Fungal Identification By A New Slide Culture And In Vitro Drug Susceptibility Using Etest In Fungal Keratitis

Purpose: To investigate the spectrum of fungal species causing keratitis and to test anti-fungal drug susceptibility to each isolate using Etest. Subjects and methods: Microbial cultures were performed for patients who were clinically diagnosed as fungal keratitis between September 2002 and March 2006. A new slide culture was established to identify the fungal species of the isolates. Etest (AB BIODISK, Solna, Sweden) was applied to determine the antifungal agent susceptibility of each isolate to itraconazole, fluconazole and amphotericin B in vitro, respectively.Results: Among 216 eyes of 216 patients with clinical diagnosis of fungal keratitis, 165 strains of fungi were isolated from 164 eyes. The rate of positive-culture was 76.4% of the all cases. The spectrum of fungal species involved: 160(97.0%) isolates of filamentous fungi, including the two most common genera of Fusarium (n=77, 46.7%) and Aspergillus (n=23, 13.9%), followed by 60 (36.4%) isolates of other genera of filamentous fungi such as Acremonium (n=12, 7.3%), Alternaria (n=8,4.8%), Curvularia(n=8,4.8%),Chrysosporium (n=5, 3.0%), Trichophyton (n=3, 1.8%), Colletotrichum(n=3, 1.8%), Ulocladium (n=2, 1.2%), Bipolaris (n=2, 1.2%), Exserohilum (n=l, 0.6%), Verticillium (n=1, 0.6% ), Scedosporium (n=1, 0.6% ). 3 (1.8%) yeast of Candida, as well as 2(1.2%) dimorphic fungi of Blastomyces and Sporothrix isolate each. Fourteen filamentous fungi of the isolates failed to be identified according to the information provided by slide culture. The result of Etest showed that 37 (48.1%) isolates of Fusarium were susceptible to amphotericin B, whereas 1(1.3%) of them was sensitive to itraconazole, and 2 (2.6%) of them were sensitive to fluconazole. All 23 (100%) isolates of Aspergillus were sensitive to itraconazole, whereas 9(39.1%) of them were sensitive to amphotericin B, and only 2 (8.7%) of them were sensitive to fluconazole. All 21(100%) isolates of Dematiaceae were sensitive to amphotericin B, whereas 18(85.7%) of them were sensitive to itraconazole, and 19 (90.5%) of them were sensitive to fluconazole. 9 (75%) isolates of Acremonium were susceptible to itraconazole and fluconazole, whereas 3(25%) of them was sensitive to amphotericin B. Accounting for 25 (78.1%), 19 (59.4%) and 12(37.5%) isolates of the remained 32 organisms were sensitive to amphotericin B, itraconazole and fluconazole, respectively. Conclusion: Fusarium Aspergillus Dematiaceae and Acremonium are the most frequent pathogenic organisms in causing fungal keratitis , whereas other species of fungi can also cause corneal infection. In vitro Etest for assessing anti-fungal drug susceptibility is a simple and practical method, may providereferential information for clinical consideration of choosing antifungal agents to treat fungal keratitis.