[Meningitis (II)--acute bacterial meningitis]

Acute meningitis is a medical emergency, particularly in patients with rapidly progressing disease, mental status changes or neurological deficits. The majority of cases of bacterial meningitis are caused by a limited number of species, i.e. Streptococcus pneumoniae, Neisseria meningitis, Listeria monocytogenes, group B Streptococci (Streptococcus agalactiae), Haemophilus influenzae and Enterobacteriaceae. Many other pathogens can occasionally cause bacterial meningitis, often under special clinical circumstances. Treatment of meningitis includes two main goals: Eradication of the infecting organism, and management of CNS and systemic complications. Empiric therapy should be initiated without delay, as the prognosis of the disease depends on the time when therapy is started. One or two blood cultures should be obtained before administering the first antibiotic. Empiric therapy is primarily based on the age of the patient, with modifications if there are positive findings on CSF gram stain or if the patient presents with special risk factors. It is safer to choose regimens with broad coverage, as they can usually be modified within 24-48 hours, when antibiotic sensitivities of the infecting organism become available. Adjunctive therapy with dexamethasone is also administered in severely ill patients concomitantly with the first antibiotic dose. In patients who are clinically stable and are unlikely to be adversely affected if antibiotics are not administered immediately, including those with suspected viral or chronic meningitis, a lumbar puncture represents the first step, unless there is clinical suspicion of an intracerebral mass lesion. Findings in the CSF and on CT scan, if performed, will guide the further diagnostic work-up and therapy in all patients.