Acute community-acquired bacterial meningitis

Community-acquired bacterial meningitis is a significant cause of morbidity and mortality. The most common causative organisms are Streptococcus pneumoniae and Neisseria meningitidis. The incidence of Listeria monocytogenes infection increases over age 50 years and in those with compromised cell-mediated immunity. Symptoms and signs are not sensitive or specific enough to diagnose community-acquired bacterial meningitis. A lumbar puncture for cerebrospinal fluid is needed to reach the diagnosis, to identify the organism, and to determine antimicrobial susceptibilities. Computed tomography of the head is not necessary in all patients prior to a lumbar puncture, only in immunocompromised patients and in those who have features suggestive of or who are at risk of increased intracranial pressure. Appropriate empiric antimicrobials should be started as soon as possible.