In vitro susceptibilities of bacterial ocular isolates to fluoroquinolones

Abstract

Purpose: To evaluate and compare the in vitro antimicrobial activity of levofloxacin versus ciprofloxacin and ofloxacin against ocular isolates from patients with bacterial conjunctivitis.

Methods: The in vitro antimicrobial susceptibilities of ocular isolates to levofloxacin, ofloxacin, and ciprofloxacin were determined using both the agar disk diffusion and broth dilution methods.

Results: Disk diffusion susceptibility testing disclosed that 99% (100 of 101 isolates) of gram-negative isolates and 98% (127 of 129 isolates) of gram-positive isolates were susceptible to levofloxacin; 96% (97 of 101 isolates) of gram-negative isolates and 78% (100 of 129 isolates) of gram-positive isolates were susceptible to ofloxacin; and 94% (95 of 101 isolates) of gram-negative isolates and 61% (79 of 129 isolates) of gram-positive isolates were susceptible to ciprofloxacin. Broth dilution testing disclosed that 99% (72 of 73 isolates) of gram-negative isolates and 98% (111 of 113 isolates) of gram-positive isolates were susceptible to levofloxacin; 96% (70 of 73 isolates) of gram-negative isolates and 92% (104 of 113 isolates) of gram-positive isolates were susceptible to ofloxacin; and 95% (69 of 73 isolates) of gram-negative isolates and 82% (93 of 113 isolates) of gram-positive isolates were susceptible to ciprofloxacin.

Conclusions: In this study, levofloxacin demonstrated superior in vitro activity against human bacterial conjunctival isolates compared with either ofloxacin or ciprofloxacin (levofloxacin > ofloxacin > ciprofloxacin).