[Laboratory methods in the diagnosis of coccidioidomycosis]

Coccidioides immitis and Coccidioides posadasii, the two recognized causes of coccidioidomicosis, may be diagnosed by direct microscopy, culture, serologic and the skin-test with mycelial coccidioidin. Identification of spherules by direct examination of secretions after addition of KOH, is more rapid and may speed diagnosis. Histopathology of infected tissue demonstrates acute and chronic granulomatous inflammation and in the section strained with hematoxylin-eosine (HE) or Grocott metamine-silver (GMS). Isolation of Coccidioides spp. by culture is not difficult, the fungus grows well on most mycologic media after 5-7 days of incubation and the laboratory should maintain a biological safety level 2 or 3. Phenotypic identification to genus level may be achieved by visualization of arthroconidia in culture. Isolates may be confirmed as Coccidioides ssp. by molecular probes, but separation of species is best achieved by specialized molecular techniques, available at the Reference Laboratory. Immune diffusion and enzyme-immune assays (EIA) are commonly used for detection of IgM and IgG antibodies in serum. Sequential complement fixations (CF) for IgG class of antibody are useful for the prognosis of coccidioidomycosis.