[An urease negative Cryptococcus neoformans].

We report an urease negative Cryptococcus neoformans derived from pigeon dropping. This isolate produced brown pigmented colonies on cornmeal Tween-80 agar with 300 micrograms/ml caffeic acid, but was failure to hydrolyze urea. More identification tests were performed for this isolate, such as assimilation and fermentation of carbohydrates, nitrate assimilation, production of starch like compound, growth on GCP medium, germ tube formation and inoculation of mice, ect. Most of the results showed that the microbiological characteristics of the isolate were typical of C. neoformans except for negative urease test. Even though there has been a report about an urease negative C. neoformans derived from an AIDS patient, but we have never found any report about isolation from pigeon dropping or nature environment. We should pay attention to the exist of this atypical strain of C. neoformans in nature environment and the possibility of infection to human being. Additionally, we also be aware of the possibility of neglect when this urease negative C. neoformans is identified with urease test.