The spinal cord (usually an infection of the tissue covering the spinal cord, called an epidural abscess).
One or more vertebrae (osteomyelitis).
The facet joints, which may be the site of infectious arthritis.
Bacteria that infect the spine usually originate in other parts of the body and are carried to the spine through the bloodstream. But bacteria can enter the spine directly during surgery or injection treatments, as the result of injury, or as a result of IV drug use.