ABSTRACT
Objective To investigate the genetic relation between Cryptococcus neoformans var.the clinical strains in MLMT - 13 genotype and the environmental strains in MLMT - 36 genotype. Methods Multilocus microsatellite typing (MLMT) method was applied for the genotype analysis in our study.Through this method, we recognized two genotypes that distinguish a majority of clinical and environmental strains. In order to compare virulence between the two types, we chose to infect BALB/c mice (6 weeks,female) with 9 MLMT-13 strains and 10 MLMT-36 strains intravenously. Results Forty( 17 clinical and 23 environmental isolates) were analyzed. Of 17 clinical strains, 9 belonged to a major type of MLMT-13 (52.9%). They were mainly isolated from clinical specimens. About 43.5% of strains from the environment belong to a major type of MLMT-36, which are indigenous to environments and which were not isolated from clinical samples. The mortality rate and pathological changes of the above mice were observed during two months after injection. The results showed that the mortality rate of mice infected with MLMT-13 strains was 100%, while the mortality rate with MLMT-36 strains was 7. 5%. The pathological sections showed that lesions of MLMT-13 infected mice appeared in the brain, lungs, liver and kidneys, while the lesions of MLMT-36 infected mice only appeared in the brain. Most brains of MLMT-13 infected mice were distorted,and both the number and size of lesions in such brains were much larger than those of MLMT-36 infected mice. Conclusion Our study illustrated the virulent difference between MLMT-13 and MLMT-36, which are isolated from patients and environment respectively. The results inferred that some genetic changes, such ss microsatellite repeats, might occur between environmental and clinical isolates through their environmental adaptation progress.