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Pathogenicity and virulence of wild-type and melanin-deficient Wangiella dermatitidis
Abstract:
Wild-type, dematiaceous Wangiella dermatitidis (DMD 368) and melanin-deficient mutant (Mel 3) strains derived therefrom were compared for pathogenic and virulent effects in Swiss albino mice following intravenous infection. Parameters examined were mouse survival and central nervous system signs of infection, time-course cultures of fungus from brains, lungs, livers, spleens and kidneys, and histopathology of brains. Over a range of concentrations, DMD 368 produced 100% mortality while one Mel 3 strain, DMD 369, produced no mortality by 21 days after inoculation. However, in chronic infections with DMD 369, mice developed ataxia and torticollis. These signs of disease were indistinguishable from those produced by low concentrations of DMD 368. The brain was the most severely affected organ where both DMD 368 and 369 grew exponentially. Histological responses to the two strains appeared to be indistinguishable. However, the mutant appeared not to form the invasive hyphal forms of growth associated with the acute, fatal infections caused by the wild type. Thus, although the absence of melanin was associated with decreased mortality in mice, the chronic neurological signs of mouse phaeohyphomycosis appeared to be unrelated to melanin.
Insights
Wild-type Wangiella dermatitidis caused high mortality in mice, while a melanin-deficient mutant showed reduced deaths but still caused chronic neurological disease. Melanin absence impacts virulence but not chronic phaeohyphomycosis signs.
Area of Science:
- Mycology
- Infectious Diseases
- Pathogenesis
Background:
- Wangiella dermatitidis is a dematiaceous fungus causing phaeohyphomycosis.
- Melanin production is a key virulence factor in many fungal pathogens.
- The role of melanin in W. dermatitidis pathogenesis remains incompletely understood.
Purpose of the Study:
- To compare the pathogenic and virulent effects of wild-type and melanin-deficient Wangiella dermatitidis strains.
- To investigate the role of melanin in W. dermatitidis-induced central nervous system infections in a murine model.
Main Methods:
- Intravenous infection of Swiss albino mice with wild-type (DMD 368) and melanin-deficient mutant (DMD 369) W. dermatitidis strains.
- Monitoring of mouse survival, neurological signs, fungal burden in organs (brain, lungs, liver, spleen, kidneys), and brain histopathology.
Main Results:
- Wild-type W. dermatitidis (DMD 368) caused 100% mortality, whereas the melanin-deficient mutant (DMD 369) showed no mortality within 21 days.
- Chronic infection with the mutant strain led to neurological signs (ataxia, torticollis) similar to those caused by low doses of the wild-type.
- The brain was severely affected by both strains, with exponential fungal growth observed. The mutant did not form invasive hyphae seen in acute infections.
Conclusions:
- Melanin deficiency in W. dermatitidis is associated with decreased acute mortality in mice.
- Chronic neurological signs of phaeohyphomycosis in mice appear independent of melanin production.
- Melanin may play a role in the invasive growth patterns of W. dermatitidis during acute infections.