A 31-year-old female presented with a 3‑week history of right-eye redness, ocular pain, photophobia and decreased vision following exposure to tap water. On slit-lamp examination the corneal lesion demonstrated characteristic features described in the report: visible pseudopodia and a hill‑shaped hypopyon. These clinical signs suggested an infectious keratitis with filamentous elements.
In vivo confocal microscopy (IVCM) of the affected cornea detected filament-like structures within the corneal stroma. Based on clinical appearance and IVCM, the initial working diagnosis was fungal keratitis. Corneal scraping specimens were obtained for microbiology evaluation. When initial management did not halt progression, repeat corneal scraping culture and targeted DNA sequencing were performed, which confirmed infection by Pythium insidiosum.
The patient received standardized antifungal therapy according to the initial clinical diagnosis; however, her condition continued to deteriorate while on antifungal treatment. The case report emphasizes that Pythium species are oomycetes rather than true fungi, a distinction that is clinically important because these organisms are intrinsically resistant to many conventional antifungal agents. In this patient, lack of response to antifungals prompted further microbiologic investigation that established the correct diagnosis by culture and targeted DNA sequencing.
After identification of Pythium insidiosum, medical therapy was changed from antifungal agents to an antibacterial regimen centered on linezolid. The report notes that certain antibacterial drugs, including linezolid, have activity against Pythium species and therefore may be effective where antifungals fail. Despite transition to linezolid-based therapy, the clinical course remained severe and the patient subsequently developed corneal perforation.
Following corneal perforation, the patient underwent a total keratoplasty with placement of a scleral ring. Two weeks after this procedure the infection relapsed. The relapse after keratoplasty highlights the difficulty of eradicating Pythium from ocular tissues and the potential need for adjunctive interventions when surgical reconstruction is performed in the setting of active infection.
To manage the postoperative recurrence, the treating team administered multiple intracameral and intrastromal injections of linezolid. These localized injections, combined with the systemic/ topical antibacterial approach, ultimately controlled the recurrent infection. After infection control, a secondary penetrating keratoplasty was performed as a staged reconstructive procedure.
No recurrence was observed during an 11‑month follow-up period after the secondary keratoplasty. The corneal graft remained transparent and the patient’s best corrected visual acuity improved to 0.6. These outcomes indicate that, even with initial antifungal failure and the need for multiple surgical procedures, infection control and functional visual recovery are achievable when the causative organism is correctly identified and treated with appropriate agents plus individualized surgical care.
This case report reinforces several key clinical points drawn from the authors’ summary:
In patients with suspected filamentous keratitis who do not respond to conventional antifungal therapy, consider Pythium infection in the differential diagnosis.
Early use of targeted DNA sequencing and repeat microbiologic testing can provide rapid and definitive pathogen identification when initial treatment fails.
Recognizing that Pythium are oomycetes with intrinsic resistance to many antifungals should prompt timely transition to effective antibacterial agents such as linezolid once the organism is identified.
Surgical management may be required for structural complications (for example, corneal perforation), but surgery performed without adequate infection control can be followed by relapse; adjunctive local antimicrobial injections may be necessary to eradicate infection and enable successful grafting.
Individualized, staged surgical intervention together with targeted antimicrobial therapy can lead to infection control and satisfactory visual rehabilitation, as evidenced by the successful 11‑month outcome in this case.
Details such as dosing regimens, duration of systemic or topical therapy, specific culture timelines, and intraoperative findings beyond those reported were not provided in the source abstract and therefore are not included here.