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Methicillin-resistant Staphylococcus aureus keratitis in the rabbit: therapy with ciprofloxacin, vancomycin and
M C Callegan1, J M Hill, M S Insler
1Department of Microbiology, Louisiana State University Medical Center School of Medicine, New Orleans 70112.
Abstract:
To determine the efficacy of a fluoroquinolone antibiotic in the treatment of methicillin-resistant Staphylococcus aureus (MRSA) keratitis, topical administration of 0.3% ciprofloxacin was compared with topical 5.0% vancomycin or 5.0% cefazolin in experimental infections in the rabbit eye. The infections were established by intrastromal injection of 100 colony forming units (CFU) of MRSA, which resulted in greater than 10(6) CFU per cornea by 12 hr postinfection. Chemotherapy (one drop every 15 min) was given from 4-9, 10-15, or 10-20 hr postinfection. Early therapy (4-9 hr postinfection) with ciprofloxacin rendered all eyes free of bacteria; ciprofloxacin was significantly more effective than vancomycin or cefazolin. When treatment was initiated 6 hr later (10-15 hr postinfection), no corneas became free of bacteria, but ciprofloxacin was again more effective than vancomycin or cefazolin. Bacterial killing by ciprofloxacin after treatment from 10-20 hr postinfection was also significantly greater than that of vancomycin. Overall, the results show that ciprofloxacin is effective in killing methicillin-resistant staphylococcus aureus, and is most effective when applied during the very early stages of infection.
Insights
Ciprofloxacin effectively treats methicillin-resistant Staphylococcus aureus (MRSA) eye infections in rabbits. Early topical application of ciprofloxacin demonstrated superior efficacy compared to vancomycin or cefazolin in clearing MRSA keratitis.
Area of Science:
- Ophthalmology
- Infectious Diseases
- Pharmacology
Background:
- Methicillin-resistant Staphylococcus aureus (MRSA) is a significant cause of bacterial keratitis.
- Effective treatment options for MRSA keratitis are crucial to prevent vision loss.
Purpose of the Study:
- To evaluate the efficacy of topical ciprofloxacin in treating experimental MRSA keratitis.
- To compare ciprofloxacin's effectiveness against vancomycin and cefazolin.
Main Methods:
- Experimental MRSA keratitis was induced in rabbit eyes via intrastromal injection.
- Topical treatments (0.3% ciprofloxacin, 5.0% vancomycin, 5.0% cefazolin) were administered at different time points post-infection.
- Bacterial load in corneas was quantified to assess treatment efficacy.
Main Results:
- Early administration (4-9 hr postinfection) of ciprofloxacin eradicated MRSA in all treated eyes.
- Ciprofloxacin showed significantly greater efficacy than vancomycin or cefazolin, even when treatment was initiated later (10-15 hr postinfection).
- Bacterial killing was significantly higher with ciprofloxacin compared to vancomycin when treatment started at 10-20 hr postinfection.
Conclusions:
- Topical ciprofloxacin is highly effective against MRSA keratitis in a rabbit model.
- The efficacy of ciprofloxacin is time-dependent, with earlier application yielding better outcomes.
- Ciprofloxacin represents a promising therapeutic option for MRSA-related eye infections.