Newer Emerging Pathogens of Ocular Non-Sporulating Molds (NSM) Identified by Polymerase Chain Reaction (PCR)-Based DNA Sequencing Technique Targeting Internal Transcribed Spacer (ITS) Region

Abstract

Purpose: To apply Polymerase Chain Reaction (PCR)-based DNA sequencing targeting Internal Transcribed Spacer (ITS) region for identification of non-sporulating molds (NSM) to species level which formed 12% of ocular isolates of fungi in a tertiary eye hospital in South India. Materials and Methods:Fifty ocular filamentous fungal NSM isolates recovered from 45 patients were included in the study. PCR-based DNA sequencing technique targeting ITS region was applied to identify NSM. Results: PCR-based DNA sequencing revealed 23 established pathogens involving 8 genera (Aspergillus, Fusarium, Bipolaris, Pythium, Cochilobolus, Exserohilum, Pseudoallescheria, and Scedosporiumspecies) and 27 emerging pathogens involving 7 genera (Botryosphaeria Lasiodiplodia species, Thielavia tortuosa, Glomerulla singulata, Macrophomina phaseolina, Rhizoctonia bataticola, and Podosporaspecies) reported for the first time in literature related to ocular infections. Fifteen (30%) patients with fungal keratitis caused by NSM failed to respond to standard antifungal therapy. Conclusion: PCR-based DNA sequencing technique is a rapid, reliable, and valuable tool to identify 54% of NSM as newer potential pathogens of fungi causing ocular mycoses.

KEYWORDS:

• non-sporulating molds (NSM)
• internal transcribed spacer (ITS) region
• polymerase chain reaction (PCR)
• DNA sequencing
• fungal keratitis
• Botryosphaeria species