Comparative efficacy of topical gatifloxacin with ciprofloxacin, amikacin, and clarithromycin in the treatment of experimental Mycobacterium chelonae keratitis

Objective: To determine the comparative efficacy of topical gatifloxacin with ciprofloxacin, fortified amikacin, and clarithromycin against Mycobacterium chelonae keratitis in an animal model. Methods: Experimental M chelonae keratitis was induced via intrastromal inoculation in a rabbit model. Thirty-five rabbits were randomly divided into 5 groups and each group was treated hourly for 12 hours with topical 0.9% balanced salt solution, 0.3% gatifloxacin, 0.3% ciprofloxacin hydrochloride, a combination of topical fortified amikacin sulfate (50 mg/mL) and clarithromycin (10 mg/mL), or a triple combination of topical 0.3% gatifloxacin, fortified amikacin sulfate (50 mg/mL), and clarithromycin (10 mg/mL). Antibacterial efficacy of each regimen was determined by quantitative bacteriologic analysis. Results: Treatment with 0.3% gatifloxacin or the triple combination of 0.3% gatifloxacin, topical fortified amikacin sulfate (50 mg/mL), and clarithromycin (10 mg/mL) reduced the number of mycobacterial organisms more significantly than the controls that were treated with a topical balanced salt solution (both P < .001). Therapy with 0.3% gatifloxacin was more effective than 0.3% ciprofloxacin alone (P < .001) and demonstrated synergy by enhancing the efficacy of the combination of fortified amikacin (50 mg/mL) and clarithromycin (10 mg/mL) (P < .001). Neither 0.3% ciprofloxacin nor the combination of fortified amikacin (50 mg/mL) and clarithromycin (10 mg/mL) demonstrated a significant difference in activity against mycobacteria compared with the topical balanced salt solution. Conclusion: These results suggest that topical 0.3% gatifloxacin ophthalmic solution can be a new initial treatment agent against M chelonae keratitis. Clinical Relevance: Topical gatifloxacin 0.3% may provide an initial alternative in thereapy of M chelonae keratitis.