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Intravitreal vancomycin. Retinal toxicity, clearance, and interaction with gentamicin
Abstract:
Some of the gram-positive isolates from exogenous bacterial endophthalmitis cases treated at our institution have been found to be resistant to either cefazolin sodium, gentamicin sulfate, or both. However, all of these isolates have been sensitive to vancomycin. These findings prompted us to reevaluate the retinal toxicity and clearance of intravitreal vancomycin in pigmented rabbits. Doses up to 2 mg were found to be nontoxic in phakic and aphakic-vitrectomized eyes. Clearance was determined in phakic and aphakic-vitrectomized rabbit eyes with or without intact lens capsules. The antibiotic was cleared most slowly in phakic eyes. Aphakic-vitrectomized eyes without an intact lens capsule cleared antibiotic most rapidly, while aphakic-vitrectomized eyes with intact capsules exhibited an intermediate clearance rate. In addition, the interaction between vancomycin and gentamicin on gram-positive endophthalmitis isolates was found to be additive or synergistic depending on the bacterial species. Based on these data, we recommend the combination of vancomycin and an aminoglycoside as the initial antibiotic therapy for exogenous bacterial endophthalmitis.
Insights
Vancomycin is effective against resistant gram-positive bacteria causing endophthalmitis. Intravitreal vancomycin is safe in rabbits, with clearance rates varying by eye condition, supporting its use with aminoglycosides.
Area of Science:
- Ophthalmology
- Microbiology
- Pharmacology
Background:
- Gram-positive bacteria causing exogenous bacterial endophthalmitis exhibit resistance to cefazolin and gentamicin.
- Vancomycin demonstrates consistent sensitivity against these resistant isolates.
Purpose of the Study:
- To reevaluate the retinal toxicity of intravitreal vancomycin.
- To assess vancomycin clearance in rabbit eyes with varying surgical conditions.
- To investigate the synergistic effects of vancomycin and gentamicin.
Main Methods:
- Pigmented rabbits were used to test intravitreal vancomycin toxicity and clearance.
- Toxicity was assessed at doses up to 2 mg in phakic and aphakic-vitrectomized eyes.
- Clearance rates were measured in eyes with intact or absent lens capsules.
Main Results:
- Intravitreal vancomycin up to 2 mg was found to be non-toxic.
- Vancomycin clearance was slowest in phakic eyes and fastest in aphakic-vitrectomized eyes without intact lens capsules.
- Vancomycin and gentamicin demonstrated additive or synergistic interactions against bacterial isolates.
Conclusions:
- Intravitreal vancomycin is a safe and effective treatment option for bacterial endophthalmitis.
- Clearance kinetics are influenced by ocular anatomy, particularly the presence of the lens and vitreous.
- Combination therapy with vancomycin and an aminoglycoside is recommended for initial treatment of exogenous bacterial endophthalmitis.