Black Grain Eumycetoma Revisited: Enhanced Fungal Isolation by Use of a Novel Technique

Abstract

Background: Dematiaceous fungi or brown-black fungi distributed worldwide are being increasingly recognized as pathogens of importance. Found in soil, they have unique pathogenic mechanisms owing to the presence of melanin in their cell walls, which imparts the characteristic dark color to their spores and hyphae. Eumycetoma is a common, chronic, granulomatous infection that is present worldwide and endemic in tropical and subtropical regions. Black grain eumycetoma accounts for about 95% of eumycetomas in India. Isolation of the causative fungus from the coloured grains in the laboratory is an arduous task resulting in empirical treatment. At present, clear evidence based treatment recommendations are unavailable and it becomes pertinent to identify, isolate and speciate the causative fungus so that appropriate treatment can be instituted for complete resolution.Objective: This article revisits black grain mycetoma in the larger spectrum of phaeohyphomycosis, describes four patients with black grain mycetoma and elaborates on a novel technique developed in our laboratory for assured isolation of fungi from eumycotic "grains".Clinical management: All four patients gave a clinical history of mycetoma, having observed intermittent discharge of black grains from lesions. Processing of grains was comprehensively carried out with direct KOH preparation, mycological analysis of the grains and histology. All patients were started on oral itraconazole 200-400 mg twice daily, post wide excision of soft tissue that resulted in near complete regression of the lesion. Summary:Timely identification of the fungal isolate based on grain morphology and culture in a setting where molecular setup and techniques are not available is crucial to ensure guided therapy and best clinical outcomes for the patient.

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“…Although culture and molecular identification of the causative pathogen is considered the gold standard for diagnosis of mycetoma, culturing is rarely performed even in highly specialized centers [10,5]. One of the reasons is that mycetoma agents require several weeks to grow, and risks of absence of growth or contamination are very high [10,21]. Recently, culture-free methods have been introduced for direct detection of agents of eumycetoma in clinical materials.…”