Exame direto de fungos com KOH

Search for dermatophytes in skin scales and appendages This must always complement the clinical diagnosis of dermatophytosis. The causative agent is identified:–by culture (e.g., on Sabouraud medium), which allows precise identification of the species responsible for the lesions, but requires 2 to 3 weeks, sometimes even longer;–by direct examination of skin scales, which can be performed using two rapid methods but does not allow for precise identification of the species of dermatophyte involved. This involves collecting skin scales, as fine as possible, preferably by scraping the edge of the lesion with a scalpel blade or a blunt curette. In the case of vesicular dermatophytosis, the direct examination should focus on the roof of a vesicle, which is cut off using a scalpel blade. Direct examination of hair or nail shavings follows the same principles. The skin flakes are placed in the center of a glass slide. The scales are then covered with a 10% or 20% KOH solution and a cover slip, and examined under a light microscope with a two-thirds diaphragm. The mycelial filaments appear as tubular, septate, greenish to yellowish formations. The spores and yeasts are rounded or oval. The scales can also be covered with a drop of Na2S-Blankophor P fluessig (Bayer) solution and then examined under a fluorescence microscope (400-440 nm). This fluorochrome is specific to the cell wall of fungi.