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Virulence of six strains of Mycobacterium bovis (BCG) in mice
Abstract:
The abilities of six strains of Mycobacterium bovis strain BCG to replicate in vivo and to cause spleen enlargement in the CDF(1) male mouse were compared. The strains were grown in synthetic medium and harvested soon after complete pellicles were produced on liquid medium. In addition, two freeze-dried commercially available preparations were tested. The comparisons were made on the basis of injecting equal numbers of colony-forming units. Strain differences were marked. The Brazil strain was most effective in stimulating spleen enlargement, and the Japan strain was the least effective. This correlated with the number of colony-forming units isolated from the spleen.
Insights
Different Mycobacterium bovis strain BCG strains show varying abilities to replicate in mice and cause spleen enlargement. The Brazil strain induced the most significant spleen enlargement, while the Japan strain showed the least effect.
Area of Science:
- Immunology
- Microbiology
- Vaccinology
Background:
- Mycobacterium bovis strain bacille Calmette-Guérin (BCG) is widely used as a vaccine against tuberculosis.
- Variations in BCG strain properties can influence vaccine efficacy and host immune response.
- Understanding in vivo replication and immunomodulatory effects of different BCG strains is crucial for vaccine development.
Purpose of the Study:
- To compare the in vivo replication and spleen enlargement potential of six Mycobacterium bovis strain BCG strains in CDF(1) male mice.
- To evaluate the impact of different BCG strains on host immune response, as indicated by spleen size.
- To correlate bacterial load with observed immunological effects.
Main Methods:
- Six Mycobacterium bovis strain BCG strains were cultured in synthetic medium.
- Bacterial cultures were harvested at the pellicle formation stage.
- Equal numbers of colony-forming units (CFUs) of each strain were injected into CDF(1) male mice.
- Spleen enlargement was measured, and CFU counts from spleen tissue were determined.
Main Results:
- Significant differences in spleen enlargement were observed among the tested BCG strains.
- The Brazil strain of BCG induced the most pronounced spleen enlargement.
- The Japan strain of BCG exhibited the least spleen enlargement.
- A positive correlation was found between the number of CFUs isolated from the spleen and the degree of spleen enlargement.
Conclusions:
- Mycobacterium bovis strain BCG strains differ markedly in their ability to replicate in vivo and elicit an immune response in mice.
- The Brazil strain demonstrates a higher capacity for inducing spleen enlargement compared to other strains tested.
- Bacterial load in the spleen is a key factor influencing BCG-induced spleen enlargement.