Related Experiment Videos
Factors determining the susceptibility of mice to experimental phycomycosis
Abstract:
Various factors influencing the susceptibility of C3H mice to lethal infection by the phycomycete Absidia ramosa were examined. Mice 19-21 days old were exposed to graded doses of A. ramosa spores by various routes. After intravenous inoculation with doses in excess of 10(3) viable units, a variable proportion of mice developed lethal phycomycosis of the central nervous system within 2-8 days. The proportion of mice affected was related to the inoculum size, doses of 5 X 10(7) spores producing lethal infection in 90-100% of the mice. The disease was characterised by signs of involvement of the central nervous system appearing 8-12 h before death. At necropsy, fungal hyphae, frequently surrounded by infiltrations of mononuclear cells, could be demonstrated in the brain. Lesions were also often present in the kidneys; in other organs they were rare, but the presence of viable fungal spores could be detected by cultural procedures. Subcutaneous inoculation of A. ramosa spores did not produce lethal infection but intraperitoneal inoculation occasionally did so. Direct intracerebral inoculation invariably produced lethal infection even with very small doses of spores. The clinical and histopathological features of the disease were almost identical with those resulting from intravenous inoculation. Pre-inoculation treatment with azathioprine, cyclophosphamide and antithymocyte serum did not increase susceptibility. Susceptibility was increased by injections of zymosan, aggregared gamma-globulin, cortisone acetate and Fe(II) salts and by reticuloendothelial blockade. These treatments increased the proportion of mice developing lethal phycomycosis of the central nervous system, and in the case of cortisone acetate, also promoted disseminated infection. It was concluded that the natural resistance of mice to A. ramosa infection was probably dependent upon the activity of phagocytic cells, possibly acting in conjunction with complement and other non-specific serum factors.
Insights
This study investigated factors affecting C3H mouse susceptibility to Absidia ramosa infection. Phagocytic cell activity, possibly with serum factors, appears crucial for natural resistance against this fungal pathogen.
Area of Science:
- Mycology
- Immunology
- Infectious Diseases
Background:
- Absidia ramosa is a phycomycete fungus capable of causing opportunistic infections.
- Understanding host susceptibility factors is crucial for managing fungal diseases.
Purpose of the Study:
- To identify factors influencing C3H mouse susceptibility to lethal Absidia ramosa infection.
- To elucidate the role of the immune system in resistance to phycomycosis.
Main Methods:
- C3H mice were inoculated with varying doses of A. ramosa spores via different routes (intravenous, subcutaneous, intraperitoneal, intracerebral).
- Mice were pre-treated with immunosuppressive agents or substances known to modulate immune responses.
- Clinical signs, mortality, and histopathological findings were assessed.
Main Results:
- Intravenous inoculation with >10^3 spores led to lethal central nervous system phycomycosis, dose-dependently.
- Direct intracerebral inoculation invariably caused lethal infection.
- Pre-treatment with azathioprine, cyclophosphamide, or antithymocyte serum did not increase susceptibility.
- Zymosan, aggregated gamma-globulin, cortisone acetate, Fe(II) salts, and reticuloendothelial blockade increased susceptibility and mortality.
Conclusions:
- Natural resistance in mice to A. ramosa likely involves phagocytic cell activity.
- Non-specific serum factors, potentially including complement, may also contribute to host defense.
- Certain immune-modulating treatments can significantly increase susceptibility to A. ramosa infection.