TOPICAL CIPRROFLOXACIN VERSUS TOPICAL FORTIFIED ANTIBIOTICS IN RABBITMODELS OF STAPHYLOCOCCUS AND PSEUDOMONAS KERATITIS

We tested the antibacterial activity of ophthalmic 0.3% ciprofloxacin against that of 5.0% cefazolin and 1.36% tobramycin in two experimenta l models of keratitis, using a methicillin-sensitive strain of Staphyl ococcus aureus and an aminoglycoside-sensitive strain of Pseudomonas a eruginosa, respectively. Both corneas of New Zealand white rabbits wer e intrastromally injected with either S. aureus or P. aeruginosa. Twen ty-four hours later, each eye was topically treated hourly for 24 hour s. In the S. aureus model, the control group received Tears Naturale F ree (Alcon Laboratories, Inc., Fort Worth, TX), the ciprofloxacin grou p received 0.3%, ciprofloxacin and the cefazolin group received 5.0% c efazolin. In the P. aeruginosa model, the control group received Tears Naturale Free, the ciprofloxacin group received 0.3% ciprofloxacin, a nd the tobramycin group received 1.36% tobramycin. One hour after the last eyedrops were administered, the rabbits were killed, and their co rneas were processed for quantification of bacteria. For the S. aureus model, the mean (+/-SEM) colony forming units (CFU) of the control, 7 .1 x 10(6) (+/-4.0 x 10(6)); ciprofloxacin, 6.4 x 10(2) (+/-1.6 x 10(2 )) ; and cefazolin, 1.3 x 10(3) (+/-1.8 x 10(2)) groups were different (F = 17.5; p = 0.001). The ciprofloxacin and cefazolin groups were no t different from each other (p = 0.034). The mean (+/-SEM) CFU for the control group in the P. aeruginosa model was 2.8 x 10(8) (+/-1.7 x 10 (7)) . All corneas in the ciprofloxacin and tobramycin groups were ste rile. Short-term treatment with ciprofloxacin was an effective treatme nt when compared with both fortified cefazolin and fortified tobramyci n in eradicating S. aureus and P. aeruginosa, respectively, in these r abbit models of bacterial keratitis.