Establishment of a Urinary Tract Infection Model in Female Mice

Begin with an anesthetized female mouse in a supine position and empty its bladder.

Take a pre-assembled syringe with an attached catheter containing a suspension of uropathogenic  Escherichia coli bacteria.

Insert the catheter through the urethral orifice into the bladder and slowly deliver the bacterial suspension.

Post-injection, recover the mouse in a supine position.

The fimbriae of bacteria bind to specific receptors on bladder epithelial cells, triggering their internalization within the underlying epithelial cells.

Inside bladder epithelial cells, bacteria multiply, with some adopting a filamentous morphology, and form dense intracellular bacterial communities or IBCs.

These IBCs exhibit biofilm-like properties, protecting the bacteria from the mouse's immune defense system and contributing to persistent infection.

Over time, IBCs rupture, releasing bacteria into the bladder lumen; the bacteria possessing the filamentous morphology adhere to neighboring epithelial cells.

This leads to the spreading of infection, establishing a urinary tract infection in the female mouse.

After anesthetizing a female mouse, according to an approved protocol, place the animal supine, and apply medium pressure to the lower abdomen to empty the bladder of urine. Full bladders feel like a pea under the skin between the iliac crests.

When the bladder is empty, using the non-dominant hand, place the thumb on the tail and a finger of the same hand on the abdomen of the mouse, and apply gentle pressure in opposing directions to hold the mouse firmly in place. Next, place the tip of the catheter perpendicular to the mouse at the urethral orifice. Then, with gentle pressure, slide the catheter into the urethra until the hub meets the urethral orifice while simultaneously lowering the syringe so that it is parallel to the working surface.

Once the catheter is in place, use a finger from the non-dominant hand that's resting on the mouse's abdomen to very gently pull the abdominal skin towards the head of the mouse. Note that the urethral orifice will not move. However, if the catheter is in the vagina, the tissue will move up and away from the catheter. With the hub of the catheter against the urethral orifice, slowly dispense 50 microliters of the bacterial inoculum.

A slow installation rate minimizes vesicoureteral reflux into the kidney. Slowly remove the catheter to prevent leakage, then, place the animal in its cage in a supine position.