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Streptococcus pyogenes infection in mice
L K Husmann1, D L Dillehay, V M Jennings
1Department of Microbiology and Immunology, Emory University, Atlanta, GA 30322, USA.
Abstract:
We inoculated 5 to 7-week-old female C3HeB/FeJ mice with Streptococcus pyogenes strain B514-Sm (type M50) by both an intranasal and intratracheal route and characterized the resulting illness. Following intranasal inoculation, the animals developed signs of illness within 1 to 8 days post-inoculation which correlated with acute, suppurative, bronchopneumonia during histopathologic analysis; however, the relationship of response to dose was non-linear, as seen previously in a small group of mice. Intratracheal inoculations were then performed to increase the quantitative reliability of the model. Following intratracheal inoculation, the animals succumbed to an illness that was indistinguishable from that seen after intranasal inoculation, and the incidence of pneumonia followed a steep dose response curve. The dose at which 50% of the animals exhibited signs of respiratory illness within 72 h was 1.0 x 10(7) colony forming units. All of the animals that appeared ill had lung lesions as determined by gross and histopathologic examination. Bacteraemia followed pneumonia in two-thirds of the intratracheally inoculated animals, indicating that the S. pyogenes had crossed tissue barriers. We hope that this model will be useful in future studies concerning the role of suspected streptococcal virulence factors in the later stages of pathogenesis of invasive S. pyogenes infection.
Insights
This study developed a mouse model for invasive Streptococcus pyogenes infection. Intratracheal inoculation effectively induced pneumonia and bacteremia, establishing a reliable model for studying streptococcal pathogenesis.
Area of Science:
- Microbiology
- Pathogenesis
- Infectious Disease
Background:
- Streptococcus pyogenes is a significant human pathogen.
- Invasive infections require robust animal models to study pathogenesis.
Purpose of the Study:
- To establish and characterize a reproducible mouse model for invasive Streptococcus pyogenes infection.
- To investigate the dose-response relationship of S. pyogenes inoculation via intranasal and intratracheal routes.
Main Methods:
- Female C3HeB/FeJ mice were inoculated with Streptococcus pyogenes strain B514-Sm (type M50) via intranasal and intratracheal routes.
- Dose-response effects and resulting pathology, including pneumonia and bacteremia, were assessed.
- Histopathological analysis was used to evaluate lung lesions.
Main Results:
- Intratracheal inoculation led to dose-dependent bronchopneumonia and signs of illness.
- A dose of 1.0 x 10(7) colony-forming units (CFUs) caused respiratory illness in 50% of mice within 72 hours.
- Bacteremia occurred in two-thirds of intratracheally inoculated mice, indicating systemic spread.
Conclusions:
- Intratracheal inoculation provides a quantitative and reliable method for modeling invasive S. pyogenes infection in mice.
- This model is suitable for future research on streptococcal virulence factors and invasive disease pathogenesis.
