations of antibiotics achievable in human serum. Recovery periods of test cultures were evaluated after dilution or addition of beta-lactamase. A consistent postantibiotic effect against all strains was obtained with imipenem but not with ceftazidime. Although ceftazidime did not have a postantibiotic effect, it did suppress the growth of the organisms at concentrations equivalent to one-third of the MIC. The clinical implications of these effects need further evaluation.
Insights
Imipenem demonstrated a consistent postantibiotic effect on Pseudomonas aeruginosa, while ceftazidime did not. However, ceftazidime suppressed bacterial growth at sub-inhibitory concentrations, warranting further clinical evaluation.
Area of Science:
- Microbiology
- Pharmacology
Background:
- Pseudomonas aeruginosa is an opportunistic pathogen.
- Understanding antibiotic postantibiotic effects (PAE) is crucial for optimizing treatment strategies.
Purpose of the Study:
- To investigate the postantibiotic effect of imipenem and ceftazidime on Pseudomonas aeruginosa.
- To compare the PAE of imipenem and ceftazidime against multiple strains of P. aeruginosa.
Main Methods:
- Exposure of four P. aeruginosa strains to imipenem and ceftazidime at clinically relevant concentrations for 1-2 hours.
- Evaluation of bacterial recovery after subculturing, with and without beta-lactamase addition.
Main Results:
- Imipenem consistently exhibited a postantibiotic effect against all tested P. aeruginosa strains.
- Ceftazidime did not produce a significant postantibiotic effect.
- Ceftazidime suppressed P. aeruginosa growth at concentrations as low as one-third of the minimum inhibitory concentration (MIC).
Conclusions:
- Imipenem possesses a notable postantibiotic effect against P. aeruginosa.
- Ceftazidime's lack of PAE but demonstrated growth suppression at sub-MIC levels requires further clinical investigation for therapeutic implications.