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In vitro antimicrobial activity of levofloxacin against Streptococcus pneumoniae
1Department of Internal Medicine, Taichung Veterans General Hospital, Taiwan, R.O.C.
Background:
Infections caused by Streptococcus pneumoniae continue to be a significant cause of mortality and morbidity in humans. Diseases caused by multi-resistant pneumococci are increasing rapidly worldwide. The fluoroquinolones have been widely used clinically to treat infectious diseases. The results of a study here on the five fluoroquinolones susceptibilities of S. pneumoniae are reported from the Taichung Veterans General Hospital.
Methods:
Minimum inhibitory concentrations (MICs) of five quinolones (enoxacin, norfloxacin, ofloxacin, levofloxacin and ciprofloxacin) were determined for 106 strains of S. pneumoniae. All MICs were determined by the agar dilution method utilizing Mueller-Hinton agar supplemented with 5% sheep blood.
Results:
MIC90 of levofloxacin was 1 microgram/ ml, and was unaffected by penicillin-susceptibility. MIC90 of ofloxacin and that of ciprofloxacin were 2 and 4 micrograms/ml, respectively, with 90.6% sensitive to ofloxacin. MIC90 of enoxacin and that of norfloxacin were higher than other compounds.
Conclusions:
The in vitro activity of levofloxacin is twice that of ofloxacin, 4-fold of ciprofloxacin, 16-fold of norfloxacin, and 64-fold of enoxacin. MICs of these five quinolones were unaffected by penicillin-susceptibility. The antibacterial activity of levofloxacin was better than that of ofloxacin and ciprofloxacin, norfloxacin, or enoxacin against S. pneumoniae.
Insights
Levofloxacin demonstrated superior in vitro activity against Streptococcus pneumoniae compared to other fluoroquinolones. This finding is crucial for treating infections caused by multi-resistant pneumococci.
Area of Science:
- Microbiology
- Infectious Diseases
- Pharmacology
Background:
- Streptococcus pneumoniae infections cause significant human mortality and morbidity.
- Increasing global prevalence of multi-drug resistant pneumococci necessitates effective treatment strategies.
- Fluoroquinolones are widely utilized antibiotics for bacterial infections.
Purpose of the Study:
- To evaluate the in vitro susceptibilities of five fluoroquinolones against clinical isolates of Streptococcus pneumoniae.
- To compare the efficacy of levofloxacin, ofloxacin, ciprofloxacin, norfloxacin, and enoxacin against S. pneumoniae.
Main Methods:
- Minimum inhibitory concentrations (MICs) for five quinolones were determined for 106 S. pneumoniae strains.
- Agar dilution method using Mueller-Hinton agar with 5% sheep blood was employed.
- Penicillin-susceptibility of strains was considered in the analysis.
Main Results:
- Levofloxacin exhibited the lowest MIC90 (1 microgram/ml), indicating potent activity.
- Ofloxacin and ciprofloxacin showed MIC90 values of 2 and 4 micrograms/ml, respectively.
- Enoxacin and norfloxacin displayed higher MIC90 values, suggesting reduced activity.
Conclusions:
- Levofloxacin demonstrated significantly greater in vitro antibacterial activity against S. pneumoniae compared to ofloxacin, ciprofloxacin, norfloxacin, and enoxacin.
- The observed fluoroquinolone susceptibilities were independent of the penicillin-susceptibility of the S. pneumoniae strains.
- Levofloxacin represents a promising therapeutic option for pneumococcal infections, particularly those caused by resistant strains.