Coccidioides immitis

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Coccidioides immitis
Tissue Spherules Methenamine Silver Stain
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Coccidioides immitis

• Skin scrapings should be examined using 10 KOH
  and Parker ink or calcofluor white mounts
• Exudates and body fluids should be centrifuged
  and the sediment examined using either 10 KOH
  and Parker ink or calcofluor white mounts,
• Tissue sections should be stained using PAS
  digest, Grocott's methenamine silver (GMS) or
  Gram stain
• You dont have to remember these methods for me.

3
Coccidioidomycosis

• Identification of C. immitis
• Young mould colonies are white and glabrous to
  cottony with age becoming tan to brown or gray
  grows faster than most dimorphics. May have light
  front and pigmented back like Histoplasma.
• As mentioned above they do not grow as yeast on
  the BHI blood agar the way other dimorphics do.
  The answer?

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Coccidiodes immitis
Reverse
Front
SDA Room Temperature
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Coccidioidomycosis

• Identification of C. immitis
• Demonstration of C. immitis exoantigen derived
  from mold cultures is the safest and fastest
  method of identifying C. immitis
• Microscopically the mould shows one-celled
  thin-walled, barrel-shaped arthroconidia
  alternating between hyaline hyphal cells
  (disjunctor cells An empty cell that fragments
  and/or undergoes lysis to release a conidium )

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Coccidoides immitis

Slide Culture Potato Dextrose Agar Room
Temperature
7
More disjunctor cells
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Coccidioidomycosis

• Identification of C. immitis
• This is known as a complex arthroconidium
• Simpler arthroconidia in fungi such as Geotrichum
  sp. do not have disjunctor cells
• Malbranchia and Gymnoascus are nonpathogenic
  moulds with very similar in vitro morphology to
  C. immitis

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Gymnoascus Species
Slide Culture Potato Dextrose Agar Room
Temperature
10
Coccidioidomycosis

• Identification of C. immitis
• In contrast to C. immitis, the saprobic species
  grow very rapidly, are not dimorphic, will not
  form a spherules, and are negative for the
  exoantigen test