|Year : 2022 | Volume
| Issue : 1 | Page : 4
Pythium keratitis – A menacing masquerade
C V Gopala Raju1, Madhu Uddaraju2
1 Visakha Eye Hospital, Visakhapatnam, Andhra Pradesh, India
2 Dr. Ramana Raju's Vision Tree, Visakhapatnam, Andhra Pradesh, India
|Date of Submission||15-Sep-2022|
|Date of Acceptance||15-Sep-2022|
|Date of Web Publication||05-Oct-2022|
Dr. Madhu Uddaraju
Dr. Ramana Raju's Vision Tree, 10-171/1/1, Revenue Colony, Alluri Sita Rama Raju Marg, Visalakshi Nagar, Visakhapatnam - 530 043, Andhra Pradesh
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Raju C V, Uddaraju M. Pythium keratitis – A menacing masquerade. J Ophthalmol Clin Res 2022;2:4
Pythium keratitis, though recently described in several reports, continues to be a clinical diagnostic enigma and a therapeutic challenge. Pythium insidiosum is a waterborne oomycete that closely mimics fungi with it's hyphate morphology. Lack of ergosterol in the cell wall differentiates it from fungi and rendering it unresponsive to antifungal agents. The exact pathological mechanism by which it causes such a fulminant infection is still poorly understood.
Significant risk factors reported in literature for Indian patients are exposure to contaminated water and vegetative trauma. Sight-threatening infectious keratitis caused typically by pythium can be differentiated from fungal keratitis by the following four features in isolation or combination:
- Tentacular extensions from the ulcer
- Peripheral corneal thinning and early limbal involvement
- Cotton wool deep stromal infiltrates
- Reticular dot infiltrates.
However, atypical presentations can resemble all other causes of infectious keratitis making it very difficult to diagnose and delaying the therapy. Any fungal keratitis that is not responding to maximal medical therapy should raise a high suspicion towards pythium keratitis and should be investigated further with repeat scrapings and cultures.
Corneal scrapings subjected to KOH wet mount or Gram's stain has the three following characteristic features:,>
- Longer hyphae with sparse septations
- Numerous vesicles
- Ribbon-like folding pattern of hyphae.
Blood agar culture is an established standard for diagnosing pythium which grows into cream-colored colonies with zoospore formation that are further confirmed by leaf incarnation method.
Antifungal agents, as mentioned earlier, have a limited role in the management of this tenacious infection. Both in vivo rabbit model studies and in vitro susceptibility studies recommend the following therapeutic agents that have worked effectively in at least 10%–50% of the cases:,,
- Topical linezolid 0.2% (reconstituted) 1 hourly
- Azithromycin eye ointment 1% twice a day
- Oral azithromycin 500 mg once daily for 2 weeks.
The above regimen may be continued for as long as 3 months if signs of resolution are appreciated. Any early sign of worsening of infection in the form of limbal spread, corneal thinning, and deeper stromal spread warrants active intervention in the form of cyanoacrylate glue application for impending perforations and early therapeutic keratoplasty. The reinfection rates posttransplantation could be as high as 50% as per large studies, in which again a few cases may also end up with evisceration and phthisis.
A focused study group from multiple centers across the country should investigate this disease with standardized protocols and performing randomized controlled trials that can give us sturdy and evidence-based recommendations.
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