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About C. neoformans serotype B isolate R265

Cryptococcus neoformans, a ubiquitous human pathogen, is the leading cause of infectious meningitis. The Cryptococcus species have been diverging over the past 40 million years into three distinct varieties and four serotypes: the predominantly opportunistic pathogens C. neoformans var. neoformans (serotype D) and C. neoformans var. grubii (serotype A) and the primary pathogen C. neoformans var. gattii (serotypes B and C). The genome projects at TIGR/Stanford and Broad/Duke are sequencing three strains [serotype A (strain H99), serotype D (JEC21 and B3501 strains)], and the University of British Colombia has produced ~5X coverage sequence for serotype B, Australian environmental strain WM276.

Serotype B isolate R265 caused an outbreak on Vancouver Island in Canada that involved more than 50 infections in otherwise healthy human patients, with at least four fatalities (Fyfe, Black et al. 2002). Intervarietal mating tests revealed that the majority of the Vancouver clinical and environmental outbreak isolates were fertile compared with 100% of the environmental isolates from Australia that were sterile (Fraser, Subaran et al. 2003). The outbreak isolate R265 has a VGII molecular genotype by PCR fingerprinting, which differs from the VGI molecular genotype of strain WM276 (J. Kronstad, personal communication). Many mating-type-locus specific PCR reactions that work with a large variety of gattii isolates (both serotype B and C) do not work on these outbreak isolates (J. Fraser, personal communication). Thus, these data demonstrate sufficient genetic variations between this outbreak strain and the previously sequenced genome.