Coccidioides has been divided into two morphologically indistinguishable species: C. immitis, which is found mostly in the San Joaquin Valley of California, and C. posadasii, which is found outside of California in the southwestern United States (Arizona and New Mexico), as well as parts of Mexico and Central America. The infectious arthroconidia are present in soil, and soil disruption and exposure are risk factors.
Coccidioides spp. is acquired through inhalation of arthroconidia from the environment, which results in pulmonary infection. Organisms can disseminate from the lungs to various sites, including, most commonly, the skin, but also to bones, joints, and the meninges, among others. The immunocompromised are at most risk for dissemination.
In addition to culture, the diagnosis can also be made with an antigen test performed on urine or serum, or with antibody testing.
Coccidioides is a risk to laboratory personnel and can be contracted from laboratory cultures. Any work with Coccidioides spp. mold-form cultures are highly dangerous and, as a consequence, limited manipulations are ideal and must be performed in a biological safety cabinet using BSL-3 work practices. Anything more than tape preparations (e.g., passaging isolates, extracting nucleic acids, etc,) must be done in a BSL-3 laboratory.
The image to the right is a Periodic acid-Schiff (PAS) stain of Coccidioides demonstrating spherules, which contain developing endospores.
Image courtesy of the CDC.
