Members of
Cryptococcus neoformans (
C.n. ) species complex cause life-threatening infections. Its taxonomy is an open question, with 2 anamorph species originally described:
C. neoformans &
C. gattii. Mating experiments linked them to the teleomorph genus
Filobasidiella, establishing 2 varieties:
C.n. var.
neoformans =
F.n. var.
neoformans (serotypes A, D & AD) &
C.n. var.
gattii =
F.n. var.
bacillispora (serotypes B & C).
C.n. var.
grubii, was established as a separate variety causing most infections. Molecular data suggested
C.n. var.
gattii as a new species,
C. bacillisporus, recently renamed as
C. gattii. PCR-fingerprinting, AFLP,
URA5,
PLB1 &
ACT1 RFLP analysis, sequencing (
ITS, URA5, PLB1 &
ACT1) & microsatellite analysis have been used to study the genetic diversity of the
C.n. species complex. PCR-fingerprinting, AFLP & RFLP analysis divided more than 1000 global isolates into 8 molecular types. VNI/AFLP1 & VNII/AFLP1A =
C.n. var.
grubii, serotype A; VNIII/AFLP3 = hybrid between
C.n. var.
grubii &
C.n. var.
neoformans, serotype AD; VNIV/AFLP2 =
C.n. var.
neoformans, serotype D; & VGI/AFLP4, VGII/AFLP6, VGIII/AFLP5 & VGIV/AFLP7 =
C. gattii, serotypes B & C. AD hybrid isolates (VNIII/AFLP3) revealed patterns that correspond to a number of molecular types, suggesting recombination events leading to diploid or aneuploid strains. VNI & VGI are the predominant genotypes worldwide. Similar regional profiles of tree-derived & clinical isolates support an epidemiological link. The Vancouver Island outbreak is caused by the rare genotype VGII/AFLP6, which seems to be emerging in temperate climates (Greece & Colombia). Whole genome sequence analysis of the strains H99 (
C.n. var.
grubii ), B3501 & JEC21 (
C.n. var.
neoformans ) & WM276 (
C. gattii ) has shown different levels of microsatellite abundance & polymorphism per variety/species & large variations in the flanking regions. The genotypic variation found among the 8 molecular types lies within a comparable range of that found in established fungal species, suggesting further speciation of the
C.n. species complex. The specificity of the microsatellite flanking regions to a certain genotype is adding evidence to the existence of separate species.
抄録全体を表示