Bordetella pertussis

Snapshot

• A 2-month-old girl infant presents to the emergency room with a 3-day history of a cough and post-tussive emesis. Her mother reports that while she had the Tdap vaccine during pregnancy, the father did not. For the past 2 weeks, the father has had a persistent dry cough. The infant’s temperature is 100.4°F (38°C), pulse is 160/min, and respirations are 60/min. Physical exam reveals an infant with a dry cough on expiration and a whooping sound on inspiration. Fine crackles are heard bilaterally on auscultation. She is admitted and given antibiotics.

Introduction

• Classification 
  • Bordetella pertussis
    • a gram-negative aerobic coccobacilli
  • transmission
    • respiratory droplets
• Epidemiology
  • demographics
    • infants are especially at risk
      • < 6 months of age
      • too young to be vaccinated
    • unvaccinated children
  • risk factors
    • exposure to infected people
    • incomplete vaccination
    • HIV exposure
• Pathogenesis
  • bacteria colonizes mucosal surface
  • pertussis toxin binds to and activates adenylate cyclase by inhibiting Gi 
    • impairs phagocytosis, allowing the bacteria to survive
  • tracheal cytotoxin 
    • peptidoglycan fragment that impairs cilia, preventing normal clearance of respiratory secretions
  • low lung volume at the beginning of inspiration causes strong inspiration and inspiratory “whoop”
• Associated conditions
  • whooping cough
  • 100-day cough
• Prevention
  • DTaP vaccine
    • vaccine against diphtheria, tetanus, and pertussis
    • acellular pertussis vaccine
    • 5 doses before school-age, completed by 4-6 years of age
  • Tdap vaccine
    • booster vaccine at 11-12 years of age
    • should also be given to pregnant mothers and those around them
• Prognosis
• can be fatal in infants

Presentation

• Symptoms
  • catarrhal stage (first)
    • low-grade fevers
    • coryza
  • paroxysmal stage (second)
    • dry cough and whoop
    • post-tussive vomiting
  • convalescent stage (third)
    • recovery
• Physical exam
  • whooping cough in children
    • dry cough on expiration
    • “whoop” on inspiration
  • 100-day cough in adults
    • post-tussive vomiting
• paroxysmal cough

Studies

• Labs
  • culture in
    • Bordet-Gengou agar
    • Regan Lowe medium
  • polymerase chain reaction
  • serology
  • requires nasopharyngeal secretions on a special swab, as the bacteria will not grow on cotton
• Making the diagnosis
• based on clinical presentation and laboratory studies

Differential

• Mycoplasma pneumonia
  • distinguishing factor
• also presents with a dry cough, but no whooping cough and no posttussive vomiting

Complications

• Pneumonia
• Failure to thrive
• Death
  • especially in young infants
• Apnea
  • especially in young infants