Los métodos de laboratorio en el diagnóstico de la coccidioidomicosis

Coccidioidomycosis: skin manifestations and hypersensitivity syndromes

“…The spherules are seen as spherical elements with thick walls, 5-60 µm, with numerous, small, globular endospores of 2-5 µm in their interior (4). Gomori-Grocott stain is the most useful, in which the fungus turns black, on a green background (43,44). They may be a diagnostic challenge because they can be easily confused with Histoplasma spp., Blastomyces spp.…”

“…Direct examination: Direct microscopical examination of the secretions (alveolar aspirate, cerebrospinal fluid, exudate) stained with calcofluor-white (which joins the chitin or cellulose of the cell wall) and observed in a fluorescence microscope, allow the visualizing the spherules with a 22% sensitivity. The KOH test may be diagnostic when spherules are observed, but even though it is easy to perform, it has lower sensitivity than calcofluor-white stain and requires an experimented observer (43,44). Culture: The fungus may be isolated in many specimens, with respiratory tract secretions being the ones that produce more positive ratios (8.3% in one study), and blood and cerebrospinal fluid cultures the ones with the lowest isolation.…”

“…If Coccidioides ssp. is found the drug sensitivity study is not performed because no isolates resistant to conventional treatment have been evidenced (43). Laboratory management is of very high risk due to its high biotic potential, reason why it requires third security level laboratory management (2).…”

“…The immunoassay has a sensitivity of 83%. If the result is negative, it does not require confirmation, but if it is positive, it requires confirmation with immunodiffusion in agar gel, which has a sensitivity of 71% (43).…”

“…Intradermoreaction with coccidioidin: It consists of an intradermal injection with 0.1 ml of a standardized micellar coccidioidin. The cutaneous induration reaction is measured after 48 hours, and it is considered positive when the diameter is 5 mm or more (43). This is only useful for population studies because it does not distinguish between acute disease and previous exposure to the fungus (6).…”