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The effect of experimental infection with Rhodococcus equi on immunodeficient mice.
J A Yager1, C A Prescott, D P Kramar
1Department of Pathology, Ontario Veterinary College, University of Guelph, Ontario, Canada.
Veterinary Microbiology
|August 30, 1991
Summary
A competent cellular immune system is crucial for clearing Rhodococcus equi and preventing pneumonia. Deficiencies in complement, phagocytic, or NK cells did not impair bacterial clearance in mice.
Area of Science:
- Immunology
- Microbiology
- Pathogenesis
Background:
- Rhodococcus equi causes respiratory disease.
- Understanding its pathogenesis requires studying host immune responses.
Purpose of the Study:
- To investigate Rhodococcus equi pathogenesis by comparing pulmonary clearance in genetically distinct mice with immune deficits.
- To identify the role of specific immune components in controlling R. equi infection.
Main Methods:
- Intranasal inoculation of R. equi in complement-deficient (A/J), immunodeficient (nude, SCID/beige), beige, and normal (SW) mice.
- Assessment of bacterial clearance in lungs, liver, and spleen at multiple time points (days 1, 4, 7, 14).
- Histopathological examination of lung lesions.
Main Results:
- Beige mice showed rapid and complete clearance, indicating phagocytic/NK cell deficits did not impair clearance.
- Nude and SCID/beige mice exhibited impaired clearance, leading to severe pneumonia and systemic bacterial proliferation.
- A/J and SW mice had transient lesions, while nude and SCID/beige mice developed severe bronchopneumonia.
Conclusions:
- Pulmonary clearance of R. equi does not require complement, phagocytic, or NK cells.
- A functional cellular immune system is essential for preventing pneumonia and mortality.
- The capsule of R. equi plays a significant role in its virulence in mice.