[Study on genotype and virulence of Cryptococcus neoformans and Cryptococcus gattii clinical isolates in Guigang, Guangxi Zhuang Autonomous Region].

OBJECTIVE: To understand the species, genotypes and mating types of Cryptococcus neoformans and Cryptococcus gattii isolated from clinical samples in Guigang, Guangxi Zhuang Autonomous Region. METHODS: A total of 20 Cryptococcus strains were isolated from clinical samples in Guigang from 2009 to 2012. The biological identification was conducted by polymerase chain reaction (PCR) to amplify internal transcribed spacer (ITS) sequences. The serotypes and mating types of C. neoformans and C. gattii were identified by PCR with serotype-specific and mating type-specific primers. The genotype was characterized by PCR fingerprinting and URA5 gene restriction fragment length polymorphism (URA5-RFLP). Phenotype study included growth test at 37 °C, melanin production test and urease test. RESULTS: Among the 20 strains, 19 (95%) were identified as C. neoformans varieties (var.) grubii (serotype A, mating type α, genotype VN I), and only 1 was identified as C. gattii (mating type α, genotype VG I). The results of virulence test showed that all the strains grew well at 37 °C and positive in both urease test and melanin production test. CONCLUSION: C. neoformans var. grubii (serotype A, genotype VN I and mating type α) was the predominant pathogen causing cryptococcosis in Guigang, and C. gattii strain was also detected.