Bacterial Meningitis I: Introduction

Bacterial meningitis is an acute bacterial infection involving the leptomeninges and the cerebrospinal fluid within the subarachnoid space.

Many causative bacteria asymptomatically colonize the nasopharynx and spread via respiratory droplets, while the Group B streptococcus often transmits from mother to infant during childbirth.

In adults, the main pathogens are Streptococcus pneumoniae and Neisseria meningitidis, while Listeria monocytogenes is more common in older adults and immunocompromised individuals.

Clinical features include fever, severe headache, and neck stiffness. As inflammation progresses, altered mental status and focal neurological deficits, such as hemiparesis, may develop.

Physical examination may reveal signs of meningeal inflammation. The Kernig sign is elicited when the hip is flexed in a supine patient, causing pain in the lower back or posterior thigh.

The Brudzinski sign is present when passive neck flexion leads to involuntary hip and knee flexion, which lowers traction on the irritated meninges.