Virulence of Paracoccidiodes brasiliensis: the influence of in vitro passage and storage
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E Brummer1, A Restrepo, L H Hanson
1Department of Medicine, Santa Clara Valley Medical Center, San Jose, CA 95128.
Abstract:
Stability of virulence in P. brasiliensis isolates was studied with respect to the in vitro culture history and methods used for storage. Virulence in yeast-form P. brasiliensis isolates was tested in a chronic pulmonary murine model of paracoccidiodomycosis where progression of disease was quantitated in terms of colony forming units recoverable from lungs. Four isolates of P. brasiliensis, including recently isolated form patients or experimental animals, caused chronic progressive disease. Two isolates with a history of subculturing showed attenuation by causing resolving but chronic disease. An attenuated isolate became avirulent subsequent to 15 more years of subculturing. These findings suggest that virulence of P. brasiliensis can be attenuated or lost subsequent to cycles of subculturing over long periods. Our data suggest that the use of fresh P. brasiliensis isolates may be needed to provide reproducible virulence for experimental systems.
Insights
Paracoccidioides brasiliensis virulence can decrease with prolonged in vitro culturing. Freshly isolated P. brasiliensis strains are recommended for reproducible experimental models of paracoccidioidomycosis.
Area of Science:
- Mycology
- Infectious Diseases
- Pathogen Virulence
Background:
- Paracoccidioides brasiliensis (P. brasiliensis) is a fungal pathogen causing paracoccidioidomycosis.
- Understanding factors affecting P. brasiliensis virulence is crucial for disease modeling.
Purpose of the Study:
- To investigate the stability of P. brasiliensis virulence.
- To determine the impact of in vitro culture history and storage on virulence.
Main Methods:
- Yeast-form P. brasiliensis isolates were tested for virulence in a chronic pulmonary murine model.
- Disease progression was quantified using colony-forming units (CFUs) in lungs.
Main Results:
- Four recently isolated P. brasiliensis strains caused progressive disease.
- Two isolates with subculturing history showed attenuated virulence, leading to resolving chronic disease.
- One attenuated isolate became avirulent after 15 additional years of subculturing.
Conclusions:
- Prolonged subculturing can attenuate or lead to loss of P. brasiliensis virulence.
- Freshly isolated P. brasiliensis strains are essential for reproducible experimental virulence studies.