Bacterial Meningitis

Bacterial meningitis is a life-threatening medical emergency with mortality rates of 6–54% depending on pathogen and setting, and up to 25% of survivors develop neurological sequelae. [1-2] The most common causative organisms in adults are Streptococcus pneumoniae (~72%) and Neisseria meningitidis (~11%); in neonates, E. coli and Group B Streptococcus predominate. [1][3]

• Cardinal symptoms: Headache (84%), fever (74%), neck stiffness (74%), altered mental status (median GCS 11), nausea (62%) [1]
• Onset is typically acute — ~50% present within 24 hours of symptom onset [1]
• Ask about symptom progression: rapid deterioration over hours suggests bacterial etiology over viral
• Associated symptoms: Photophobia, vomiting, seizures, rash (especially petechial/purpuric in meningococcal disease)
• Important negatives: No recent head trauma, no neurosurgical procedures, no VP shunt (which would suggest healthcare-associated meningitis)
• Exposure history: Sick contacts, dormitory/barracks living, recent travel, daycare exposure
• Vaccination status: Pneumococcal, meningococcal, Hib vaccines [3]
• Recent infections: Otitis, sinusitis, pneumonia — extrameningeal foci present in ~43% of cases [2]

• Petechial or purpuric rash — present in ~50% of meningococcal meningitis; high specificity (83–92%) for meningococcal disease [1-2]
• Rapidly declining GCS or coma (13% present comatose) [1]
• New-onset seizures (focal or generalized)
• Focal neurological deficits: Aphasia, hemiparesis (22%), cranial nerve palsies (9%) [1]
• Signs of septic shock: Hypotension, tachycardia, DIC
• Bulging fontanelle in infants
• Papilledema — suggests elevated ICP; obtain imaging before LP
• Delay in antibiotics >6 hours increases mortality from 6% to 45% [1]

Empiric Treatment (start within 1 hour of presentation): [1][3]

Add vancomycin if local ceftriaxone-resistant pneumococcus prevalence >1% [1]

Key adult dosing (normal renal/hepatic function): Ceftriaxone 4 g/day, vancomycin 30–60 mg/kg/day (target trough 15–20 mg/mL), ampicillin 12 g/day [2]

Adjunctive dexamethasone: 10 mg IV q6h × 4 days in adults; give with or before the first dose of antibiotics. [1] Reduces mortality in pneumococcal meningitis from 52% to 26%. [1] Discontinue immediately if Listeria is identified — associated with increased mortality (OR 4.58). [1] Not recommended in neonates. [2]

Contraindicated/cautions

• Oral step-down antibiotics are not recommended [3]
• Avoid moderate hypothermia and glycerol — associated with worse outcomes [2]

• NPO initially if altered mental status or risk of aspiration
• Ensure adequate IV hydration; avoid overhydration which may worsen cerebral edema
• No specific dietary triggers or long-term dietary management

• Neurologic: Headache severity/quality, photophobia, phonophobia, vision changes, weakness, numbness, seizure activity
• Constitutional: Fever, chills, rigors, malaise, myalgias
• ENT: Ear pain, sinus pressure/drainage, hearing changes (baseline and new)
• Respiratory: Cough, dyspnea (concurrent pneumonia in ~9%) [1]
• Skin: Rash — specifically petechial, purpuric, or non-blanching
• GI: Nausea, vomiting, diarrhea
• Musculoskeletal: Leg pain (especially in children with meningococcal disease) [4]

• Collateral: Witnesses to onset, timeline of symptom progression, baseline mental status, recent antibiotic use (partially treated meningitis alters CSF findings)
• Exposures: Household contacts with meningococcal disease, dormitory/military barracks, daycare attendance
• Family history: Complement deficiency (increases susceptibility to meningococcal disease), asplenia, immunodeficiency syndromes
• Social context: Living situation (crowded housing), occupation (laboratory workers handling N. meningitidis), recent travel to meningitis belt (sub-Saharan Africa)

• Age extremes: Neonates and adults >50 years [1]
• Immunocompromise: Present in ~33% of adults with bacterial meningitis — HIV/AIDS, organ transplant, asplenia, complement deficiency, chronic corticosteroid use [2]
• Anatomic: CSF leak, cochlear implants, basilar skull fracture, recent neurosurgery
• Contiguous infection: Otitis media, sinusitis, mastoiditis (especially pneumococcal) [2]
• Unvaccinated status against pneumococcus, meningococcus, or Hib [3]
• Crowded living: Dormitories, military barracks, prisons

• Viral meningitis (most common cause of meningitis overall; ~72% of cases) — typically milder, CSF lymphocytic predominance, normal glucose [1]
• Subarachnoid hemorrhage — thunderclap headache, acute onset; CT head ± LP
• Herpes simplex encephalitis — altered mental status, seizures, temporal lobe involvement; requires acyclovir
• Tuberculous meningitis — subacute onset (>5 days), lymphocytic CSF, very low glucose; consider in immunocompromised [5]
• Fungal meningitis (Cryptococcus) — indolent course, especially in HIV with CD4 <100
• Brain abscess/subdural empyema — focal deficits, imaging abnormalities
• Drug-induced aseptic meningitis — NSAIDs, trimethoprim, IVIG [6]
• Carcinomatous/lymphomatous meningitis — history of malignancy, cytology positive
• Autoimmune meningitis — SLE, sarcoidosis, Behçet disease [5]

• Prior episodes of meningitis (recurrent meningitis suggests anatomic defect or complement deficiency)
• History of splenectomy or functional asplenia
• HIV status and CD4 count
• History of head trauma or neurosurgery
• Cochlear implants (increased pneumococcal meningitis risk)
• Chronic conditions: Diabetes, alcoholism, cirrhosis, chronic kidney disease
• Vaccination history

• Vitals: Fever (74%), tachycardia, hypotension (suggests septic shock — poor prognostic sign)
• Mental status: GCS assessment — median GCS is 11 at presentation; 13% present comatose [1]
• Neck stiffness/nuchal rigidity: Present in 74–86% [1][3]
• Kernig and Brudzinski signs: High specificity (up to 95%) but very poor sensitivity (5–30%) — cannot be used to rule out meningitis [2-3]
• Jolt accentuation test: Sensitivity 52–65% [3]
• Skin: Petechial/purpuric rash — especially in meningococcal disease (63–80%) [2]
• Cranial nerves: Palsies in ~9% [1]
• Fundoscopy: Papilledema (suggests elevated ICP — image before LP)
• Fontanelle in infants: Bulging suggests elevated ICP
• Ears/sinuses: Evaluate for otitis, mastoiditis, sinusitis as source

Blood

• CBC with differential (leukocytosis; serum WBC >10 × 10⁹/L is a risk factor for bacterial etiology) [1]
• Blood cultures (positive in up to 75%) — obtain before antibiotics [2]
• CRP, procalcitonin (may help differentiate bacterial from viral) [6]
• BMP (glucose for CSF:serum ratio), coagulation studies
• Lactate (if concern for sepsis)

CSF (gold standard): [2][7-8]

• CSF lactate >35.1 mg/dL (3.9 mmol/L): 93–95% sensitive, 94–99% specific for bacterial meningitis if obtained before antibiotics [7]
• Multiplex PCR panel: >95% sensitivity and specificity; especially valuable if antibiotics given before LP [7]

• CT head before LP is indicated only if: New-onset seizures, focal neurological deficits, papilledema, immunocompromised state, or moderate-to-severe impairment of consciousness [2]
• Do NOT delay antibiotics for imaging — start empiric treatment and dexamethasone before CT [1-2]
• Absence of the above features has a 97% negative predictive value for intracranial abnormality [2]
• Overuse of pre-LP imaging is common (67% of patients without indication still undergo CT) and delays treatment [1]
• MRI: Superior for detecting complications (empyema, abscess, infarction, ventriculitis) — obtain if clinical deterioration or failure to improve within 48 hours [2]

The following figure illustrates the major intracranial complications of bacterial meningitis, including hydrocephalus, cerebral infarction, transtentorial herniation, and seizure activity:

• Bacterial Meningitis Score (pediatric, age 2 months–18 years): Positive Gram stain (2 pts), CSF protein >80 mg/dL (1 pt), blood ANC >10,000 (1 pt), seizures (1 pt), CSF neutrophils >1,000 (1 pt). Score ≥2 suggests bacterial meningitis (sensitivity 99.3%, NPV 99.7%) [1]
• Adult risk score (Gram stain–negative): Immunosuppression, age >60, abnormal neuro exam, CSF glucose <45 mg/dL, CSF protein >100 mg/dL, serum WBC >12,000. Zero risk factors = essentially zero risk of bacterial meningitis [1]
• Latex agglutination for bacterial antigens — variable sensitivity, may be useful in partially treated cases [7]
• 16S rRNA PCR — useful when cultures are negative due to prior antibiotics [6]

• Not a primary diagnostic tool for meningitis
• Obtain if hemodynamic instability or septic shock to evaluate for myocarditis, arrhythmias, or QTc prolongation (relevant if using fluoroquinolones for prophylaxis)
• Meningococcal sepsis can cause myocardial dysfunction

• Bacterial meningitis is a neurological emergency requiring immediate empiric treatment
• The classic triad (fever, neck stiffness, altered mental status) is present in only 40–50% of patients, but 95% have at least 2 of 4 cardinal symptoms (headache, fever, neck stiffness, altered mental status) [6][11]
• Atypical presentations are common in neonates (nonspecific: poor feeding, irritability), elderly (may lack meningeal signs), and immunocompromised patients [1-2]
• Severity stratification: Low GCS, seizures, focal deficits, septic shock, CSF WBC <1,000, and positive blood cultures predict worse outcomes [1][6]
• Complications: Hearing loss, hydrocephalus, cerebral infarction (up to 30% in pneumococcal), cerebral venous thrombosis, subdural empyema, brain abscess, DIC [2][12]

Immediate stabilization

• ABCs — intubate if GCS ≤8 or airway compromise
• IV access, fluid resuscitation if septic shock
• Dexamethasone 10 mg IV (adults) — give with or just before first antibiotic dose [1]
• Empiric antibiotics within 1 hour — do not delay for imaging or LP [1][3]

Empiric antibiotics (adults 18–49 years): Ceftriaxone 2 g IV q12h + vancomycin 15–20 mg/kg IV q8–12h [2-3]

• Add ampicillin 2 g IV q4h if age ≥50, pregnant, or immunocompromised (Listeria coverage) [1]
• Continue dexamethasone 10 mg IV q6h × 4 days; discontinue if Listeria confirmed [1-2]

Pathogen-directed therapy once culture and sensitivities available: [3]

• Penicillin-susceptible pneumococcus: Penicillin G or ampicillin (10–14 days)
• Meningococcus: Penicillin G or ceftriaxone (7 days)
• Listeria: Ampicillin ± gentamicin (≥21 days)
• MRSA: Vancomycin (≥14 days)

ICP management: Elevate head of bed 30°, avoid hyperthermia, consider osmotic therapy if signs of herniation; neurosurgical consultation for hydrocephalus or empyema [2]

• All confirmed or suspected bacterial meningitis requires hospital admission — typically to the ICU given high mortality and risk of rapid deterioration [11]
• ICU criteria: GCS ≤12, hemodynamic instability, seizures, respiratory compromise, DIC
• Step-down when: Clinically improving, hemodynamically stable, no seizures, organism identified and susceptibilities known
• Neurosurgery consultation: Hydrocephalus, subdural empyema, brain abscess, need for ICP monitoring [2]
• Infectious disease consultation: Recommended for all cases to guide antibiotic optimization and duration
• Public health notification: Meningococcal disease is reportable — notify local health department immediately for contact tracing and chemoprophylaxis [13]

Chemoprophylaxis for close contacts: [3][14]

• Meningococcal: Ciprofloxacin 500 mg PO × 1 dose (adults), rifampin 600 mg PO q12h × 2 days, or ceftriaxone 250 mg IM × 1 dose. Initiate within 24 hours of index case identification
• H. influenzae type B: Rifampin 20 mg/kg/day (max 600 mg) × 4 days for household contacts with unvaccinated children <4 years [3]
• Close contacts = household members, roommates, daycare contacts, anyone exposed to oral secretions [15]

Post-discharge follow-up

• Audiology evaluation — hearing loss is the most common sequela; prompt assessment with consideration for cochlear implants [6][16]
• Neurocognitive assessment — cognitive impairment, memory deficits, and sleep disorders are common long-term sequelae [2][17]
• Pneumococcal vaccination if not previously vaccinated — to prevent recurrence [16]
• Evaluate for anatomic predisposition (CSF leak, skull base defect) in recurrent cases

Return precautions: Instruct patients/families to return immediately for recurrent fever, worsening headache, new neurological symptoms (weakness, vision changes, seizures), altered mental status, or new rash.

Expected recovery: Clinical improvement typically begins within 48–72 hours of appropriate therapy. Failure to improve should prompt repeat imaging and consideration of complications. [2]

1. Progress and Challenges in Bacterial Meningitis: A Review. — Hasbun R. The Journal of the American Medical Association. 2022.

2. Community-Acquired Bacterial Meningitis. — van de Beek D, Brouwer MC, Koedel U, Wall EC. Lancet. 2021.

3. Aseptic and Bacterial Meningitis: Diagnosis, Treatment, and Prevention. — Krebs L, Durden B, Saguil A. American Family Physician. 2026.

4. Pre-Hospital Symptoms Associated With Acute Bacterial Meningitis Differs Between Children and Adults. — Hovmand N, Christensen HC, Lundbo LF, et al. Scientific Reports. 2023.

5. Dilemmas in the Diagnosis of Acute Community-Acquired Bacterial Meningitis. — Brouwer MC, Thwaites GE, Tunkel AR, van de Beek D. Lancet. 2012.

6. Acute Bacterial Meningitis in Adults. — McGill F, Heyderman RS, Panagiotou S, Tunkel AR, Solomon T. Lancet. 2016.

7. Cerebrospinal Fluid Analysis. — Shahan B, Choi EY, Nieves G. American Family Physician. 2021.

8. Practice Guidelines for the Management of Bacterial Meningitis. — Tunkel AR, Hartman BJ, Kaplan SL, et al. Clinical Infectious Diseases : An Official Publication of the Infectious Diseases Society of America. 2004.

9. Emergency Diagnosis and Treatment of Adult Meningitis. — Fitch MT, van de Beek D. The Lancet. Infectious Diseases. 2007.

10. Community-Acquired Bacterial Meningitis in Adults. — van de Beek D, de Gans J, Tunkel AR, Wijdicks EF. The New England Journal of Medicine. 2006.

11. High Risk and Low Prevalence Diseases: Adult Bacterial Meningitis. — Pajor MJ, Long B, Koyfman A, Liang SY. The American Journal of Emergency Medicine. 2023.

12. Pneumococcal Meningitis in Adults: Spectrum of Complications and Prognostic Factors in a Series of 87 Cases. — Kastenbauer S, Pfister HW. Brain : A Journal of Neurology. 2003.

13. Meningococcal Vaccination: Recommendations of the Advisory Committee on Immunization Practices, United States, 2020. — Mbaeyi SA, Bozio CH, Duffy J, et al. MMWR. Recommendations and Reports : Morbidity and Mortality Weekly Report. Recommendations and Reports. 2020.

14. Meningococcal Disease. — Lucy A. McNamara and Amy B. Rubis CDC Yellow Book. 2025.

15. Prevention of Meningococcal Disease. — Gardner P. The New England Journal of Medicine. 2006.

16. Update on Community-Acquired Bacterial Meningitis: Guidance and Challenges. — van Ettekoven CN, van de Beek D, Brouwer MC. Clinical Microbiology and Infection : The Official Publication of the European Society of Clinical Microbiology and Infectious Diseases. 2017.

17. Neurological Sequelae of Bacterial Meningitis. — Lucas MJ, Brouwer MC, van de Beek D. The Journal of Infection. 2016.