Abstract
Purpose::
To determine the efficacy of moxifloxacin in combination with voriconazole to inhibit Fusarium species.
Methods::
Ten Fusarium corneal isolates were obtained from The Methodist Hospital (Houston, TX). In vitro susceptibility testing with moxifloxacin (Vigamox®, Alcon, Fort Worth, TX) and voriconazole (VFEND®, Pfizer, New York, NY) alone and in combination was done by modified checkerboard microdilution. Fungi were freshly isolated from yeast-peptone-dextrose (YPD) plates, suspended in phosphate-buffered saline, and adjusted to a concentration of 104 colony-forming units (cfu)/mL using spectrophotometry. Each well of multiwell plates received 2 mL YPD, 5 µL of each Fusarium strain, and 50 µL antimicrobial drug(s). Serial tenfold dilutions of moxifloxacin (5.45 x 10-4 to 5.45 µg/mL) and fourfold dilutions of voriconazole (1.56 to 400 µg/mL) were tested alone and in various combinations. Plates were incubated with continuous shaking at 30°C and monitored for growth at 4 days.
Results::
No Fusarium strains grew in wells containing 400 µg/mL voriconazole. As the concentration of voriconazole decreased, fungal growth increased. For nine of ten Fusarium strains, addition of the moxifloxacin had no effect on fungi growth, but for one strain (F1100) moxifloxacin had an additive effect with voriconazole. For F1100, moxifloxacin concentrations higher than 5.45 x 10-3 mg/mL inhibited growth of this strain with or without voriconazole. At the lowest moxifloxacin concentration, no growth was observed with 400 µg/mL voriconazole and only slightly increased as the voriconazole concentration decreased.
Conclusions::
Moxifloxacin may occasionally potentiate the antifungal effect of voriconazole for some Fusarium strains. The use of empiric fluoroquinolone therapy for ulcerative keratitis may have a broad therapeutic role but could potentially hamper fungal recovery from corneal scrapings of keratomycosis.
Keywords: fungal disease • antibiotics/antifungals/antiparasitics