Renaissance of an Emerging Pathogen-Pythium insidiosum Keratitis: An Indian Perspective

Area of Science:

• Ophthalmology
• Infectious Diseases
• Medical Mycology

Background:

• Pythium insidiosum keratitis is an aggressive, vision-threatening corneal infection prevalent in India, especially among agricultural workers.
• It is frequently misclassified as fungal keratitis due to its unique cell wall composition, leading to delayed and ineffective antifungal treatment.
• The oomycete's resistance to conventional antifungals stems from its cellulose/β-glucan wall and lack of ergosterol, resulting in rapid stromal melt.

Purpose of the Study:

• To review the epidemiology, clinical diagnostics, immunopathogenesis, and management of Pythium insidiosum keratitis in India.
• To synthesize India-derived insights into a pragmatic framework for managing this infection globally.
• To highlight future research priorities for Pythium keratitis.

Main Methods:

• Review of epidemiological data and clinical case series from India.
• Analysis of diagnostic signatures, laboratory findings (microscopy, culture, PCR), and immunological insights.
• Synthesis of current management strategies, including surgical and medical interventions.

Main Results:

• Distinct clinical diagnostic signatures include peripheral infiltrates, early endothelial plaque, and hypopyon.
• Microscopy reveals ribbon-like hyphae; culture is variable; PCR confirms species.
• Management often involves a surgery-first approach (therapeutic keratoplasty) combined with topical linezolid, azithromycin, and supportive care.

Conclusions:

• Early and accurate diagnosis is crucial for Pythium keratitis, differentiating it from fungal infections.
• A surgery-first strategy coupled with targeted medical therapy improves visual outcomes.
• Future directions include point-of-care diagnostics, standardized susceptibility testing, and immunomodulatory therapies.