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Oxygen uptake and lung function in mice infected with Streptococcus pneumoniae, influenza virus, or Mycoplasma
Abstract:
Model systems of respiratory infection in mice were established with Streptococcus pneumoniae, influenza virus, and Mycoplasma pulmonis. The LT50 for S. pneumoniae was 2 1/2 days, for lethal influenza 6 days, and for M. pulmonis 5 days. Morbidity in sublethal influenza infections reached a peak during days 5 to 10, with recovery indicated by the third week. The course of each pulmonary infection was followed by use of the animal's maximal ability to consume oxygen (VO2max by determining the weight, compliance, and stability of the excised lung, and in some cases by following O2 consumption of minced tissue. Depression of VO2max began early in each infection; reductions ranged from 9% at the peak of sublethal influenza infection to 50% 12 to 48 hr before the LT50 of fatal infections. The depressions were not relieved by 100% O2. The noninvasive VO2max test, evoked by cold air, was simple, rapid, and reproducible and appeared to serve as a quantitative measure of over-all function during infection. Each type of infection caused an increase in lung weight, with the largest noted during fatal Mycoplasma illness and lethal influenza. The effects on lungs by influenza and M. pulmonis infections were similar but could be differentiated from those with S. pneumoniae. With sublethal influenza, CL was reduced 30% between days 5 to 10, with recovery by the third week. Ctis was not affected. M. pulmonis infections and lethal influenza caused depressions in CL of over 60% by day 4 but only a 30% decrease in Ctis. The data suggest that the decreased compliance in influenza and M. pulmonis infections was due primarily to increased surface tension. In contrast, S. pneumoniae did not affect compliance.
Insights
This study shows that maximal oxygen consumption (VO2max) is a sensitive indicator of respiratory infection severity in mice. Different pathogens like influenza and Mycoplasma pulmonis significantly impact lung function, unlike Streptococcus pneumoniae.
Area of Science:
- Respiratory Medicine
- Infectious Diseases
- Animal Models
Background:
- Respiratory infections pose significant health challenges.
- Accurate assessment of lung function during infection is crucial for understanding disease progression.
- Mouse models are valuable for studying pulmonary pathogens.
Purpose of the Study:
- To evaluate the maximal oxygen consumption (VO2max) test as a noninvasive measure of respiratory infection severity in mice.
- To compare the effects of Streptococcus pneumoniae, influenza virus, and Mycoplasma pulmonis on lung function.
- To investigate the relationship between VO2max, lung mechanics, and pathogen-specific infection models.
Main Methods:
- Established mouse models for Streptococcus pneumoniae, influenza virus, and Mycoplasma pulmonis infections.
- Measured maximal oxygen consumption (VO2max) using a cold air challenge.
- Assessed lung weight, compliance (CL), and stability (Ctis) of excised lungs.
- Monitored animal survival (LT50) and morbidity.
Main Results:
- VO2max depression correlated with infection severity, decreasing significantly before lethal outcomes.
- Influenza and M. pulmonis infections increased lung weight and decreased CL, suggesting increased surface tension.
- S. pneumoniae infection did not significantly affect lung compliance.
- The VO2max test proved to be a rapid, reproducible, and quantitative measure of overall lung function during infection.
Conclusions:
- The VO2max test is a valuable noninvasive tool for assessing the severity of respiratory infections in animal models.
- Influenza and M. pulmonis infections impair lung mechanics primarily through increased surface tension.
- Distinct pathogen-induced lung injury patterns can be differentiated using functional and mechanical assessments.