P083 Susceptibility pattern of fungal isolated from patients with otomycosis

Abstract Poster session 1, September 21, 2022, 12:30 PM - 1:30 PM Objectives Antifungal resistance is posing several new concerns to clinicians. Increased rates of azole and echinocandin resistance in various non-albicans Candida species and azole resistance in A. fumigatus may arise due to clinical or environmental exposure to these drugs. The study evaluated the antifungal susceptibility for clinical fungal isolates causing otomycosis. Methods A total of 89 Aspergillus isolates containing A. niger (58 isolates), A. flavus (19 isolates), A. fumigatus (12 isolates), and 25 Candida isolates containing C. parapsilosis (14 isolates), C. orthopsilosis (6 isolates), and C. albicans (5 isolates) collected from individuals with confirmed otomycosis during October 2020-November 2021 were tested for antifungal susceptibility testing (AFST). AFST of ketoconazole, voriconazole, tioconazole, amphotericin B, miconazole, fluconazole, nystatin, and itraconazole was conducted using the broth microdilution method based on CLSI (M38-A2, M27-A3) protocols. Conidia of molds and colonies of yeasts were harvested from fungal cultures on SDA incubated at 35°C; the turbidity of the suspension was then adjusted to OD630 nm = 80%-82%T for molds and 75%-77%T for yeasts. Results Mainly, all antifungals examined were effective against most Aspergillus isolates, aside from tioconazole (GM = 5.54767 μg/ml) and nystatin (GM = 2.10151 μg/ml). Terbinafine (GM = 1.69824 μg/ml) had minimal in vitro effects (Table 1). Nystatin (GM = 2.94853 μg/ml) and itraconazole (GM = 1.08673 μg/ml) showed higher GM MICs against all Candida species isolates. Conversely, amphotericin B (GM = 0.07129 μg/ml) in Aspergillus, ketoconazole (GM = 0.02570), and voriconazole (GM = 0.03686 μg/ml) in Candida showed the highest antifungal activity (Table 2). Regarding the CLSI-M59 document for ECV, one A. niger (MIC 8 μg/ml), A. flavus (MIC 2 μg/ml), and A. fumigatus (MIC 2 μg/ml) isolates were non-wild type against itraconazole. A total of 3 A. niger non-wild type isolates with MIC 4 μg/ml against voriconazole were inspected (Table 1). Three C. albicans isolates with high itraconazole MICs (two 8 μg/ml and one 16 μg/ml) were observed (Table 2). Even though the MIC50 of Aspergillus niger for tolnaftate was 0.37 μg/ml, 9 isolates with high MICs (16 μg/ml) were found. Conclusion The foremost commonest yeast isolates in this study, C. parapsilosis, exhibit significant sensitivity to various antifungals, including ketoconazole, voriconazole, tioconazole, amphotericin B, miconazole, fluconazole, and itraconazole. However, contrary to other studies, nystatin had high MICs and is not recommended as an effective drug. Since the pattern of antifungal susceptibility is varied among the cryptic species of Aspergillus sections, we recommend that physicians request a drug susceptibility testing before antibiotic therapy to prevent the development of resistance.