Effect of topical povidone-iodine versus topical ofloxacin on experimental Staphylococcus keratitis

To compare the antibacterial effect of povidone-iodine (PI) with that of ofloxacin in an experimental model of bacterial keratitis.

Staphyloccocal keratitis was induced in 21 eyes of Dutch Belted rabbits by intrastromal inoculation of approximately 280 organisms of Staphylococcus aureus. Six hours later, the animals were divided in four groups treated topically with saline 0.9%, Betadine 10%, Betadine 0.5% or Ofloxacin 0.3% (2 gtt every 30 min for 8 h). The central 8-mm cornea was excised, washed and homogenized. Colony counts were performed on serial 10-fold dilutions plated on blood and brain infusion agar and incubated overnight.

Colony-forming units per cornea were 7.4x10(7) for the saline group compared to 8.2x10(7) for PI 10% (P>0.5), 4.3x10(7) for PI 0.5% (P<0.01) and no organisms for ofloxacin 0.3%.

Betadine 0.5% demonstrates a statistically significant bactericidal effect compared with untreated staphyloccocal keratitis in our experimental model. Ofloxacin has superior antibacterial effect under the conditions studied. Further improvements in the povidone-iodine formulation are warranted prior to consideration for human keratitis.