Virulence and antifungal susceptibility of environmental and clinical isolates of Cryptococcus neoformans from Puerto Rico.

Studies on the distribution, epidemiology and pathogenesis of Cryptococcus neoformans on the island of Puerto Rico are few. We have studied mouse virulence and in vitro antifungal susceptibility of 133 isolates of C. neoformans: 121 environmental and 12 clinical (9 from AIDS patients), that were isolated in Puerto Rico. In experimental CD-1 mice infected intravenously, the mean lethal dose 50% values (28 days) were greater than 5.2 x 10(6) and 1.1 x 10(5) cells/mouse for environmental and clinical isolates, respectively. Using an agar dilution assay, the minimum inhibitory concentrations of amphotericin B, ketoconazole and 5-fluorocytosine were comparable for environmental and clinical isolates in both yeast nitrogen dextrose base agar and Kimming's agar. These data suggest a difference in lethality for mice, but no difference in antifungal susceptibility of environmental and clinical isolates of C. neoformans obtained in Puerto Rico.