Malbranchea pulchella
Malbranchea species are soil fungi of worldwide distribution which microscopically may resemble Coccidioides immitis/posadasii.
Note: Culture identification by exoantigen test or ITS sequencing is the method of choice for identification of C. immitis/posadasii.
Malbranchea pulchella arthroconidia produced in tightly coiled, terminal fertile branches of the hyphae.
RG-1 organism.
Morphological description:
Colonies are white to sulphur-yellow to ochre-brown in colour, suede-like in texture, with a reddish-brown reverse, and often a reddish diffusible pigment. Microscopic morphology shows typical hyaline, one-celled, cylindrical, truncate, alternate arthroconidia produced in tightly coiled, terminal fertile branches of the hyphae. Arthroconidia are released by lysis of the disjunctor cells. These arthroconidia may be perceived as a yellow dust when released at maturity.
Key features:
Hyphomycete producing alternate arthroconidia with disjunctor cells.
References:
Cooney and Emerson (1964), Sigler and Carmichael (1976), McGinnis (1980), Rippon (1988), de Hoog et al. (2000, 2015).