I recently attended a mycology workshop and several of the participants mentioned ruling out Coccidioides immitis by using media containing cycloheximide.
Currently if we have a white spreading mould that will not sporulate, we do a probe to verify Coccidioides or rule it out.
Can we screen those using a simpler and cheaper test?
Coccidioides immitis is a thermally dimorphic fungus that is resistant to cycloheximide.
Therefore, incorporation of cycloheximide into the growth medium would discourage or inhibit the growth of most moulds, but would still allow Coccidioides spp to grow.
Unfortunately, several other fungi, including Blastomyces dermatitidis, Paracoccidioides brasiliensis and Sporothrix schenckii will also grow in the presence of cycloheximide.
[Laboratory handbook] In cases where differentiation / identification is not possible using standard culture techniques including differential temperature studies or medium changes, other methodologies such as use of DNA probes or exoantigen tests become much more valuable identification tools. [Hayden, 1231, 1178, 1353]
Laboratory Handbook of Medical Mycology, Michael R. McGinnis, 1980, Academic Press, pg. 124.
Hayden RT, Qian X, Roberts GD, Lloyd RV.
In situ hybridization for the identification of yeastlike organisms in tissue section Diagn Mol Pathol. 2001 Mar; 10(1): 15-23