Streptococcus pneumoniae infection can cause the formation of microlesions within the heart tissue.
The bacteria within the microlesions produce toxins that inhibit the infiltration of host immune cells inside the microlesion.
To visualize these microlesions, take a euthanized mouse infected with S. pneumoniae.
Disinfect the chest area with ethanol.
Make an incision and transect the diaphragm.
Then cut and lift the rib cage to expose the heart.
Cut the connecting blood vessels and excise the heart.
Wash the heart with a buffer to remove residual blood.
Then, place the heart in a tissue specimen collection cassette and immerse the cassette in a fixative solution to fix the heart tissue.
Obtain a coronal section of the heart and perform hematoxylin and eosin staining to stain the bacteria.
Under a microscope, visualize the microlesion containing stained bacteria.
Harvest the heart. Immobilize the euthanized mouse in a supine position on a surgical platform, and spray the chest with 70% ethanol and pat dry. Using surgical scissors and forceps, open the chest cavity, remove the rib cage, and transect the diaphragm to expose the heart and lungs.
Then, cut the blood vessels connected to the heart and use forceps to gently excise the heart without bruising. Rinse the heart with PBS and place it into a tissue specimen collection Cassette for coronal sectioning. Then transfer the cassettes to 10% buffered formalin solution, and on the following day, send for paraffin embedding.
At early stages, cardiac lesions can be identified by their change in color appearance, and in some instances, the presence of immune cells. In advanced lesions, immune cells will be absent, and large vascular-like lesions are found in their place.
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