In Vitro Antifungal Activity of the Fourth Generation Fluoroquinolones Against Candida Isolates from Human Ocular Infections

PURPOSE: To evaluate and compare the in vitro antifungal activity of moxifloxacin and gatifloxacin against Candida species isolated from ocular infections. METHODS: Tube microdilutions test was used to determine antifungal activity of the agents for 21 Candida isolates and one quality control strain. Drugs evaluated included topical preparations of fluoroquinolones (FQs), moxifloxacin (Vigamox), and gatifloxacin (Zymar). Serial dilutions of moxifloxacin (0.5%, 0.25%, 0.125%) and gatifloxacin (0.3%, 0.15%, 0.075%) were prepared for the microtube dilutions test. Aliquots (0.01 ul) were plated onto Sabouraud agar and colonies were counted. RESULTS: Both drugs undiluted inhibited greater than 95% of growth at 24 hrs. There was no significant difference between moxifloxacin and gatifloxacin at undiluted concentrations (p = 1.00); however, the mean number of colony forming units in gatifloxacin group was significantly less than that of moxifloxacin at diluted concentrations of the drugs (p < 0.05). CONCLUSIONS: Current commercial topical preparations of moxifloxacin and gatifloxacin demonstrated a definite in vitro antifungal activity against ocular Candida species; however, clinical efficacy of these agents remains unproven. The greater inhibition of growth of organisms with gatifloxacin compared to moxifloxacin is possibly because of the presence of BAK in Zymar.