The Antimicrobial Preservative Efficacy of ZymarTM vs. VigamoxTM Against Isolates of Filamentous Fungi at Room Temperature

Abstract

Abstract: : Purpose: To compare the antimicrobial preservative efficacy of Zymar^TM (gatifloxacin ophthalmic solution 0.3%, preserved with 0.005% benzalkonium chloride; BAK) with that of Vigamox^TM (moxifloxacin ophthalmic solution 0.5%, not preserved) at room temperature against a variety of filamentous fungi in vitro. Methods:Alternaria alternata (1 strain), Aspergillus fumigatus (1), Aspergillus niger (1), Cladophialophora carrionii (1), Cladosporium cladosporoiides (1), Fusarium solani (3), Penicillium chrysogenum (1), Penicillium citrinum (1), Scopulariopsis brevicaulis (1), and Trichosporon cutaneum (1) were grown on Potato dextrose agar for 1 week at room temperature. The fungal spores of each isolate were washed from the media with saline Tween and each suspension filtered to remove mycelia. Equal aliquots of commercially available Zymar^TM and Vigamox^TM were inoculated to contain approximately 1x10⁵ to 1x10⁶ colony forming units (CFU) of each test organism per mL of test solution. The numbers of viable CFUs per mL of test solution were determined at 24 and 48 hours, and 7, 14, and 28 days. Results: Vigamox^TM allowed more fungal recovery than did Zymar^TM for all 12 fungal strains at all time points through day 7. In all 12 fungal strains, Zymar^TM solution produced reductions in growth after 24 and 48 hours that were at least 2–log (99%) greater than those produced by Vigamox^TM. A total of 8 strains treated with Vigamox^TM were shown to remain at levels of at least 10⁵ CFU/mL at 24 hours while 8 strains treated with Zymar^TM were reduced to levels of no recovery. By 28 days, all of the strains treated with Zymar^TM were reduced to levels of no recovery, while 5 strains treated with Vigamox^TM remained at levels of at least 3 x 10² CFU/mL. Conclusions: Zymar^TM preserved with 0.005% BAK kills all strains of filamentous fungi tested at room temperature to a greater extent than does unpreserved Vigamox^TM. This antifungal benefit carries the potential for preventing ocular infection caused by fungal contamination of the bottle of ophthalmic solution during patient use.

Keywords: antibiotics/antifungals/antiparasitics