Comparison of Antimicrobial Efficacy of Topical Antibiotics in Rabbit Keratitis Model with Ciprofl oxacin, Methicillin-Resistant Staphylococcus Aureus

ABSTRACT

To compare the antimicrobial efficacy of several antibiotics in the treatment of ciprofloxacin and methicillin-resistant staphylococcus aureus(MCRSA)keratitis, we established a rabbit keratitis model by using MCRSA isolated from keratitis patient. A strain of MCRSA, approroximately 100 colony forming units in 10 microliterof phosphate buffered saline was injected intrastromally into the each cornea of New Zealand white rabbits. 30 rabbtits(30 eyes)were randomly divided into 5 groups and treated with either 0.3%ciprofloxacin, 0.3%trovafloxacin, 5%vancomycin, 5%cefazolin, or sterile deionized water.Topical antibiotics were administered every 15 min for 6 hours(750microliter). Rabbits were sacrified 1hour after the last eyedrop, and excised corneas were homogenized, diluted, and plated on BAP medium.Bacterial colonyforming units per cornea were quantified after 48-hour incubation. Aqueous humor were collected from each eye and drug concentration was counted with HPLC. The log1 0 value of colony forming units(CFUs)of vancomycin treated group was 4.85+/-0.64;ciprofloxacin, 6.16+/-0.46;trovafloxacin, 6.58+/-0.29;cefazolin, 6.25+/-0.25;and sterile deionized water, 6.57+/-0.33.In view of mean CFU, vancomycin showed greater antimicrobial activity and it was statistically significant(p<0.05). However, all of these treatment did not completely sterilize any corneas with 6-hour treatment. From these results, only topical vancomycin(5%)represented effective antimicrobial activity with short-term treatment in rabbit keratitis with MCRSA.