Yes but. . Antibiotics only fight infection. They do nothing to fix a bedsore. When a sick or frail patient lays in one position for a long time and cannot move the pressure over bony prominences ( hip, tailbone, etc ) can crush and kill the skin in between the bone and the bed. Bad ones can even kill off the muscle. If this is infected abx will fight the infection. But if not there is no point in giving .
Depends. Sometimes the skin around an ulcer may be infected and require antibiotics. Also, if the bone is infected then antibiotics are definitely necessary. Sometimes the bone has to be debrided (portions removed) in order to clear the infection.
Bedsore. A pressure ulcer is due to pressure and relief of pressure is the primary focus. Any wound can be expected to have bacteria present in the wound bed but it does not mean there is an infection. This is a clinical impression that is made by a clinician after inspecting the wound, the surrounding tissue, vital signs, odor, color, drainage, time to heal, and so on. If indicated, then antibiotics r ok.