Topical fluoroquinolones: Antimicrobial activity and in vitro corneal epithelial toxicity

Abstract

To assess the potential of fluoroquinolones as topical antimicrobial agents, we evaluated in vitro the antimicrobial activity of five fluoroquinolones (ciprofloxacin, norfloxacin, ofloxacin, pefloxacin, and temafloxacin), as well as genta-micin, tobramycin, and cefazolin against 96 isolates of common bacterial corneal pathogens. Ciprofloxacin and temafloxacin were the most active quinolones [minimal inhibitory concentration inhibiting 90% of stains (MIC90) of 1 ug/ml], followed by ofloxacin (MIC90 2 ug/ml), and norfloxacin and pefloxacin (MIC90s 4 ug/ml). In contrast, gentamicin and tobramycin MlCggs were 32 and 64 ug/ml, respectively; cefazolin MIC90 was >2040 ug/ ml. The corneal epithelial cytotoxicity of the fluoroquinolones also was evaluated utilizing an in vitro assay of 3H-thymidine uptake of rabbit corneal epithelial cell cultures. The least to greatest toxicity of the fluoroquinolones were as follows: ciprofloxacin and temafloxacin < norfloxacin < ofloxacin < pefloxacin. Our study suggests that the fluoroquinolones, especially ciprofloxacin and temafloxacin, possess excellent in vitro activity against common bacterial corneal pathogens and are less toxic to the corneal epithelium than the aminoglycosides.