Quantifying Bacterial Load in the Mouse Heart Following Tail Vein Injection of Listeria monocytogenes

Take a restrained mouse and clean its tail with alcohol to reduce contamination at the injection site and dilate the vein.

Inject Listeria monocytogenes, a pathogenic bacterium, into the tail vein to deliver it directly into the bloodstream.

Apply gentle pressure at the injection site to stop bleeding, then allow the mouse to recover.

The injected bacteria circulate systemically and reach the heart. They then colonize the heart, establishing an infection.

Later, harvest the pathogen-infected heart from the euthanized mouse.

Homogenize the heart using a homogenizer to release bacteria from the tissue.

Perform serial dilutions of the homogenate in a multi-well plate.

Spot small volumes from each dilution onto an agar plate and allow them to dry.

Incubate the plate to allow the bacteria to proliferate and form visible colonies.

Count the colonies to determine the bacterial load in the infected mouse heart.

To inoculate L. monocytogenes into mice, place one animal into a harness in order to restrain the animal during injection. Use an alcohol pad to clean the injection site and dilate the tail vein.

Then, with a 1 milliliter syringe and a 27.5 gauge needle, gently inject the tail vein of the mous