Presence of alpha and a mating types in environmental and clinical collections of Cryptococcus neoformans var. gattii strains from Australia

Cryptococcus neoformans var. gattii lives in association with certain speci es of eucalyptus bees and is a causative agent of cryptococcosis. It exists as two mating types, MAT alpha and MATa, which is determined by a single-l ocus, two-allele system. In the closely related C. neoformans var. neoforma ns, the alpha mating type has been found to outnumber its a counterpart by at least 30:1, but there have been very limited data on the proportions of each mating type in C, neoformans var. gattii. In the present study, specif ic PCR primers were designed to amplify two separate alpha-mating-type gene s from C. neoformans var. gattii strains. These mere used to survey for the presence of the two mating types in clinical and environmental collections of C neoformans var. gattii strains from Australia. Sixty-eight of 69 clin ical isolates produced both or mating type-specific bands and were assumed to be of the alpha mating type. The majority of environmental isolates were also of the or mating type, but the a mating type was located in two separ ate areas, In one area, the alpha mating type outnumbered the alpha mating type by 27:2, but in the second area, the ratio of the two mating types was close to the 50:50 ratio expected for sexual recombination.