Nano-Ag, relative to natamycin, exhibits potent in vitro activity against ocular pathogenic filamentous fungi.

As a disinfectant used in MPDSs, thimerosal showed the highest levels of antimicrobial activity against ocular pathogenic F. solani and A. flavus isolates. The concentrations of PHMB (0.0001%), cetylpyridinium chloride (0.00014%), and chlorhexidine (0.003%) in MPDSs are sublethal levels for ocular pathogenic F. solani and A. flavus isolates. Although multiple ingredients within MPDSs play a role in antimicrobial efficacy, antimicrobial activity may be significantly influenced by the disinfectants used in the solution formulations.

The in vitro activity of thimerosal versus those of amphotericin B and natamycin was assessed against 244 ocular fungal isolates. The activity of thimerosal against Fusarium spp., Aspergillus spp., and Alternaria alternata was 256 times, 512 times, and 128 times, respectively, greater than that of natamycin and 64 times, 32 times, and 32 times, respectively, greater than that of amphotericin B. Thimerosal's antifungal activity was significantly superior to those of amphotericin B and natamycin against ocular pathogenic fungi in vitro.The problem of keratomycosis in developing countries like China is more acute because of its higher incidence and the unavailability of effective antifungals (18,28,30). To date, only fluconazole and natamycin are commercially available for ocular use in China. Fluconazole has high bioavailability against Candida spp., but Fusarium spp. and Aspergillus spp. are resistant to it (3,27,29). Fusarium spp. and Aspergillus spp. are more commonly associated with keratomycosis, while Candida spp. are rarely implicated as etiological agents of keratomycosis in China (23,26). Natamycin is the only topical ophthalmic antifungal compound approved in the United States (14). Natamycin is poorly soluble in water. After topical application, natamycin penetrates the cornea and conjunctiva poorly and effective drug levels are not achieved in either the cornea or the aqueous humor (15); it is therefore useful only in the treatment of superficial keratomycosis. Due to the relative unavailability of effective antifungals, keratomycosis fails to resolve in many of the patients who receive antifungal treatment; some patients experience vision loss and eventually corneal perforation, ultimately require penetrating keratoplasty, or even enucleation or evisceration (20,28). Therefore, it is very important and urgent to explore broad-spectrum antifungals to effectively suppress a wide variety of ocular fungal pathogens and to develop new antifungal eye drops to combat this vision-threatening infection.Thimerosal is a preservative commonly used in ophthalmic solutions, otic drops, topical medicine, and vaccines because of its bactericidal property. However, the efficacy of thimerosal against ocular pathogenic fungi has not been evaluated so far. The present study was performed to determine the antifungal activity of thimerosal versus those of amphotericin B and natamycin against ocular pathogenic fungi in vitro. To our knowledge, this is the first study to determine the antifungal activity of thimerosal against main ocular pathogenic fungi. Results obtained in this study may contribute to the development of new antifungal eye drops.Two hundred forty-four strains of fungi isolated from patients with keratomycosis from the Henan Eye Institute in Zhengzhou, China, were investigated. These isolates were identified based on morphology by standard methods (22,23,25). They included 136 Fusarium isolates, 98 Aspergillus isolates, and 10 Alternaria alternata isolates. Candida parapsilosis ATCC 22019 was used as quality...