Cryptococcus yeast causes a very serious meningitis. The virulence factor of cryptococcus is its capsule which is antiphagocytic. Cryptococcus is transmitted most commonly through pigeon droppings , scattered in air dust. Respiratory symptoms begin first, then the yeast gets into brain lining. The inflammatory reaction is serious and the infection is often fatal.
Cryptococcal meningitis is hard to treat, so it is very serious.
Diagnosis is with a negative stain looking for the capsule in CSF of suspected cases. This fungal microbe used to be called a protozoan. Pneumocystis infection were rare until AIDs. Pneumocystis is the most common fatal infection in AIDs patients and in chemotheraphy patients. Fungal infections are hard to treat and the microbes are ubiquitous in the environment.