Coccidioides immitis

Ascomycota
Scientific classification
Kingdom:	Fungi
Division:	Ascomycota
Class:	Euascomycetes
Order:	Onygenales
Family:	Onygenaceae
Genus:	Coccidioides
Binomial name
Coccidioides immitis G.W. Stiles

Sputum culture of Coccidioides immitis on Sabouraud's medium, showing white, cottony fungus growth.

Coccidioides immitis is a pathogenic fungus that resides in the soil in certain parts of the southwestern United States, northern Mexico, and a few other areas in the Western Hemisphere.

It, along with its relative Coccidioides posadasii, is most commonly seen in the desert regions of the southwestern United States, and in Central and South America. It can cause a disease called coccidioidomycosis (Valley Fever). Coccidioidomycosis is not diagnosed on the basis of signs and symptoms, which are usually vague and nonspecific, or on a chest X-ray, which cannot distinguish valley fever from other lung diseases, including lung cancer. Blood tests are available that test for antibodies against the organism. However, because the organisms create a mass that can mimic a lung tumor, the diagnosis may require a tissue sample (biopsy). A Gomori methenamine silver (GMS) stain can then confirm the presence of the organism's characteristic spherules within the tissue. The Coccidioides immitis organism can be cultured from a patient sample, but the culture can take weeks to grow and requires special precautions by the laboratory. It has been declared a select agent by both the U.S. Department of Health and Human Services and the U.S. Department of Agriculture, and is considered a biosafety level 3 pathogen.

In popular culture

Coccidioides immitis is used as a plot device in Thunderhead, a novel by Douglas Preston and Lincoln Child. The fungus (prepared from infected victims) is revealed to be the principal agent in corpse powder (based on corpse poison used by Witch). It was also mentioned by the fictional antihero Dr. Gregory House (played by actor James Hugh Calum Laurie) on the Television Series, House MD (episode Lines in the Sand).

Microscopic appearance of an old culture of Coccidioides immitis, showing fragmented chlamydospores. This is the infective form of the fungus occurring in nature.

Septate hyphae of Coccidioides immitis with 90 degree branching and thick walled barrel shaped arthroconidia alternating with empty cells.