3.7
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.
Bacterial meningitis is a severe, life-threatening inflammation of the meninges, particularly the pia mater and arachnoid mater, affecting the subarachnoid space, ventricles, and cerebrospinal fluid (CSF). If untreated, it can lead to significant neurological complications or death.
Common pathogens vary with age and immune status. In adults, major organisms include Streptococcus pneumoniae, Neisseria meningitidis, and Haemophilus influenzae. Streptococcus agalactiae (group B streptococcus, more common in neonates but possible in adults with risk factors). Other important causes include Listeria monocytogenes (in elderly and immunocompromised individuals), Mycobacterium tuberculosis, and non-typhoidal Salmonella. Predisposing factors include otitis media, sinusitis, pneumonia, and immunosuppression.
Many causative bacteria, including meningococcus, pneumococcus, and H. influenzae, are often carried asymptomatically in the nasopharynx and spread via respiratory droplets or secretions. Group B streptococcus colonizes the gastrointestinal or genital tract and can be transmitted during childbirth.
Symptoms reflect systemic infection, meningeal irritation, and neurological involvement. Systemic features include fever, chills, and tachycardia. Meningeal signs include severe headache, photophobia, neck stiffness, and positive Kernig sign (pain on knee extension due to meningeal stretch) and Brudzinski sign (involuntary hip and knee flexion with neck flexion). Neurological features include altered consciousness, cranial nerve palsies, focal deficits, seizures, papilledema, and projectile vomiting in children with raised intracranial pressure.
Meningococcal meningitis may present with a petechial or purpuric rash. A severe complication, purpura fulminans, involves disseminated intravascular coagulation, skin necrosis, multi-organ failure, and possible death.
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.
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