Cultural characteristics and resistance

CUTURAL CHARACTERISTICS AND RESISTANCE

Cultural characteristics

  • This dimorphic fungus grows more quickly than the other dimorphic pathogens (1-2 weeks), but the same cultivation media are used.
  • On Sabouraud's or blood agar, at 25° C or 37° C, a moist white colony develops that later is covered with a fluffy mycelium. Bovine blood agar is hemolyzed.
  • Arthroconidia are produced in 5 to 7 days. Mycelial growth should be evident within a week and is examined for presence of arthroconidia in a lactophenol cotton blue wet mount.
  • Thick-walled, barrel-shaped arthroconidia alternating with empty disjunctor cells is characteristic.
  • The isolate can be reconverted to the sporangial phase by animal inoculation or cultivation in a spherule medium.
  • The sporangial phase is produced at 40°C in media containing casein hydrolysate, glucose, biotin, glutathione and a salt mixture.

Resistance

  • Arthroconidia resist drying and tolerate heat and salin­ity better than do competing soil organisms.
  • In summer heat, C. immitis survives in soil layers nearer the surface than its competitors.
  • When conditions favor growth again after rains, C. immitis repopulates the superficial soil layers first, ensuring its widespread dispersal.
Last modified: Monday, 4 June 2012, 6:34 AM