Continuous flow perfusion of gentamicin with a scleral shell reduces bacterial colony counts in experimental Pseudomonas keratitis.

Abstract

We have previously shown the pharmacokinetic value of delivering gentamicin to the rabbit anterior segment using the Morgan Therapeutic Lens. The present study utilized an intrastromal injection model of Pseudomonas keratitis to test the therapeutic efficacy of continuous flow delivery of gentamicin with the Morgan therapeutic lens. All eyes (n = 52) received an intrastromal injection of approximately 1800 colony forming units (CFU) of Pseudomonas aeruginosa. At 22 hours after injection, eyes were perfused for 6 hours with saline or gentamicin (1, 2.5 or 5 mg/ml), or received gentamicin drops (13.6 mg/ml) at 15 minutes for four doses, then hourly for 6 hours. Corneas were homogenized and plated to determine bacterial survival, and expressed as log colonies (CFU). Log CFU recovered were 7.37 +/- 0.04, 6.64 +/- 0.20, 5.64 +/- 0.31, and 3.56 +/- 0.50 log CFU for saline perfusion, 1, 2.5, 5 mg/ml gentamicin perfusion respectively. Following six hours of treatment with topical fortified gentamicin drops, 5.93 +/- 0.34 log CFU were recovered. Gentamicin perfusion (5 mg/ml) was significantly different from saline or the other treatment groups (P < 0.05). Continuous corneal perfusion with the Morgan Therapeutic Lens demonstrated an increasing dose response curve with increasing perfusate concentration. It was effective in the treatment of experimental Pseudomonas keratitis.