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The in vitro and in vivo activity of ciprofloxacin
Abstract:
The antibacterial activity of ciprofloxacin (Bay o 9867) was compared with those of norfloxacin, nalidixic acid, trimethoprim-sulfamethoxazole, cefaclor, sisomicin and cefotaxime in in vitro and mouse protection studies. Approximately 300 clinical isolates of clinically important gram-positive and gram-negative species were used. The median MICs of ciprofloxacin against gram-positive and gram-negative bacteria ranged from less than or equal to 0.015-1 mg/l. Ciprofloxacin was 2-8 fold more active than norfloxacin and 100-fold more active than nalidixic acid. It also had a wider spectrum of activity against gram-positive organisms including even enterococci. No cross-resistance was observed between ciprofloxacin and beta-lactam antibiotics or aminoglycosides. Only acidic pH conditions decreased its activity. Ciprofloxacin showed rapid bactericidal action against organisms in both the logarithmic and stationary growth phases. In mouse protection studies (intraperitoneal infection) ciprofloxacin was significantly more effective than norfloxacin, ampicillin, trimethoprim-sulfamethoxazole, and also showed excellent activity against Pseudomonas infections.
Insights
Ciprofloxacin exhibits potent broad-spectrum antibacterial activity against Gram-positive and Gram-negative bacteria, outperforming other antibiotics in vitro and in vivo mouse protection studies. Its efficacy extends to resistant strains, with no cross-resistance observed with common antibiotic classes.
Area of Science:
- Microbiology
- Pharmacology
- Infectious Diseases
Background:
- Antibiotic resistance is a growing global health concern.
- Novel antibacterial agents with broad-spectrum activity are urgently needed.
- Fluoroquinolones represent a critical class of synthetic broad-spectrum antibiotics.
Purpose of the Study:
- To evaluate the antibacterial activity and efficacy of ciprofloxacin.
- To compare ciprofloxacin's performance against other key antibiotics.
- To assess ciprofloxacin's spectrum of activity and resistance patterns.
Main Methods:
- In vitro susceptibility testing (MIC determination) against ~300 clinical bacterial isolates.
- In vivo mouse protection studies using intraperitoneal infection models.
- Comparative analysis with norfloxacin, nalidixic acid, trimethoprim-sulfamethoxazole, cefaclor, sisomicin, and cefotaxime.
Main Results:
- Ciprofloxacin demonstrated potent activity against Gram-positive and Gram-negative bacteria, with MICs ≤0.015-1 mg/l.
- It was significantly more active than norfloxacin (2-8 fold) and nalidixic acid (100 fold).
- Ciprofloxacin showed broad-spectrum activity, including against enterococci, with no cross-resistance to beta-lactams or aminoglycosides; acidic pH reduced activity.
Conclusions:
- Ciprofloxacin possesses superior broad-spectrum antibacterial activity compared to other tested agents.
- Its rapid bactericidal action and efficacy in vivo highlight its potential as a key therapeutic agent.
- Ciprofloxacin offers a promising option for treating infections caused by a wide range of pathogens, including Pseudomonas.