Serotype, mating type and ploidy of Cryptococcus neoformans strains isolated from AIDS patients in Thailand

Purpose. Serotype, mating type and ploidy are cellular parameters helpful f or understanding the ecology and pathogenic potential of Cryptococcus neofo rmans isolates. In the present study C. neoformans strains isolated from AI DS patients in Thailand were examined for those biological characteristics. Materials and methods. A total of 104 C. neoformans strains were isolated f rom 90 AIDS patients in Khon Kaen, Thailand. Serotypes of these isolates we re determined by an agglutination test with the Crypto Check Iatron. The ma ting tests were performed by crossing with standard alpha- and alpha -matin g type testers. The DNA content of the fungal cells was measured with a flu orescence microscope after staining with the DNA-specific dye, propidium io dide. Results. Among a total of 104 strains tested, 103 were found to be serotype A and only one was serotype AD. Ninety-seven of the 103 serotype A strains were the heterothallic a type (MAT alpha) and the remaining 6 were sexuall y untypable. Most of the MAT alpha strains (89/97) were haploid and the rem aining 8 strains were diploid. Similarly, Eve of the 6 untypable mating str ains were haploid and only one strain was diploid. The one serotype AD stra in was MAT alpha and diploid. There were no alpha -mating type (MAT alpha) strains among the 104 isolates. These results suggest that the serological, sexual and ploidy characteristics in C. neoformans strains isolated from A IDS patients in Thailand were rather simple.