Abstract
The effects of storage with programmed freezing on the virulence and morphology of Paracoccidioides brasiliensis were analyzed by using yeast form cells of 3 strains (Bt-9, Pb-18 and B-1183). From each original strain (O: Original), the following three subcultures were prepared: Subculture F, frozen at -135°C for 6 month; subculture OA, original strain through a mouse; and subculture FA, the frozen strain through a mouse. The virulence and morphology of these subcultures were compared with those of the original strains. Amounts of 106 colony forming units of yeast form cells of each strain were inoculated intravenously into young adult male ddY mice. The virulence of the original strain Bt-9 weakened after the storage at -135°C and did not recover even after animal passage. The morphology was also different from that of the original strain. However, the virulence of strains Pb-18 and B-1183 was not weakened by being frozen and stored at that temperature nor was their morphology change. Storage at -135°C with programmed freezing thus seems inappropriate for P. brasiliensis yeast form cells.
