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

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.

Bacteriologic Study on Conjunctiva of Eyeball Donor and Antibiotic Sensitivity Test

We evaluated the distribution of bacterial flora in conjunctiva of eyeball donor and antibiotic sensitivity of the cultured bacteria. Specimens were obtained from inferior conjunctiva cul de sac with sterile cotton-tipped applicator between 1-5 hours after death and plated on routine agar plates. Antibiotic sensitivity test was done by disk diffusion method. From 1994 to 1995, a total number of 338 specimens were collected from donor eyes. Among them, 191(56.5%) were culture positive and 147(43.5%) were culture negative. Among cultured 125 signle organisms, 86 organisms(68.8%) were Gram positive bacteria, 37(29.6%) Gram negative bacteria and 2(1.6%) fungi. Coagulase Negative Staphylococcus (CNS) (29.2%) and Pseudomonas aeruginosa (10.9%) were the most commonly isolated microorganisms. Antibiotic sensitivity test demonstrated a high rate of resistance in common pathogenic microorganisms such as CNS, Staphylococcus aureus and Pseudomonas aeruginosa. These microorganisms showed antibiotic resistance even to fluoroquinolone. Thus, aseptic enucleation and proper antibacterial treatment are prerequisite for the preparation of the donor cornea.