Neonatal meningitis

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Etiology & Pathogenesis - The Tiny Invaders

  • Causative Agents:

    • Early Onset (< 7 days): 📌 GEL
      • Group B Strep (GBS) - Most common
      • E. coli (esp. K1 strain)
      • Listeria monocytogenes
    • Late Onset (≥ 7 days):
      • GBS, E. coli
      • Staphylococci, Pseudomonas (nosocomial)
  • Pathogenesis:

    • Source: Maternal GU tract (early) or environment (late).
    • Route: Hematogenous spread → bacteremia → meningeal seeding.

E. coli with the K1 capsular antigen is highly neuroinvasive, making it a leading cause of gram-negative neonatal meningitis.

GBS pathogenesis in mice: vertical transmission & meningitis

Clinical Features - Subtle Signs, Big Trouble

Signs are notoriously non-specific and subtle in neonates. Look for a constellation of findings rather than a single sign.

  • Systemic: Temperature instability (fever or hypothermia), lethargy, poor feeding, irritability, vomiting, respiratory distress.
  • Neurologic: Seizures (often subtle: e.g., staring, lip-smacking), altered sensorium, high-pitched cry, apnea.
  • Fontanelle: Bulging or full anterior fontanelle is a late and unreliable sign.
  • Classic Signs: Nuchal rigidity and Kernig's/Brudzinski's signs are typically absent.

⭐ Paradoxical irritability (crying when cuddled, quiet when left alone) is a subtle but important clue.

Diagnosis - The Spinal Tap Story

  • Lumbar Puncture (LP) is mandatory on suspicion of meningitis.
    • Contraindications: Cardiorespiratory instability, signs of ↑ Intracranial Pressure (ICP) like bulging fontanelle or focal deficits, infection at the puncture site, significant coagulopathy.
  • CSF Analysis - Key Findings (Bacterial):
    • Appearance: Turbid/Purulent
    • Cells: ↑↑ Neutrophils (>80%); Total count often >1000/mm³
    • Protein: ↑ >100-150 mg/dL
    • Glucose: ↓ <40 mg/dL or CSF/Blood glucose ratio <0.4
    • Gram Stain & Culture: Gold standard for pathogen identification.
  • Adjunctive Tests:
    • Blood Culture: Often positive.
    • Latex Agglutination Test (LAT): For GBS, S. pneumoniae antigens.

⭐ In a traumatic (bloody) tap, a corrected WBC count is crucial. A common rule is to subtract 1 WBC for every 500-1000 RBCs in the CSF to estimate the true level of pleocytosis.

Management - Bug-Busting Bootcamp

  • Empiric Antibiotics: Initiate ASAP after lumbar puncture.
  • Duration of Therapy (Minimum):

    • Group B Strep: 14 days
    • Listeria monocytogenes: 14-21 days
    • Gram-Negative Bacilli (e.g., E. coli): 21 days
  • Supportive Care:

    • Maintain fluid & electrolyte balance
    • Control seizures (Phenobarbital)
    • Monitor for complications (SIADH, hydrocephalus)

Exam Pearl: Cefotaxime is preferred over Ceftriaxone in neonates. Ceftriaxone displaces bilirubin from albumin, increasing the risk of kernicterus, and can cause biliary sludging.

Neonatal Infection: Antibiotic Treatment Algorithm

Complications & Prognosis - The Aftermath

  • Acute: SIADH, subdural effusion/empyema, ventriculitis, brain abscess, communicating hydrocephalus.
  • Long-term Sequelae (25-50%):
    • Sensorineural hearing loss (most common)
    • Intellectual disability, epilepsy
    • Cerebral palsy, visual impairment
  • Prognosis:
    • Mortality: 10-15% (GBS/E. coli), higher with other gram-negatives.
    • Worse with seizures, coma, high CSF protein.

CT brain showing hydrocephalus post neonatal meningitis

⭐ Sensorineural hearing loss is the most common sequela. All survivors require an auditory assessment (BERA/OAE) before discharge.

High‑Yield Points - ⚡ Biggest Takeaways

  • Group B Streptococcus (GBS) is the leading cause of early-onset meningitis, while Coagulase-Negative Staphylococci (CoNS) is common in late-onset cases.
  • Clinical signs are often non-specific (lethargy, poor feeding). A bulging fontanelle is a more specific and crucial sign.
  • Lumbar puncture is the cornerstone of diagnosis; definitive diagnosis is by CSF culture.
  • Empirical treatment is typically Ampicillin + Gentamicin or Ampicillin + Cefotaxime.
  • Carries a high risk of severe long-term neurological sequelae.

Practice Questions: Neonatal meningitis

Test your understanding with these related questions

A 7-year-old boy is brought to the emergency department because of high-grade fever and lethargy for 4 days. He has had a severe headache for 3 days and 2 episodes of non-bilious vomiting. He has sickle cell disease. His only medication is hydroxyurea. His mother has refused vaccinations and antibiotics in the past because of their possible side effects. He appears ill. His temperature is 40.1°C (104.2°F), pulse is 131/min, and blood pressure is 92/50 mm Hg. Examination shows nuchal rigidity. Kernig and Brudzinski signs are present. A lumbar puncture is performed. Analysis of the cerebrospinal fluid (CSF) shows a decreased glucose concentration, increased protein concentration, and numerous segmented neutrophils. A Gram stain of the CSF shows gram-negative coccobacilli. This patient is at greatest risk for which of the following complications?

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Flashcards: Neonatal meningitis

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What is the first type of immunoglobulin produced in a neonate? _____

TAP TO REVEAL ANSWER

What is the first type of immunoglobulin produced in a neonate? _____

IgM

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