Characteristics;
Urease Test Positive: (urea split to release ammonia which raises the pH of the phenol red indicator in the media turning it from a straw colour to a bright pink.)
C.neoformans and other Cryptococci inhibited by Cycloheximide.
C.neoformans can be differentiated from other Cryptococcus species using the Caffeic acid test (a substance used as a substrate to demonstrate phenoloxidase activity. If phenoloxidase is present, it breaks down caffeic acid to melanin with resulting brown-black colour production.) Note: phenoloxidase is inhibited by the presence of glucose so culture the yeast on a glucose-free media such as Cornmeal-Tween 80 agar.
C.neoformans grows well at 25oC as well as 37oC. Some other Cryptococcus species will not grow at 37oC.
Cryptococcus neoformans & most other Cryptococcus species do not produce pseudohyphae.
Clinical Manifistations;
Cryptococcus infections can be found with increasing frequency amongst HIV patients and others who are immunocomprimised however Johns Hopkins Medical center has noted an interesting pattern regarding the serotypes of C.neoformans.
C.neoformans v. neoformans is the most common, usually afflicting immunocompromised hosts while C.neoformans v. gattii is most common in immunocompetent hosts.
Cryptococcus neoformans infection is primarily acquired through inhalation and may invade;
Respiratory system - (Sputum, Broncheal Wash, Lung Biopsy)
Central Nervous System (CNS) - (Lumbar Puncture)
Also implicated in;
Skin infections
Bone infections
Other sites (disseminated)