Etiologic agent =
Cryptococcus neoformans var. neoformans
Unlike Blastomyces, Histoplasma and Coccidioides,
CRYPTOCOCCUS IS NOT A DIMORPHIC FUNGUS; IT ALWAYS EXISTS
IN A YEAST FORM.
- Nonetheless, handling infected animals is still not considered
an important risk factor for infection with Cryptococcus.
- A THICK, POLYSACCHARIDE CAPSULE is produced after
Cryptococcus organisms enter a host. In vivo, the
capsule may be immunosuppressive and it inhibits phagocytosis.
- Like Histoplasma, this organism prefers soil contaminated
with bird droppings and is often associated with pigeon droppings.
The organism has also been found in the feces of pet canaries,
budgerigars, cockatoos and other psittacine birds, and exposure
to a pet bird has been linked to infection of an immunosuppressed
human transplant patient.
As with the other systemic fungi, infection with Cryptococcus
most often occurs via inhalation of the organism from the environment,
followed by primary pulmonary infection and subsequent systemic
spread.
- Cryptococcus neoformans does not appear to be transmitted
to humans orally, even following consumption of milk from cows
with cryptococcal mastitis.
