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Updated: Jun 19, 2026
Following in Real Time the Impact of Pneumococcal Virulence Factors in an Acute Mouse Pneumonia Model Using Bioluminescent Bacteria
Published on: February 23, 2014
PULMONARY EDEMA IN INFLUENZAL PNEUMONIA OF THE MOUSE AND THE RELATION OF FLUID IN THE LUNG TO THE INCEPTION OF
1Department of Medicine and the Oscar Johnson Institute for Medical Research, Washington University School of Medicine, St. Louis.
Abstract:
Pulmonary edema is a component of the fully developed influenza viral lesion in the mouse. Mice with experimental pulmonary fluid have an increased susceptibility to inhaled pneumococci and under these circumstances the organisms grow in the lung and produce the lesion of bacterial pneumonia. The presence of pulmonary edema in the lesion due to the influenza virus in the lung of the mouse appears to account adequately for the previous observation that inhaled pneumococci grow in the influenza viral lesion. Mice dying of pneumococcal septicemia after inhaling fine droplets containing this organism do not have pneumonia. The delay in migration of polymorphonuclear leucocytes into the lung after injection of pneumococci suspended in serum is an important factor in susceptibility to infection since it allows ample time for pneumococci to grow in the pulmonary fluid. The slow phagocytic action of pulmonary macrophages likewise permits growth of pneumococci. Conditions in human beings that are known to be complicated by pulmonary edema are also known to be associated with increased susceptibility to secondary bacterial pneumonia.
Insights
Pulmonary edema, a complication of influenza virus infection in mice, increases susceptibility to secondary bacterial pneumonia. This fluid buildup in the lungs allows inhaled bacteria to grow, leading to severe lung lesions.
Area of Science:
- Pathology
- Microbiology
- Immunology
Background:
- Influenza virus infection in mice leads to pulmonary edema.
- Pulmonary edema is associated with increased susceptibility to secondary bacterial pneumonia in humans.
Purpose of the Study:
- To investigate the role of pulmonary edema in the pathogenesis of secondary bacterial pneumonia following influenza virus infection in mice.
- To understand the mechanisms by which pulmonary edema enhances susceptibility to bacterial growth in the lung.
Main Methods:
- Induction of influenza viral lesions in mice.
- Inhalation exposure to Streptococcus pneumoniae.
- Assessment of bacterial growth, inflammatory cell migration, and phagocytic activity in the lung.
Main Results:
- Mice with influenza-induced pulmonary edema showed increased susceptibility to inhaled pneumococci.
- Pneumococci readily grew in the pulmonary fluid, leading to bacterial pneumonia.
- Delayed polymorphonuclear leukocyte migration and slow macrophage phagocytosis contributed to bacterial proliferation.
Conclusions:
- Pulmonary edema resulting from influenza virus infection in mice adequately explains the enhanced growth of inhaled pneumococci.
- Impaired immune cell function in the edematous lung facilitates secondary bacterial pneumonia.
- Findings in mice correlate with increased risk of secondary bacterial pneumonia in humans with pulmonary edema.
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