As the mycelia mature, arthroconidia
are formed which become airborne and either return to the soil or are inhaled.
As the weather dries, arthroconidia
break off and become airborne spores when the soil is disrupted (7).
Coccidioides immitis can cause clinically significant disease after inhalation of only a few arthroconidia
It produces septate hyphae, arthroconidia
, and yeastlike growth on culture media.
The organism lives in soil as filamentous mycelia that break down into arthroconidia
, which can be carried on the wind and inhaled.
Microscopic evaluation of the fungal culture showed chains of barrel-shaped arthroconidia
suggestive of Coccidioides spp.
Every year, [approximately equal to] 3% of area inhabitants become infected (3) through inhalation of airborne arthroconidia
(spores), which results in mild to severe febrile respiratory illness (4,5).
It can have widely separated hyphal segments mimicking C immitis, but these segments are typically not as large in diameter, do not bulge outside the diameter of the hyphae, and are not barrel-shaped or thick-walled, as is the case for C immitis arthroconidia
Therefore, a urease-positive yeast that forms arthroconidia
can be presumptively identified as a Trichosporon species.
Microscopic analysis showed hyaline septate hyphae and arthroconidia
alternating with empty disjunctor cells (Figure, panel B).
Infection is acquired by inhalation of arthroconidia
, or spores, and exposure to dust in endemic areas produces a higher incidence of the disease.
Coccidioidomycosis, or valley fever, is acquired by inhalation of arthroconidia
in desert soil in the southwestern United States.