A 72-year-old woman without a history of spinal injury was admitted to our hospital with prolonged severe back pain and high fever. Clinical laboratory findings and magnetic resonance imaging (MRI) revealed severe inflammation of the L2 and L3 lumbar vertebrae. Meropenem trihydrate administration improved her symptoms. Klebsiella pneumoniae isolated from the patient's blood indicated that the organism caused the spontaneous pyogenic spondylitis.