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PATHOGENESIS OF PNEUMOCOCCUS INFECTIONS IN MICE
1Laboratories of The Rockefeller Institute for Medical Research.
Abstract:
Unprepared mice given intranasal inoculations of certain strains of pneumococci develop pneumonia. The proportion of inoculated mice which will show the pneumonia at autopsy is dependent upon the strain and type of organism and the breed of mice used. It has been shown that, with the technique employed, the pneumococci reach the lower respiratory tract and alveoli almost immediately; moreover, that an invasion of the blood stream occurs very rapidly and can be demonstrated in a third of mice during the first 10 minutes. There is some evidence that invasion of the tissues and the blood stream may occur both through the upper respiratory tract, probably the nasal mucosa, and through the alveolar walls. It is uncertain which route of invasion, if either, is of the most importance. It has been possible to produce pneumonia by direct intravenous inoculation of pneumococci. It may be that the pneumonia is favored by a reaction at the point of invasion through the alveolar walls in the intranasally inoculated mice, but the results of the intravenous inoculation make it clear that such a local lesion is unnecessary for the production of pneumonia in mice.
Insights
Intranasal inoculation of pneumococci in mice causes pneumonia, with infection rapidly spreading to the bloodstream. This study investigates the routes of bacterial invasion and pneumonia development in mice.
Area of Science:
- Microbiology
- Pathology
- Immunology
Background:
- Pneumonia is a significant respiratory illness.
- Bacterial pneumonia can be caused by Streptococcus pneumoniae (pneumococci).
- Understanding infection pathways is crucial for developing treatments.
Purpose of the Study:
- To investigate the development of pneumonia in mice following pneumococcal inoculation.
- To determine the routes of bacterial invasion and their role in pneumonia pathogenesis.
- To explore the necessity of a local lesion for pneumonia development.
Main Methods:
- Intranasal inoculation of mice with specific pneumococcal strains.
- Autopsy to assess pneumonia incidence.
- Intravenous inoculation to compare infection routes.
- Bloodstream invasion assessment within the first 10 minutes post-inoculation.
Main Results:
- Intranasal pneumococcal inoculation successfully induced pneumonia in mice.
- Pneumonia incidence varied based on pneumococcal strain, type, and mouse breed.
- Rapid bloodstream invasion occurred, detectable within 10 minutes.
- Pneumonia could be induced via intravenous inoculation, indicating a local lesion is not essential.
Conclusions:
- Pneumococci rapidly reach the lower respiratory tract and bloodstream after intranasal inoculation.
- Both upper respiratory tract and alveolar routes may contribute to bacterial invasion.
- Pneumonia in mice does not require a localized inflammatory response at the site of initial bacterial entry.
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