To inoculate male mice, place two thumb forceps cranially and caudally to the mouse's external genitalia. Retract the prepuce to fully expose the glans penis. Then, once the penis is externally positioned, release the thumb forceps. Reposition the forceps to stabilize the protruding penis perpendicular to the animal, holding the organ gently but tautly. Then, through the small opening in the tip of the urethral meatus, carefully introduce the catheter and gently guide it into the penis using forceps to gently maintain tension.
Once the hub of the catheter meets the tip of the penis, very slowly, dispense 50 microliters of the inoculum while maintaining the position of the penis. Note the quality of the instillation according to a predetermined instillation quality score, such as the one shown here. Retract the catheter slowly over 5 seconds to prevent leakage of the inoculum. Place the mouse in its cage in a supine position. The animal should begin to recover 30 to 45 minutes following administration of the anesthetic.
