Bacterial Meningitis Lecture Notes

Jul 7, 2024

Bacterial Meningitis Lecture Notes

Definition and Importance

  • Definition: Infection of the meninges, specifically the subarachnoid space and brain
  • Seriousness: Potentially life-threatening; cautious approach needed, especially when differentiating from viral meningitis

Causes

  • Common Bacterial Agents:
    • Streptococcus pneumoniae
    • Neisseria meningitidis
    • Streptococcus agalactiae (Group B Strep)
    • Listeria monocytogenes
    • Haemophilus influenzae (less common now due to vaccination)

Epidemiology

  • Newborns: Mainly Group B Strep (70%), Listeria, and pneumococcus
  • 1 month to 2 years: Leading cause is Streptococcus pneumoniae
  • 2 years to young adults: Predominantly Neisseria meningitidis
  • Adults: Pneumococcus dominates with 60% and Neisseria meningitidis at 20%
  • Elderly (60+ years): Mainly pneumococcus and Listeria

Clinical Features

  • Newborns: Listlessness, temperature instability, high-pitched cry, weak suck, jaundice, vomiting, diarrhea, respiratory distress
  • Children (1-4 years): Fever (>90%), vomiting, stiff neck appears
  • Older Children & Adults: Fever, headache, stiff neck (meningismus), confusion
  • Neonates: Less classic signs (e.g., no stiff neck)

Diagnostic Signs

  • Kernig's Sign: Pain upon knee extension
  • Brudzinski's Sign: Hip flexion upon neck flexion
  • Other Indicators: Cranial nerve palsies (brain stem involvement), petechial rash (especially with Neisseria), seizures, hemiparesis

Focus on Neisseria Meningitidis

  • Population: Young adults, college students, military personnel
  • Symptoms: Abrupt onset, fever, stiff neck, low BP, rash
  • Fatality: 9-12% with 40% experiencing meningococcemia
  • Symptoms Progression: Petechial or purpuric rash that does not blanch

Rapid/Alternative Diagnostics

  • Rocky Mountain Spotted Fever: Can mimic meningococcemia, especially in southeastern US
  • Differential: Use both doxycycline (RMSF) and appropriate antibacterial treatment if uncertain

Treatment Protocols

  • Newborns: Cefotaxime preferred over ceftriaxone
  • Empirical Treatment (1 month-50 years): Ampicillin, ceftriaxone, vancomycin, dexamethasone
  • Head Trauma/Neurosurgery Patients: Vancomycin and cefepime, or meropenem + vancomycin
  • Specific Pathogens Treatments:
    • Streptococcus pneumoniae: Vancomycin, ceftriaxone, dexamethasone
    • Haemophilus influenzae & Pseudomonas: Anti-Pseudomonas cephalosporin + gentamicin
    • Listeria: Ampicillin + gentamicin (21 days)
    • Staphylococcus: Vancomycin
    • Meningococcal: Ceftriaxone + dexamethasone

Laboratory Findings in Meningitis

  • Elevated Opening Pressure during lumbar puncture
  • High White Cell Count (more than 5 is abnormal)
    • Predominance of Neutrophils
    • Exceptions: Newborn infections, Listeria, tuberculosis meningitis
  • Low Glucose Levels in CSF
  • High Protein Levels
  • Gram Stain helpful for choosing antibiotics rapidly
  • Blood Cultures Useful if LP is contraindicated

Advanced Diagnostic Tools

  • PCR & Immunochromatographic Tests: Effective in early bacterial identification, especially with prior antibiotic use

Management

  • Initial Empirical Treatment: Broad-spectrum antibiotics + dexamethasone
  • Adjust Based on Gram Stain/Cultures: Tailor antibiotics accordingly
  • Private Physician Scenario: Immediate administration of antibiotics if hospital transfer is delayed
  • IDSA Guidelines: Blood cultures, lumbar puncture, empirical antibiotics, and dexamethasone based on patient presentation