Assessing Intracellular Bacterial Persistence and Antibiotic Resistance in a Mouse Model

Take two groups of euthanized mice with exposed abdominal cavities.

The control group is pre-injected with macrophages infected with methicillin-resistant S. aureus.

The treated group is pre-injected with macrophages carrying the same bacteria and the antibiotic gentamicin.

In both groups, bacteria persist, replicate, and evade host immune responses inside macrophage phagosomes. In the treated group, bacteria also resist the antibiotics and remain viable.

Locate the kidneys, which contain the infected macrophages. Carefully detach the kidneys from the surrounding tissue.

Place each kidney in grinding tubes with buffer to preserve bacterial viability.

Homogenize the tissue to lyse macrophages and release intracellular bacteria.

Transfer the homogenate to tubes and prepare serial dilutions in buffer.

Spot each dilution onto nutrient-rich agar plates.

Incubate until visible colony-forming units (CFUs) develop.

Similar CFUs in both groups indicate gentamicin resistance and intracellular persistence of methicillin-resistant S. aureus within the host.

Place the mouse under an infrared physiotherapy lamp until the tail vein is dilated. Randomly divide the mice into four groups. Intravenously inject