Identification by polymerase chain reaction fingerprinting of Cryptococcus neoformans serotype AD

Seventy-three Cryptococcus neoformans isolates and eight other yeast strains were studied. Fingerprints produced by priming with (GACA)4 differentiated C. neoformans from all other yeasts tested and identified the five C. neoformans serotypes. Four major bands of molecular size 800, 540, 475 and 410 bp were recognized for serotypes A, AD and D. Two of them were specific for serotype A and the other two for serotype D isolates. Serotype AD strains were identified by five different genotypic patterns in which at least one of the two bands specific for serotype A and D were present in different combinations. On repeated and simultaneously performed genotype and serotype testing of nine strains, the genotypic pattern did not change, whereas serotyping was unstable in three cases. PCR-fingerprinting using (GACA)4 as a primer proved more stable than serology in discriminating among C. neoformans serotypes A, D and AD and was able to distinguish among serotype AD strains.