SEROTYPES OF CRYPTOCOCCUS-NEOFORMANS ISOLATED FROM PATIENTS PRIOR TO AND DURING THE AIDS ERA IN THAILAND

One hundred and eighty-seven strains of Cryptococcus neoformans isolat ed from patients in Thailand were characterized by biochemical varieti es relating to serogroups. Canavanine-glycine-bromothymol blue (CGB) a gar was used for differentiating the varieties of C. neoformans. Slide agglutination tests were performed with Crypto Check (Iatron, Inc., T okyo) to determine their serotypes. Fifty-five percent (10 out of 18) of the pre-AIDS isolates were serotype B, 28% were serotype A, 5% were serotype D, and an unexpected 11% (2 out of 18) were serotype C. Thes e are the first to be recorded in Asia. In contrast, among the 169 cli nical isolates obtained between January 1993 and March 1995 (AIDS epid emic), serotype A was outstandingly predominant-93% (157 out of 169), serotype B was relatively low (3.6%) and both serotypes D and AD were 1.8%. The pattern of serotypes of the 59 isolates from known HIV-posit ive patients was closely similar to the total isolates during the AIDS epidemic. In determining the varieties of C. neoformans by CGB, only 1 of the 187 isolates gave a false reaction. On the basis of our findi ngs, we believe that in the pre-AIDS era either C. neoformans var. gat tii serotype B or serotype C were the common causative agents of crypt ococcosis in Thailand. The advent of AIDS changed the pattern of serot ypes with serotype A becoming predominant as has been reported world w ide.