Evaluation of antifungal susceptibility and clinical characteristics in fungal keratitis in a tertiary care center in North India

Purpose: To study the antifungal susceptibility of common corneal pathogenic fungi to antifungal agents in the North Indian population. Methods: Prospective study of the antifungal sensitivity testing (natamycin, amphotericin B, voriconazole, itraconazole, fluconazole, posaconazole, caspofungin, micafungin) of fungal isolates from 50 cases of culture positive fungal keratitis by using E test method. Details noted included demographic data, visual acuity, clinical details, grade of keratitis, healing time, and success in medical management. Results: Of 50 patients with fungal keratitis (mean age: 40.28 +/- 16.77 years), 12 eyes healed within 3 weeks, 14 had a delayed healing response, and 24 had chronic keratitis. Among the 15 cases of Fusarium isolates, 93.3% were sensitive to natamycin, while 40% to amphotericin B; 66.6% to voriconazole, 13.4% to itraconazole and fluconazole each. 80% of Fusarium cases (n = 12) showed susceptibility to posaconazole. Among Aspergillus flavus isolates, 53.4% (n = 8) were sensitive to natamycin, with only 40% (n = 7) showing sensitivity to amphotericin B and good susceptibility to azoles. MIC against susceptible Fusarium spp. for natamycin was 3-16 mu g/mL, amphotericin B: 1-8 mu g/mL, voriconazole: 0.5-1.5 mu g/mL, itraconazole: 0.5-12 mu g/mL, posaconazole: 0.094-1.5 mu g/mL. MIC against Aspergillus flavus was natamycin: 8-32 mu g/mL, amphotericin B: 0.5-16 mu g/mL, voriconazole: 0.025-4 mu g/mL, itraconazole: 0.125-8 mu g/mL, posaconazole: 0.047-0.25 mu g/mL; against Aspergillus niger isolates, to natamycin was 6 mu g/mL (n=1), amphotericin B 8-12 mu g/mL (n = 3), voriconazole: 0.125-0.19 mu g/mL (n = 3), itraconazole: 0.38-0.75 mu g/mL, posaconazole: 0.064-0.19 mu g/mL and against Aspergillus fumigatus (n = 1), was natamycin4 mu g/mL, amphotericin B - 8 mu g/mL, voriconazole 0.25 mu g/mL, itraconazole 1 mu g/mL, and posaconazole 0.19 mu g/mL. MIC against susceptible Acremonium spp. for natamycin was 1.5-16 mu g/mL, amphotericin B: 0.5-8 mu g/mL, voriconazole: 0.19-3 mu g/mL, itraconazole: 0.125 mu g/mL, posaconazole: 0.125-0.5 mu g/mL and against susceptible Curvularia was natamycin 0.75-4 mu g/mL, amphotericin B 0.5-1 mu g/mL, voriconazole 0.125-0.19 mu g/mL, itraconazole 0.047-0.094 mu g/mL, posaconazole 0.047-0.094 mu g/mL. MIC against Mucor spp.+ Rhizopus spp. (n = 1) was natamycin: 8 mu g/mL, amphotericin B: 0.75 mu g/mL, posaconazole: 1.5 mu g/mL. MIC against of Alternaria (n = 1) was voriconazole: 0.19 mu g/mL, posaconazole: 0.094 mu g/mL. MIC against Penicillium (n=1) was natamycin: 8 mu g/mL, voriconazole: 0.25 mu g/mL, itraconazole: 0.5 mu g/mL, and Posaconazole: 0.125 mu g/mL. Conclusion: Our observations highlight the variations in susceptibility to antifungal agents. Posaconazole seems to be effective with low MIC against common corneal pathogenic fungal isolates.