Acute Bacterial Meningitis

What is acute bacterial meningitis?

A life‑threatening infection of the meninges causing inflammation of the brain and spinal cord coverings, requiring immediate antibiotics.

What causes bacterial meningitis?

Bacterial invasion of the meninges leading to inflammation, increased intracranial pressure, neutrophilic CSF response, and decreased CSF glucose due to bacterial consumption.

What epidemiologic factors increase meningitis risk?

• Adolescents/young adults

• Close‑contact environments (dorms, camps)

• Respiratory droplet spread

What are major risk factors for bacterial meningitis?

• Close‑contact exposure

• Immunocompromised state

• Asplenia

• Skull fracture

• Cochlear implant

• Recent neurosurgery

What symptoms commonly occur in acute bacterial meningitis?

• Fever

• Neck stiffness

• Altered mental status

• Severe headache

• Photophobia

• Nausea/vomiting

• Positive Brudzinski/Kernig signs

What is Brudzinski’s sign?

Involuntary hip/knee flexion when the neck is passively flexed.

What is Kernig’s sign?

Pain/resistance when extending the knee with the hip flexed.

What physical exam findings are typical in bacterial meningitis?

• Neck stiffness

• Positive Brudzinski/Kernig

• Tachycardia

• Labored respirations

What rash is associated with meningococcal meningitis?

Petechial or purpuric rash due to meningococcemia.

What laboratory tests are used in evaluating suspected meningitis?

• CBC

• CMP

• CRP

• Procalcitonin

• Lactate

• Blood cultures

• Drug screen

What is the best diagnostic test for meningitis?

Lumbar puncture with CSF analysis and culture.

What CSF findings are characteristic of bacterial meningitis?

• High neutrophils

• Low glucose

• High protein

• High opening pressure

What are indications for CT scan BEFORE lumbar puncture?

• Focal neurologic deficits

• Papilledema

• Immunocompromised

• New‑onset seizure

• Recent neurosurgery

• Suspected mass lesion

Why should antibiotics not be delayed for imaging?

Delaying antibiotics increases mortality

What organisms commonly cause meningitis in infants <1 month?

Group B Streptococcus.

What organisms commonly cause meningitis in older infants and children?

Streptococcus pneumoniae and Neisseria meningitidis.

What organism most commonly causes meningitis in adolescents?

Neisseria meningitidis.

What organisms commonly cause meningitis in adults?

Streptococcus pneumoniae.

What organism commonly causes meningitis in immunocompromised patients?

Listeria monocytogenes.

What is the empiric antibiotic treatment for bacterial meningitis in patients >1 month old?

Vancomycin + ceftriaxone or cefotaxime

What is the empiric antibiotic treatment for neonates <1 month old?

Ampicillin + gentamicin

What supportive treatments are used in meningitis?

• IV fluids

• Acetaminophen

• Monitor mental status

• Seizure prophylaxis

What adjunctive therapy is recommended for pneumococcal meningitis?

Dexamethasone.

What complications can occur from bacterial meningitis?

• Seizures

• Hearing loss

• Hydrocephalus

• Septic shock

• DIC

What follow‑up is recommended after meningitis treatment?

Monitor neurologic status, repeat LP if no improvement, audiology testing in children.

What chemoprophylaxis is recommended for close contacts of meningococcal meningitis?

Rifampin, ciprofloxacin, or ceftriaxone.

Who should receive meningococcal conjugate vaccination (MenACWY)?

Routine at 11–12 years with booster at 16

Who should receive serogroup B meningococcal vaccination?

People ≥10 years at increased risk for meningococcal disease.

What is encephalitis?

Infection of brain parenchyma causing fever, headache, and prominent altered mental status.

What is the best treatment for suspected HSV encephalitis?

IV acyclovir

What is a CNS abscess?

Localized infection causing fever and focal neurologic deficits with ring‑enhancing lesions on imaging.

What is the best treatment for CNS abscess?

IV antibiotics + surgical drainage

What features suggest Lyme neuroborreliosis?

Facial nerve palsy, meningitis‑like symptoms, tick exposure.

What is the treatment for Lyme meningitis?

IV ceftriaxone

What features suggest subarachnoid hemorrhage rather than meningitis?

Sudden “worst headache of life,” thunderclap onset, CT showing blood, LP with xanthochromia.

What is the treatment for subarachnoid hemorrhage?

Neurosurgical emergency management

How does toxin ingestion mimic meningitis?

Altered mental status, abnormal vitals, positive drug screen.

How does migraine differ from meningitis?

No fever, no neck stiffness, normal CSF.

What are the highest‑yield clinical pearls for bacterial meningitis?

• Do NOT delay antibiotics

• LP is the best diagnostic test

• Neisseria is most common in adolescents

• Low CSF glucose + high neutrophils = bacterial meningitis

• Chemoprophylaxis required for close contacts