Povidone-iodine (betadine) in the treatment of experimental Pseudomonas aeruginosa keratitis

Topical 5% povidone-iodine for the treatment of corneal ulcers was observed in Sierra Leone, West Africa by one of us (D.J.D.). To test the efficacy of topical 5% povidone-iodine for infectious keratitis, experimental Pseudomonas aeruginosa keratitis was induced in 12 rabbits by first abrading the central 3 mm of corneal epithelium. Thirty milliliters of broth of P. aeruginosa strain ATCC 27835 (1.8 x 10⁷ viable bacteria) was dropped twice on the wounded cornea. After 22 h, all corneas were clinically infected. Eight rabbits were treated with 5% povidone-iodine solution and four with 0.9% NaCl solution. All were given hourly drops. Twenty-four hours after treatment began, the central 8-mm button of the infected cornea was excised, homogenized, and serial dilutions plated onto MacConkey agar. The total number of viable Pseudomonas organisms was calculated. The treatment group had 5.2±0.4 CFUs (colony-forming units) per cornea. The control group had 4.8±0.4 CFUs per cornea (p = 0.11). The clinical scores (Hobden grading system) were 6.9±1.5 for the treated group and 7.3±2.5 for the control group (p = 0.74). There was no statistical difference between the treated and control groups. Povidone-iodine (5%) is not effective in the acute treatment of P. aeruginosa keratitis in this rabbit model.