Abstract
Purpose: :
To test the clinical efficacy of the old antibiotics versus new fourth generation fluoroquinolones against Staphylococcus aureus keratitis in rabbits.
Methods: :
New Zealand white rabbits (24 rabbits, 48 eyes) were divided into four treatment groups (12 eyes/group): 1, gentamycin (14 mg/ml) and vancomycin (50 mg/ml); 2, gatifloxacin (0.3%); 3, moxifloxacin (0.5%); and 4 (control group), balanced salt solution (BSS). The eyes were topically treated every 30 minutes from 20 hours post S. aureus infection with one drop of the ophthalmic antibiotic solutions or one drop of BSS. Keratitis was clinically evaluated in all groups. One hour after the last dose, all rabbits were sacrificed, and corneal buttons were harvested using a disposable 9.5–mm diameter trephine. The excised corneas were homogenized for bacterial colony counts.
Results: :
Treatment of the infected corneas with either gentamycin plus vancomycin, gatifloxacin, or moxifloxacin reduced the number of viable S. aureus organisms by approximately 2 log colony–forming units (CFU)/cornea, 1 log CFU/cornea, and 1 log CFU/cornea, respectively, compared to the untreated control group (P<0.0001). Group 3 eyes showed a greater decrease in the number of viable bacteria postinfection compared to group 2 eyes, namely, 12.6 x 107 vs. 15.8 x107 CFU/cornea, respectively (P<0.0001).
Conclusions: :
Treatment with older antibiotics, i.e., gentamycin and vancomycin, was more effective than the new fourth–generation fluoroquinolones, i.e., gatifloxacin or moxifloxacin in the treatment of S. aureus keratitis in rabbits.
Keywords: keratitis • Staphylococcus • cornea: basic science