(bacterial meningitis) Bacterial infections of the leptomeninges and subarachnoid space, frequently involving the cerebral cortex, cranial nerves, cerebral blood vessels, spinal cord and nerve roots; causative organism varies with age and clinical status (eg, postoperative, immunodeficient, posttraumatic states); clinical manifestations include the acute onset of fever, stiff neck, altered mentation, seizures, and focal neurologic deficits; death may occur within 24 hours of disease onset; pathologic features include a purulent exudate in the subarachnoid space, and diffuse inflammation of neural and vascular structures.

(bacterial meningitis) Inflammation of the membranes surrounding the brain and spinal cord due to a bacterial infection.

Bacterial meningitis is a rare but serious inflammation of the meninges caused by various bacteria. Streptococcus pneumoniae , Haemophilus influenzae type b (Hib), and Neisseria meningitidis are the predominant causative pathogens in both adults and children.