mrcem2-1056

A middle-aged intravenous drug user with an unstable living situation complains of intense back pain, fever, and weakness in the left leg. The pain has been disrupting his sleep and making it hard for him to walk. During the examination, tenderness is observed in the lower lumbar spine, and there is weakness in left knee extension and foot dorsiflexion.
What is the probable organism responsible for these symptoms in this individual?