The clinical and pathogenic characteristics of keratitis caused by Alternaria alternata

Abstract

To study the clinical and pathogenic characteristics of keratitis caused by Alternaria alternata and to provide evidence for the diagnose and treatment of mycotic keratitis. The patients with keratitis were examined by lamp microscope; the direct smears of corneal scrapings were stained using 10% potassium hydroxide and Giemsa's staining and the results were observed under microscope. After hypha was found, the samples from corneal were taken for fungal culture and fungal susceptibility test in vitro according to the National Community of Clinical Laboratory Standard (NCCLS) document M38-A at the same time. Ketoconazole, Amphotericin B and Fluconazole eye drops were applied into eyes frequently and alternately. The affectivity of the treatment were also observed. The isolates of Alternaria alternata from patients were used to induce keratitis in rabbits. The rabbits were sacrificed by air after 5 days and 14 days and their corneas were taken for pathology and inoculating for fungi. All the patients have only one eye with Alternaria alternata's keratitis and their average age was 50 years old. The lesions of corneal necrosis in the patients and Alternaria alternata's keratitis in the rabbits were appeared as light grey, shallow and a diffused edge. Alternaria alternata showed as thick transparent hypha and a great of spherical chlamydospores on the top of hypha or cluster one and the other in corneal scraping under microscope. The hypha and spores of Alternaria alternata in the culture medium were all brown and the spores were separated into cells like wall brick and grew on the top of spores linking like chains. Anti-microbial susceptibility testing in vitro showed that Alternaria alternata was susceptible to Voriconazole, Amphotericin B, Ketoconazole, Miconazole, Econazole, Terbinafine and Fluconazole but it was resistant to Clotrimazole, Flucytosine ang Itraconazole. 22 of the patients were cured by dropping Amphotericin B, Ketoconazole and Fluconazole frequently and alternately but surgery was performed in one case. The mean cured time was 34 day. The lesion of rabbits keratitis caused by Alternaria alternata was thin and localized only in the region of lacking epicytes. The isolate from the rabbit's keratitis model was Alternaria alternata. The keratitis caused by Alternaria alternata has its distinct clinical and laboratory characteristics. The virulence of Alternaria alternata is relatively low to cornea and the combination of anti-fungal agents could cure Alternaria alternata keratitis.