What is the role of cultures in the workup of coccidioidomycosis?

Updated: Aug 27, 2019
  • Author: Duane R Hospenthal, MD, PhD, FACP, FIDSA, FASTMH; Chief Editor: Michael Stuart Bronze, MD  more...
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Answer

The most definitive method for diagnosis is isolation of the organism from clinical specimens. The fungus grows well on most common laboratory media within 3-5 days of inoculation on laboratory media, even when spherules are not present on direct examination. However, the morphology of the colonies (white and cottony mold) is not adequate for identification because other organisms have similar mycelial forms.

Observation of typical arthroconidia may be used to identify the Coccidioides organism.

Identification can be confirmed with a commercially available nucleic acid (gene) probe. Confirmation with exoantigen testing may also be performed, although this test has been replaced by nucleic acid probes. Culture of the organism and definitive identification takes up to 3 weeks.

In culture, Coccidioides spherules can convert to arthroconidia, which are highly contagious. For that reason, cultures should be performed only in Biosafety level 3 laboratories.


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