Comparison of antibiotic effect and corneal epithelial toxicity of levofloxacin and moxifloxacin in vitro.

PURPOSE

To compare the bacterial susceptibility and corneal epithelial toxicity of levofloxacin and moxifloxacin in the human corneal epithelial cells (HCECs).

METHODS

We used 2 types of strains, ie, American Type Culture Collection strains and resistant strains. The former included Staphylococcus aureus, coagulase-negative staphylococci, Pseudomonas aeruginosa, and Serratia marcescens, The latter were methicillin-resistant Staphylococcus aureus; methicillin-resistant, coagulase-negative Staphylococcus sp.; and ciprofloxacin-resistant P. aeruginosa. The HCECs were incubated with each bacterial population for 1 hour and exposed to both antibiotics for 1 hour. The colony-forming units of viable bacteria per well were expressed as base 10 logarithms. To determine corneal epithelial toxicity, we exposed the HCECs to each antibiotic agent, and the viable epithelial cells were quantified by the MTT assay. We also observed the wound healing rate of injured HCECs cultured in each antibiotic agent for 24 hours.

RESULTS

In bacterial susceptibility testing of antibiotics, levofloxacin was less effective for Serratia marcescens than moxifloxacin (P < 0.05). However, both moxifloxacin and levofloxacin showed the same efficacy against Gram-positive bacteria, P. aeruginosa, and resistant strains (P > 0.05). Moxifloxacin showed a higher toxicity than levofloxacin when the HCECs were exposed to the respective antibiotics for 2 and 24 hours (P < 0.05). The moxifloxacin inhibited the effect of wound healing in HCEC injury, but levofloxacin did not (P < 0.05).

CONCLUSIONS

There was no significant difference in antibiotic effects between moxifloxacin and levofloxacin on most bacterial strains, except for Serratia marcescens. On the other hand, levofloxacin seemed to be safer than moxifloxacin in HCECs.