Cryptococcus neoformans
Yeast
Worldwide distribution often found in soil contaminated with bird excrement, in particular, pigeon droppings have frequently been implicated.
Cryptococcus neoformans is a rapidly growing typically round yeast (5-10µm) capable of producing polysaccharide capsules which often surround the cell. A 1% peptone solution might aid encourage capsule production. Some species &/or strains of Cryptococcus will not produce capsules in-vitro. Capsule production is best demonstrated using the India-ink (or Nigrosen) negative staining technique. Colonies producing capsules on culture are often evident by their glistening wet or mucoid appearance whereas colonies which fail to produce capsules or have diminished ability to form capsules typically produce dull, creamy, butyrous colonies. Cryptococcus neoformans can be sub-typed further based on serological response to capsular antigens.