Pythium keratitis: Clinical profile, laboratory diagnosis, treatment, and histopathology features post-treatment at a tertiary eye care center in Eastern India

Abstract

Purpose: The aim of this work was to study demography, clinical profile, laboratory diagnosis, and management of Pythium keratitis at a tertiary eye care center in Eastern India.

Methods: Eighteen patients with culture-positive Pythium keratitis managed at our center between January 2016 and December 2018 were included in this retrospective study. Clinical features, laboratory investigations, treatment, and outcomes were analysed.

Results: Pythium keratitis commonly affects middle-aged males with low socioeconomic profile and history of trauma. Samples stained with Gomori methenamine silver showed 93.8% positivity and Iodine-potassium iodide-sulfuric acid showed 100% positivity. Periodic acid-Schiff's showed negative staining in 62.5% and weak in 37.5%. Kirby-Bauer disc diffusion method showed zone of inhibition as 30.25 ± 4.61 mm for Linezolid and 23.56 ± 6.86 mm for Azithromycin. Medical management included topical/oral linezolid and azithromycin. Therapeutic penetrating keratoplasty (TPK) was done in 15 eyes (83.3%), repeat TPK in 4 eyes, and evisceration in 3 eyes (16.7%). One patient required only medical treatment. Globe salvation was obtained in 15 (83.3%) eyes, and good visual outcome in 7 eyes (38. 9%). There was graft failure in six eyes (40%) and two (11.1%) eyes went into phthisis. Patients were divided into early and late presenters. Late presenters had more complications and worse final visual outcome.

Conclusion: Pythium keratitis can be differentiated from fungal keratitis by its characteristic appearance on slit-lamp examination, smear, culture, and histopathology. Early presentation, detection, and treatment with antibacterial drugs like linezolid and azithromycin results in a better prognosis. Early full-thickness corneal transplant should be considered for Pythium keratitis not responding to treatment.

Keywords: Fungus; Pythium; keratitis.

Figure 1

(a-h): Slit-lamp picture of total and near-total corneal infiltrate (a and b); corneal perforation (c); ring infiltrate (d); Direct microscopy of corneal scrapings revealing broad, aseptate, hyaline filaments with ribbon-like folds in KOH + CFW, 40x (e); Photomicrograph of corneal tissue with full thickness involvement by filamentous structures extending from Bowman's membrane (Asterix marked), GMS (30X) (f;) Bluish black filaments, IKI-H2SO4 stain (40X) (g); Perforated cornea with diffuse stromal necrosis and fragmented Descemet membrane (arrow marked). Posterior stromal histiocytes and multinucleated giant cell noted (circle), PAS (40X) (h)