Evaluation of Calcofluor staining in the diagnosis of fungal corneal ulcer

Abstract

For laboratory diagnosis of mycotic keratitis, demonstration of fungal pathogens on direct microscopy and their isolation by culture is essential. The addition of Calcofluor white (CFW) stain to the diagnostic armamentarium has significantly increased the sensitivity of smear examination on direct microscopy. During a period of 1 year, 143 consecutive patients with corneal ulcers were investigated by direct microscopy with potassium hydroxide (KOH) wet mount, Calcofluor white stain and routine cultures of corneal scrapings. Fungi were detected as aetiological agents in 21 (15%) patients. Different species of the genera Aspergillus (35%), Fusarium (23%), Acremonium (12%), Paecilomyces (12%), Cladosporium (6%), Alternaria (6%) and Pseudallescheria (6%) were the common isolates. Calcofluor white stain on direct microscopy detected fungi in 20 (95.2%) patients in comparison with 15 (71.4%) patients by both KOH wet mount examination and culture. Calcofluor white stain was significantly more sensitive than KOH wet mount in demonstrating fungal pathogens.