Monitoring Neutrophil Recruitment Dynamics and Bacterial Burden at the Infection Site in a Murine Model

To monitor the recruitment of neutrophils — essential immune cells that facilitate bacterial clearance, begin with an anesthetized, transgenic, immunocompromised mouse with a wound exposing the connective tissue on its back.

The transgenic mouse's neutrophils express an enhanced green fluorescent protein, which facilitates neutrophil tracking. Additionally, their impaired bacteria-killing ability makes the mouse more susceptible to infection.

Take a genetically modified bacterial inoculant possessing bioluminescence — light-emitting characteristics.

Inject the bacterial inoculum at the wounded site, ensuring its delivery between the connective tissue and the fascia — a fibrous tissue layer beneath the connective tissue. At the injection site, the bacteria proliferate and colonize, causing tissue infection.

In response to the infection, the immune cells release chemokines — chemical signaling molecules that attract the neutrophils. The neutrophils rapidly migrate via chemotaxis — chemical-induced movement, and extravasate through the blood vessels into the tissue in the vicinity of the bacterial infection.

Image the mouse for bioluminescence and fluorescence signals, representing the bacterial burden and the recruited neutrophils, respectively.

Over time, an increase in the bioluminescence and fluorescence signals correlates with the increased bacterial burden and continual neutrophil recruitment at the infection site.