Evaluation and comparison of the growth and viability of yeast-like cells of Paracoccidioides brasiliensis.

The growth and viability of two Paracoccidioides brasiliensis strains were evaluated in PYG and MMcM media containing no boric acid. The two P. brasiliensis strains exhibited a similar growth pattern in PYG medium, which was considered to be good compared with the growth curves in defined MMcM medium without boric acid. Calculation of cell generation time in the media studied demonstrated that the cells had greater difficulty in forming new generations in MMcM medium containing no boric acid. The present data confirm the literature view that PYG medium is the most complete in terms of nutritive substances for the growth and development of P. brasiliensis.

Inoculation experimental animals with Paracoccidioides brasiliensis strains: an attempt to reestablish the dimorphic process and variation in pathogenicity as a function of time of preservation under mineral oil.

In an attempt to reestablish the dimorphic process in strains of Paracoccidioides brasiliensis in the transition phase (Y reversible M) and to reisolate them, five strains in the transitional phase due to the long time of preservation under mineral oil and two strains in the yeast-like phase were inoculated into male albino rats. The animals were then studied for the presence of paracoccidioidomycotic granulomata. Of the seven strains inoculated, five caused granulomatous nodules in several organs of the animals and only two of these five strains, which had been preserved for the shortest period of time (9 years) were reisolated in culture. Two strains were unable to provoke infection, with no lesions detected in any organ. It is assumed that the long period of time during which the strains were left under oil favored the alteration of celt wall contents, leading to differences in pathogenicity.

Paracoccidioidomycosis in nude mice: presence of filamentous forms of the fungus.

Congenitally athymic nude mice (nu/nu) and their phenotypically normal littermates (nu/+) were intraperitoneally infected with yeast cells of a strain of Paracoccidioides brasiliensis. The nude mice developed a severe and generalized infection with an intense parasitism of several organs, accompanied by a low-grade of tissue reaction. The lesions were characterized by abundant yeast-like cells of the fungus, and in some animals, numerous hyphal forms could be well visualized. In control animals, infection was moderate, almost exclusively restricted to the area of inoculation, and the lesions presented few parasites surrounded by an inflammatory response. Filamentous forms of the fungus were never encountered in these animals.