Fungal keratitis: Rapid diagnosis using methylene blue stain

Abstract

Earlier and accurate diagnosis of the fungal infection in the cornea is necessary for effective treatment. In developing countries, microscopical evaluation is the most valuable and rapid diagnostic tool. Therefore we aimed to investigate the efficacy of methylene blue (MB) staining in comparison with potassium hydroxide (KOH) and calcofluor white (CW) stain. Corneal scraping from 48 cases with suspected fungal keratitis were included in the study from January 2014 to December 2014. The specimens were subjected to direct examination by MB, 10% KOH and CW stain. The staining results were confirmed with fungal culture and strain identification. Topical amphotericin B was started for all positive fungal cases; 39 (81.25%) were proven fungal cases. Positive rate of calcofluor white, MB and 10% KOH staining were 79.2%, 75% and 68.75% respectively. CW showed higher sensitivity and specificity (99.44% and 90.91% respectively), followed by MB (92.31% and 80.0% respectively) and lastly KOH 10% (84.62% and 71.43% respectively). 71.8% of cases had healed scars and only 4 patients (10.3%) required keratoplasty (PK). Direct microscopic detection of fungal structures by MB staining in corneal scrapes is a fast and effective method for the early diagnosis of fungal keratitis.

Diagnostic utility of Gram staining for infectious keratitis

“…Sin tratamiento adecuado, la infección corneal conduce a ceguera a través de cicatrices corneales y endoftalmitis. Las bacterias y los hongos se encuentran entre los agentes etiológicos frecuentes responsables de queratitis (Khokhar, Mulla, Shah, & Vaghela, 2013;Moemen, Bedir, Awad, & Ellayeh, 2015).…”

“…Es de distribución mundial, pero es más común en las regiones tropicales y subtropicales, 6 a 60% de las queratitis observadas son de etiología micótica, dependiendo principalmente de la localización geográfica, en algunos países en desarrollo representa aproximadamente el 50% de todos los casos de queratitis microbiana obtenidos en cultivo (Ibrahim et al, 2011;Samudio et al, 2014). Se considera una infección oportunista asociada principalmente a trauma ocular con materiales vegetales (Laspina et al, 2004;Moemen et al, 2015;Samudio et al, 2014). En países tropicales como Paraguay, la incidencia de queratitis por hongos es relativamente alta debido a las condiciones climáticas (Laspina et al, 2004;Samudio et al, 2014).…”

“…El cultivo de hongos, requiere tiempo e instalaciones especiales no disponibles en todos los laboratorios, lo que retrasa el tratamiento clínico. Por lo tanto, la detección microscópica directa de estructuras fúngicas en raspados corneales permite un rápido diagnóstico presuntivo (Bharathi et al, 2006;Khokhar et al, 2013;Moemen et al, 2015).…”

Development and Validation of an Hplc Method for Voriconazole Active Substance in Bulk and its Pharmaceutical Formulation

“…ıt shows worldwide spread, but is more common in the tropics and subtropical regions. ın fungal keratitis, early diagnosis and antifungal therapy is necessary in terms of preventing further complications such as hypopyon formation, endophthalmitis, or loss of vision (7). Whilst reports on the use of 1% voriconazole eye drops in the management of ophthalmic fungal keratitis have been promising, the voriconazole concentrations achieved in the eye were not sufficiently high to treat all types of fungal keratitis (8).…”

A Case of Rhizopus Keratitis

“…However it requires a specialized equipment that is not available in all centers. Direct microscopic detection of fungal structures by methylene blue staining in corneal scrapes is another fast and effective method for early diagnosis of fungal keratitis [9,10].…”