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Postantibiotic effect of ciprofloxacin compared with that of five other quinolones
F Minguez1, C Ramos, S Barrientos
1Department of Microbiology, Faculty of Medicine, Complutense University, Madrid, Spain.
Abstract:
The antimicrobial activity (minimal inhibitory concentration, MIC, and killing kinetics) and postantibiotic effect (PAE) of different concentrations (MIC and 6 mg/1) of ciprofloxacin, norfloxacin, ofloxacin, pefloxacin, fleroxacin and lomefloxacin on pure cultures of Staphylococcus aureus and Escherichia coli were compared in vitro. The MIC, killing kinetics and PAE were determined by standard methods. Ciprofloxacin displayed the lowest MICs, while the highest were those of norfloxacin against S. aureus and lomefloxacin against E. coli. The killing curves showed ciprofloxacin to be the most and norfloxacin the least active. The bactericidal power was dependent on the concentration. At MIC, the fluoroquinolones, with the exception of norfloxacin, induced PAEs of 1-2 h. The effect was, in all cases, greater against E. coli. When assayed at 6 mg/l the PAEs were increased to 2-5 h, the best results being obtained by ciprofloxacin followed by ofloxacin. Norfloxacin produced no PAE on S. aureus and scarcely reached 1.3 h against E. coli. There was a close relationship between bactericidal power and PAE.
Insights
Ciprofloxacin demonstrated superior antimicrobial activity against Staphylococcus aureus and Escherichia coli, showing lower minimal inhibitory concentrations (MICs) and stronger bactericidal effects. Higher concentrations of fluoroquinolones generally increased the postantibiotic effect (PAE).
Area of Science:
- Microbiology
- Pharmacology
Background:
- Fluoroquinolones are broad-spectrum antibiotics.
- Understanding their comparative efficacy is crucial for clinical application.
Purpose of the Study:
- To compare the in vitro antimicrobial activity and postantibiotic effect (PAE) of various fluoroquinolones.
- To evaluate these effects on Staphylococcus aureus and Escherichia coli.
Main Methods:
- Determined minimal inhibitory concentration (MIC), killing kinetics, and PAE for ciprofloxacin, norfloxacin, ofloxacin, pefloxacin, fleroxacin, and lomefloxacin.
- Tested against pure cultures of S. aureus and E. coli at MIC and 6 mg/L concentrations.
Main Results:
- Ciprofloxacin exhibited the lowest MICs and most potent killing activity.
- Higher concentrations (6 mg/L) generally enhanced PAE, with ciprofloxacin and ofloxacin showing the best results.
- Norfloxacin displayed the least activity and minimal PAE, especially against S. aureus.
Conclusions:
- Ciprofloxacin is a highly effective fluoroquinolone against S. aureus and E. coli in vitro.
- Bactericidal power and PAE are concentration-dependent and closely related.
- Significant differences exist in the antimicrobial profiles of tested fluoroquinolones.