The brown colour effect (BCE) of Cryptococcus neoformans in the diagnosis, control and epidemiology of C. neoformans infections in AIDS patients.

Cryptococcus neoformans was found as the causative agent of cryptococcosis in 7 (3.6%) out of 195 HIV-positive persons, most of them being hospitalized. These 7 persons included 6 homosexuals and 1 heroin addict. The examinations were performed at the Mycology Unit of the Robert Koch Institute in Berlin (West) between 1984 and 1986. The brown colour effect (BCE) of the C. neoformans colonies on Guizotia abyssinica creatinine agar (with 0.1% glucose) within 2-5 days at 26 degrees C facilitated the diagnosis of disseminated cryptococcosis. In all 7 cryptococcosis cases, the antigen of C. neoformans was detected in serum and CSF by the latex agglutination test. The initial titres ranged from 1:100,000 to 1:160 in the serum and from 1:1280 to 1:10 in the CSF. In comparison to the progressive stage of the infection with the involvement of the various organs and high antigen titres, the fungus may be detected at an early stage in the respiratory tract only where low antigen titres are observed. All the C. neoformans isolates were found to belong to the variety neoformans. Proposals for an effective control of cryptococcosis are made.