Abstract: Objective To investigate genetic relationships among five serotypes of two variants of Cryptococcus neoformans. Methods PCR mediated DGGE (denaturing gradient gel electrophoresis) and sequence analysis of 28S rDNA of C. neoformans were performed in ten reference strains, C. neoformans capsular-deficient strain CAP10, and nineteen clinical isolates from non-HIV patients. Results The results of DGGE and analysis of nucleotide sequences of 28S rDNA showed identical patterns and nucleotide sequences in the serotype A and D of C. neoformans var. neoformans, which were distinct from the serotye B and C of C. neoformans var. gattii. The patterns and sequences of serotype AD coincided with those of C. neoformans var. gattii. The patterns and nucleotide sequences of C. neoformans capsular-deficient strain CAP10 (serotype D) and serotype A and D were identical. Of the nineteen clinical isolates, seventeen had patterns of serotype A and D, and the others had patterns of serotype B and C. Conclusions PCR mediated DGGE integrated with sequence analysis of 28S rDNA is a valuable tool for the classification of C. neoformans. The clinical isolate of C. neoformans var. neoformans is predominant in Chinese non-HIV patients. Serotype AD is genetically close to C. neoformans var. gattii rather than C. neoformans var. neoformans. The data seem not to be in favor of previous study that serotype A, C. neoformans var. grubii, is a new variant of C. neoformans.

Key words: Cryptococcus neoformans, DNA, fungal, Sequence analysis, DNA