Dematiaceous fungal keratitis: prevalence, spectrum, clinical features, outcome, and antifungal susceptibility from a tertiary care centre in North India

Fungal keratitis is a sight threatening corneal infection that leads to corneal blindness. Dematiaceous fungal keratitis (DFK) emerged as the predominant cause of fungal keratitis followed by Aspergillus spp. and Fusarium spp. This study aimed the prevalence, species distribution, associated clinical features, risk factors and antifungal susceptibility for keratitis caused by dematiaceous fungi. A prospective study was conducted on suspected fungal keratitis (FK) patients from June 2023 through November 2025 at PGIMER Chandigarh. The corneal samples were processed for routine mycological investigations, including direct microscopy (KOH mount) and culture on SDA (Sabouraud's Dextrose agar), further confirmed by DNA sequencing. Antifungal susceptibility testing (AFST) was performed as per the CLSI (Clinical Laboratory and Standards Institute) broth microdilution method (M38-A2) for a panel of 9 drugs including voriconazole, itraconazole, posaconazole, luliconazole, miconazole, ketoconazole, amphotericin-B, natamycin and terbinafine. Among 1931 suspected FK patients, 452 were confirmed FK where 75 were DFK and prevalence of DFK was calculated 3.8%. Curvularia spp. was found to be most prevalent (n = 39,52%), followed by Alternaria spp.(n = 9, 12%), Colletotrichum spp. (n = 8,10.66%), and Exserohilum spp. (n = 6, 8%) along with 8 other rare genera were isolated. Redness, watering and a decrease in vision were significantly more common in DFK. Amongst the triazoles, voriconazole showed low MIC range of 0.03-16 µg/ml. AFST also demonstrated low MICs to luliconazole and terbinafine. The present study showed a prevalence of 3.88% DFK in North India with Curvularia spp. as the predominant causative agent. In vitro susceptibility of voriconazole demonstrated better performance against DFK isolates.