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Effects of intranasal challenge with group A beta haemolytic streptococcus M type 49 in Swiss albino mice
J Stephen1, A Kuruvilla, S Chandi
1Department of Zoology, Voorhees College, Vellore, India.
Abstract:
Mice are susceptible to natural infections with streptococci and therefore can serve as suitable animal models to study experimental streptococcal infections. In an earlier study, we had shown the development of pharyngeal colonization, antibody response and histopathological changes in the heart following intranasal (IN) challenge with a rheumatogenic serotype of group A beta haemolytic streptococcus, the M type 18. To determine if nonpharyngitis associated serotypes can also elicit similar responses, 30 Swiss albino mice were challenged intranasally with 2 x 10(7) colony forming units of a skin associated serotype of group A beta haemolytic streptococcus, the M type 49. Pharyngeal colonization varied from 64% (n = 30) in the first week to 69% (n = 16) during the fourth week after IN challenge. Eleven (36.7%) of the 30 animals studied showed antibody response to DNase B (ADNB) with peak titers varying from 150 to 1200 units. Wide variations were seen in ADNB titers in individual mice. Histopathological evidence for cardiac lesions were seen in three animals. The changes were mild and varied from mild to chronic endocardial inflammation to calcification. The study shows that Swiss albino mice are also susceptible to IN challenge with skin associated strains of GABHS and therefore can serve as useful models to study the effects of experimental infection with diverse serotypes of GABHS.
Insights
Swiss albino mice effectively model Group A beta-hemolytic streptococcus (GABHS) infections. Intranasal challenge with skin-associated GABHS strains induced pharyngeal colonization, antibody response, and mild cardiac lesions in mice.
Area of Science:
- Microbiology
- Immunology
- Pathology
Background:
- Mice are susceptible to streptococcal infections, making them valuable models for experimental studies.
- Previous research demonstrated pharyngeal colonization, antibody response, and cardiac histopathology after intranasal challenge with a rheumatogenic Group A beta-hemolytic streptococcus (GABHS) M type 18.
Purpose of the Study:
- To investigate if non-pharyngitis associated GABHS serotypes can elicit similar responses in mice.
- To evaluate the susceptibility of Swiss albino mice to intranasal challenge with a skin-associated GABHS serotype (M type 49).
Main Methods:
- Thirty Swiss albino mice were intranasally challenged with 2 x 10^7 colony-forming units of GABHS M type 49.
- Pharyngeal colonization was assessed weekly.
- Antibody response to DNase B (ADNB) was measured.
- Cardiac tissues were examined for histopathological changes.
Main Results:
- Pharyngeal colonization ranged from 64% to 69% throughout the four-week study period.
- Eleven mice (36.7%) developed an antibody response to DNase B (ADNB), with titers varying from 150 to 1200 units.
- Three mice exhibited mild cardiac lesions, including endocardial inflammation and calcification.
Conclusions:
- Swiss albino mice are susceptible to intranasal challenge with skin-associated GABHS strains.
- Mice serve as a useful model for studying experimental infections with diverse GABHS serotypes.
- This model can aid in understanding the pathogenesis of GABHS infections beyond pharyngeal involvement.