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Efficacy of ciprofloxacin and dexamethasone in experimental pseudomonas endophthalmitis
1Department of Ophthalmology, Kyungpook National University Hospital, Taegu, Korea.
Abstract:
To determine injection time and effective dose of ciprofloxacin in endophthalmitis and to evaluate the effectiveness of dexamethasone. In rabbits, Pseudomonas aeruginosa (2 x 10(4) CFU/0.1 ml) was inoculated intravitreally. At 6, 12, 18, 24 hours postinoculation, single intravitreal doses of ciprofloxacin (300 micrograms/0.15 ml or 100 micrograms/0.05 ml) alone or with dexamethasone (400 micrograms) were given. Electrophysiological and histologic measures were utilized to rate drug effectiveness. 300 micrograms ciprofloxacin was effective in killing P. aeruginosa at 6 and 12 hours postinoculation, but one hundred ug ciprofloxacin was not effective. 300 ug ciprofloxacin had no significant effect in killing P. aeruginosa at 18 hrs and 24 hrs postinoculation. Eyes treated with dexamethasone (400 micrograms) and ciprofloxacin (300 micrograms) at 6 hours postinoculation did not differ from eyes treated with ciprofloxacin alone. Cultures from eyes treated with dexamethasone and ciprofloxacin at 12 hours postinoculation were positive. Cultures from eyes treated with ciprofloxacin alone were negative. The failure of treatment at 18 hrs and 24 hrs postinoculation may be due to either an increased rate of clearance of drugs from the eyes or a reduced bactericidal effect of ciprofloxacin which could be altered by acidic pH, degree of hypoxia or bacterial counts. Dexamethasone had no beneficial effect in the treatment of P. aeruginosa endophthalmitis in the early phase.
Insights
The optimal dose of ciprofloxacin for treating Pseudomonas aeruginosa endophthalmitis in rabbits is 300 micrograms, effective up to 12 hours post-infection. Dexamethasone did not improve outcomes in this early-stage model.
Area of Science:
- Ophthalmology
- Microbiology
- Pharmacology
Background:
- Endophthalmitis is a severe intraocular infection.
- Early and effective treatment is crucial to preserve vision.
- Pseudomonas aeruginosa is a common causative agent of bacterial endophthalmitis.
Purpose of the Study:
- To determine the effective dose and optimal injection time for ciprofloxacin in treating Pseudomonas aeruginosa endophthalmitis.
- To evaluate the adjunctive role of dexamethasone in this model.
Main Methods:
- Intravitreal injection of Pseudomonas aeruginosa (2 x 10^4 CFU) into rabbit eyes.
- Administration of single intravitreal doses of ciprofloxacin (100 or 300 micrograms) alone or with dexamethasone (400 micrograms) at 6, 12, 18, or 24 hours post-inoculation.
- Assessment of treatment efficacy using electrophysiological and histological measures, and microbiological cultures.
Main Results:
- 300 micrograms of ciprofloxacin was effective against P. aeruginosa when administered at 6 and 12 hours post-inoculation.
- 100 micrograms of ciprofloxacin was ineffective at all tested time points.
- Ciprofloxacin at 300 micrograms showed no significant bactericidal effect at 18 and 24 hours post-inoculation.
- Co-administration with dexamethasone did not enhance the efficacy of ciprofloxacin at 6 hours.
- Microbiological cultures were positive when dexamethasone was used with ciprofloxacin at 12 hours, but negative with ciprofloxacin alone.
Conclusions:
- The effective dose of ciprofloxacin for early-stage Pseudomonas aeruginosa endophthalmitis in rabbits is 300 micrograms, with efficacy diminishing after 12 hours.
- Dexamethasone did not provide a beneficial effect and may have potentially negative impacts in this early phase of P. aeruginosa endophthalmitis.
- Factors such as drug clearance, altered bacterial susceptibility due to pH or hypoxia, and bacterial load may influence treatment failure at later time points.