Ubiquitous organism in soil rich in organic nutrients such as decaying vegetation and bird droppings.
It is a basidiomycetous yeast that is unique among pathogens, in that it has an immune shielding polysaccharide capsule, and the cell wall laccase with broad immunomodulatory properties, which which together predispose the organism to neurotropism.
Cryptococcus is an opportunistic antigen that is not transmitted from patient to patient.
A vigorous adaptive immune response that includes CD4 positive helper T cells is required to control the fungal because of iis polysaccharide capsule, which suppresses the innate immune recognition of the fungus.
The Cryptococcus fungus, resists macrophage killing by capsularshedding, which facilities its survival, replication, and exocytosis to permit brain dissemination.
Its polysaccharide capsule prevents desiccation and killing by amoebas in the environment and is the key factor accounting for virulence in infections.
The cell wall contains copper oxidase laccase that facilitates its growth and virulence against plants and produces dopamine products and immunomodulatory oxylipids.
Survival of cryptococcal cells in the environment and in hosts depends on the presence of its capsule and the production of the antioxidant melanin.
4 serotypes of Cryptococcus neoformans, A, B, C and D.
Groups A and D are dominant species worldwide.
Cryptococcal cells are yeasts.
Cells have small capsules.
Cryptococcosis an infection most often seen in the US in patients with advanced HIV infection.
Cryptococcus neoformans is the predominant cause of infections worldwide both in persons living with acquired HIV and in other immunosuppressed populations.
C.gatti
Associated with HIV infection, idiopathic CD4 lymphocytopenia, transplantation, malignancy, connective tissue disease, glucocorticosteroid therapy, COPD, cirrhosis, and sarcoidosis.
Glucocorticosteroid therapy associated with up to 30% of cases of cryptococcal infections in patients who are HIV negative.
C.gatti is a second species.
Infection begins with inhalation of basidiospores of the fungus.
Diagnosis requires biopsy as crytotococcal antigen assay is inadequate.