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Pathogenicity of some ordinarily harmless yeasts for cortisone-treated mice
Abstract:
The pathogenicity for normal and cortisone-treated mice of Candida requinyii, Pichia etchellsii, Candida famata (Torulopsis candida) Trichosporon cutaneum and Sterigmatomyces aphidis, isolated from foodstuffs or clinical material, is reported. The test species proved nonpathogenic to normal mice inoculated intravenously with up to 10(7) cells. There was neither any mortality nor gross or microscopic lesions, and cultures were negative from the visceral organs and brain when these animals were necropsied after 3 weeks of observation. In cortisone-treated mice, on the other hand, the yeasts caused mortalities, the extent of which varied according to the infecting species and the challenge dose. Candida requinyii was the most pathogenic species, causing 100% mortality in 8 days, followed by S. aphidis, C. famata, T. cutaneum and P. etchellsii which killed 75%, 50%, 38% and 25% of the infected animals. Apart from the higher mortalities, C. requinyii and S. aphidis caused more frequent visceral lesions than did either T. cutaneum or C. famata. Involvement of the brain occurred more commonly with C. requinyii and T. cutaneum than with C. famata or S. aphidis. P. etchellsii was the only yeast that failed to incite any gross or microscopic lesions. The study re-emphasizes the pathogenic potential of ordinarily harmless fungi for immunosuppressed hosts.
Insights
Certain yeasts, typically harmless, can become pathogenic in immunosuppressed hosts. Cortisone treatment in mice revealed varying levels of virulence among Candida requinyii, Pichia etchellsii, Candida famata, Trichosporon cutaneum, and Sterigmatomyces aphidis.
Area of Science:
- Mycology
- Immunology
- Infectious Diseases
Background:
- Yeasts like Candida famata and Trichosporon cutaneum are often found in food and clinical settings.
- Their pathogenicity in hosts with compromised immune systems is a significant concern.
Purpose of the Study:
- To evaluate the pathogenicity of five yeast species in normal and cortisone-treated mice.
- To determine the virulence differences among Candida requinyii, Pichia etchellsii, Candida famata, Trichosporon cutaneum, and Sterigmatomyces aphidis.
Main Methods:
- Intravenous inoculation of yeast cells (up to 10^7) into normal and cortisone-treated mice.
- Observation for mortality, gross and microscopic lesions, and organ cultures over 3 weeks.
- Comparative analysis of pathogenicity based on species and challenge dose.
Main Results:
- All tested yeasts were nonpathogenic in normal mice.
- Cortisone treatment rendered mice susceptible, with varying mortality rates: Candida requinyii (100%), S. aphidis (75%), C. famata (50%), T. cutaneum (38%), and P. etchellsii (25%).
- Candida requinyii and S. aphidis caused more frequent visceral and brain lesions compared to other species.
Conclusions:
- The study highlights the opportunistic nature of these yeasts, emphasizing their pathogenic potential in immunosuppressed individuals.
- Immune status is a critical factor in determining the virulence of these fungi.
- Findings underscore the importance of considering host immunity when assessing fungal infection risks.