What is cryptococcosis

Cryptococcosis

1 definition

Under one Cryptococcosis one understands an infection with the encapsulated fungus Cryptococcus neoformans, which occurs mainly as an opportunistic infection in immunosuppressed patients.

2 epidemiology

Cryptococci are found on grain as well as in the soil and on grass. The blades of grass and seeds populated with fungi are taken in by birds and excreted through their excrement. An important source of infection for humans is pigeon droppings.

3 pathogenesis

Cryptococcus neoformans has a capsule made of polysaccharides that protects the fungus from phagocytosis by granulocytes and macrophages. The melanin stored in the fungal cell wall prevents the fungus from being oxidized by the products of macrophages.

The pathogens are absorbed by inhalation of contaminated dust. The infection of the lungs with the formation of granulomas often remains without symptoms; In patients with a weakened immune system, it is spread to other organs, especially the CNS. It is possible that organs are affected that cannot be reached by cells of the immune system or by drugs (e.g. prostate), which can lead to endogenous reinfection due to a weak immune system

The infection of the CNS also initially proceeds without symptoms. In the CNS, Cryptococcus neoformans multiply and granulomas develop. The meningoencephalitis caused by the fungus develops slowly.

Infestation of the skin is possible, but rarely occurs.

4 clinic

The infection of the lungs usually remains asymptomatic; meningitis or meningoencephalitis can develop in the CNS region in a patient with a weakened immune system.

5 evidence

Cryptococcus neoformans can be detected in CSF, serum, urine and bronchoalveolar lavage (BAL). Fast and targeted diagnostics play an important role, especially when meningoencephalitis is suspected to be caused by Cryptococcus neoformans.

5.1 Direct pathogen detection

The direct pathogen detection is primarily carried out microscopically via phase contrast microscopy and the preparation of an ink preparation. The fungal cells displace the ink through their capsule, so that microscopically a bright halo around the pathogen can be seen.

The cultural detection of Cryptococcus neoformans is also possible, but takes several days and requires special culture media (e.g. Sabouraud agar). Characteristic is the formation of dark pigmented colonies due to the formation of melanin.

Antigen detection can also be carried out using ELISA and latex particle agglutination tests or detection of the pathogen DNA using real-time PCR from liquor, urine, serum and BAL.

The fact that Cryptococcus neoformans breaks down urea in its metabolism serves to distinguish it from other yeasts. The fungus is best identified biochemically by its clear urease formation.

5.2 Indirect pathogen detection

Methods for indirect pathogen detection (antibody detection) are available for infections with Cryptococcus neoformans, but they play a subordinate role.

6 therapy

Cryptococcosis is treated with a triple combination of flucytosine, amphotericin B and fluconazole over a period of four to eight weeks, since the drug liquor is widely available and can therefore be used very well for the treatment of meningoencephalitis.

Lifelong therapy, e.g. with fluconazole, is mandatory for affected men, as reactivation from the prostate is possible.

7 prophylaxis

Prophylaxis is possible by containing the pigeon plague.

8 literature