Morphology

MORPHOLOGY
  • In the soil, C. immitis is a mould made up of slender septate hyphae that give rise, on thicker secondary branches, to chains of infectious arthroconidia (arthrospores, arthroaleuriospores, arthroaleurioconidia).
  • These are bulging, thick-walled cells, separated by empty cells, through which breaks occur when arthroconidia are dispersed.
  • In tissue, arthroconidia grow into spherical sporangia with birefringent walls, "spherules", which by internal cleavage produce several hundred "endospores".
  • The walls disintegrate, allowing dissemination of endospores, each of which may repeat the cycle or, on a nonliving substrate, give rise to mycelial growth.
  • Though only arthroconidia are naturally infectious, endospores can experimentally initiate disease. Sexual spores are not known.
  • "Coccidioidin" in supernatants of mycelial C. immitis broth cultures is largely polysaccharide, but contains some amino acid nitrogen.
  • It is used in cutaneous hypersensitivity and serologic tests.
  • "Spherulin," a lysate of cultured spherules, is also used in skin tests. Both are leukotactic.
Last modified: Monday, 4 June 2012, 6:34 AM