Efficacy and safety of gentamicin and streptomycin in Optisol-GS, a preservation medium for donor corneas.

Increasing reports of gentamicin-resistant bacteria contaminating donor corneas and causing endophthalmitis have indicated that preservation of corneal storage media with 100 micrograms/ml of gentamicin alone needs reevaluation. We investigated the stability and possible cytotoxicity of streptomycin as a supplement to gentamicin in Optisol corneal storage medium. The combination of gentamicin and streptomycin in Optisol solution was stable at room temperature for at least 4 weeks and inhibited the growth of Staphylococcus aureus, S. epidermidis, alpha hemolytic streptococci, Streptococcus Group D, Propionibacterium acnes, Escherichia coli, and diphtheroids, but not Pseudomonas aeruginosa. The addition of vancomycin did not significantly improve the antibacterial effectiveness of the gentamicin and streptomycin combination when stored at 4 degrees C. The growth of 15 of 20 clinical ocular isolates of Ps. aeruginosa was suppressed by the gentamicin-streptomycin combination. Streptomycin in concentrations of up to 1,000 micrograms/ml did not decrease the mitotic activity of corneal endothelial cells as evaluated by the in vitro incorporation of tritiated thymidine or cause cytotoxicity. The addition of 200 micrograms/ml of streptomycin to Optisol corneal storage medium containing 100 micrograms/ml of gentamicin may significantly improve activity against gentamicin-sensitive and gentamicin-resistant contaminants.