Coccidioides immitis

MICROBIOLOGY

• Causative organisms and endemic regions
  • Coccidioides immitis: Primarily found in the Central Valley of California, but pockets are as far north as eastern Washington state.
  • Coccidioides posadasii: Primarily foundin the desert areas of Arizona, Texas, Utah, Mexico, and Central and South America
  • Both species can be found in Southern California
• Dimorphic fungal characteristics [Fig 1]:
  • Environmental form: filamentous with septated hyphae that grow in soil. When a dry spell follows rain, the hyphae become brittle, and small (~3-5 μm in diameter) fungal particles termed arthroconidia break off, become airborne, and potentially inhaled.
  • Invasive form at 37°C: following inhalation or occasionally via percutaneous entry, arthroconidia transform into large (~60-75 µm in diameter) structures termed spherules that contain hundreds of small (~2-5 µm in diameter) structures termed endospores. When the mature spherules rupture, endospores are released, which can, in turn, form additional spherules [Fig 2].
• Environmental conditions
  • Preferentially grows in regions of California, Southwest U.S. and parts of Mexico that have hot summers, moderate winters and little rainfall.
  • Isolated pockets of C. posadasii are also found in parts of South and Central America.
  • Growth of the fungus as far north as central Washington state has been described.
  • The environmental reservoir is suspected to involve rodents
• Micro: grows readily on standard fungal media.
  • Coccidioides grown in culture can be a significant laboratory hazard and must be handled cautiously in an appropriate safety cabinet.
    • When submitting specimens, alert the micro lab if suspected.