Influence of fluoroquinolone susceptibility on the therapeutic response of fluoroquinolone-treated bacterial keratitis

Abstract

Objective: To estimate how a corneal isolate's minimal inhibitory concentration for a fluoroquinolone agent affects the rate of clinical response of bacterial keratitis to fluoroquinolone therapy. Design: Prospective cohort study. Methods: Six hundred sixty-three individuals with suspected bacterial keratitis underwent diagnostic corneal scraping and were treated with topical 0.3% ciprofloxacin solution or ointment. Of 407 patients with culture-confirmed bacterial keratitis, improvement and cure rates with ciprofloxacin monotherapy were estimated for 391 who had in vitro ciprofloxacin susceptibility of the principal corneal isolate. Main Outcome Measures: Slitlamp biomicroscopic assessment for clinical improvement of corneal inflammation and for clinical cure with complete reepithelialization. Results: Adjusted rates of improvement and of cure were reduced, respectively, by 43% (95% confidence limits, 8%, 64%) and by 29% (95% confidence limits, 0%, 49%) among corneal infections having a ciprofloxacin minimal inhibitory concentration above 1.0 pg/mL compared with those with more sensitive isolates. Conclusions: Corneal infection by relatively ciprofloxacin-resistant bacteria responds more slowly to ciprofloxacin therapy. Antibacterial susceptibility testing of corneal cultures may predict the fluoroquinolone therapeutic response rate of bacterial keratitis.