Related Experiment Video
Updated: Aug 18, 2026
Toxoplasma gondii Cyst Wall Formation in Activated Bone Marrow-derived Macrophages and Bradyzoite Conditions
Published on: August 12, 2010
Paracoccidioides brasiliensis: virulence and an attempt to induce the dimorphic process with fetal calf serum
C De Moraes Borba1, G M V Schäffer
1Departamento de Micologia, Instituto Oswaldo Cruz, Fundação Oswaldo Cruz, FIOCRUZ, Rio de Janeiro, RJ, Brazil. cborba@gene.dbbm.fiocruz.br
Abstract:
The virulence of Paracoccidioides brasiliensis strains and the induction of the dimorphic process of the fungus were investigated. The strains were kept under mineral oil for different periods of time, except for one that was successively subcultured on agar slants. Four strains with transitional morphology at room temperature were avirulent to experimental animals. Two strains with typical morphology at 36 degrees C, one of them preserved under mineral oil for 16 years and the other maintained by successive subcultures for 10 years, were virulent to mice. These strains caused macro- and microscopic lesions in various organs, with enlargement of the spleen and heart. An attempt to induce the dimorphic process with fetal calf serum (FCS) in P.brasiliensis strains with transitional morphology failed. FCS was probably unable to stimulate the synthesis of Y cell wall alpha-1,3-glucan. The results demonstrate that keeping strains under mineral oil for a long period of time may have altered the enzymatic activities of the proteinases and other virulence factors that participate in the transition process and in pathogenesis.
Insights
Long-term storage of Paracoccidioides brasiliensis under mineral oil may reduce its virulence by altering key enzymes. This impacts the fungus
Area of Science:
- Mycology
- Infectious Diseases
- Pathogenesis Research
Background:
- Paracoccidioides brasiliensis is a fungus causing paracoccidioidomycosis.
- Fungal virulence and dimorphism are critical for pathogenesis.
- Strain preservation methods can influence fungal characteristics.
Purpose of the Study:
- To investigate the virulence of P. brasiliensis strains.
- To examine the induction of the fungus' dimorphic process.
- To assess the impact of preservation methods on virulence and dimorphism.
Main Methods:
- Comparison of P. brasiliensis strains preserved under mineral oil versus successive subculturing.
- Assessment of fungal morphology at room temperature and 36°C.
- Evaluation of virulence in experimental animals (mice).
- Attempted induction of dimorphism using fetal calf serum (FCS).
Main Results:
- Strains with transitional morphology at room temperature were avirulent.
- Strains with typical morphology at 36°C, including those preserved for 16 years under mineral oil, were virulent.
- Virulent strains induced significant lesions in mice.
- FCS failed to induce dimorphism in transitional strains, suggesting impaired alpha-1,3-glucan synthesis.
Conclusions:
- Long-term mineral oil preservation may attenuate P. brasiliensis virulence.
- Alterations in proteinase activity and other virulence factors are likely.
- Preservation methods significantly affect fungal virulence and dimorphic transition.
