Bordetella pertussis (Whooping cough)
😷 Bordetella pertussis enters the respiratory tract after inhalation and destroys the ciliated epithelial cells of the trachea and bronchi through toxins.
🧪 If strong clinical suspicion of whooping cough, refer to microbiology for a pernasal swab for immediate processing to improve isolation rates of B. pertussis.
📖 About
- 🔊 The characteristic "whoop" is the sudden inspiration heard at the end of a bout of coughing.
- 😮 Whoops (not always heard) are caused by inspiration against a closed glottis.
- 👤 Humans are the only known reservoir for Bordetella pertussis.
💉 Vaccination
- 🛡️ Whooping cough is reduced with the DTP (Diphtheria, Tetanus, Pertussis) vaccine.
- ⚠️ The vaccine is not always fully protective → ~30% of severe infections occur in fully vaccinated siblings.
- 🤰 Maternal vaccination during pregnancy reduces risk in babies.
- 📉 Immunity wanes steadily through childhood → booster programmes are important.
🦠 Aetiology
- Caused by infection with Bordetella pertussis.
- Similar illness can be caused by Bordetella parapertussis.
- 🤧 Co-infection with RSV is common.
- Incubation period: ⏳ 1–2 weeks.
- Pathogenesis: Destroys ciliated respiratory epithelium → impaired mucus clearance.
☣️ Toxin Production
- 🧪 Pertussis toxin: ↑ host cell cAMP → disrupts protein regulation, prolongs symptoms.
- 💥 Tracheal cytotoxin: Destroys ciliated epithelial cells in trachea & bronchi.
- 🩸 Hemagglutinin: Adhesion molecule helping bacterial attachment.
- 🛑 Adenylate cyclase toxin: Suppresses host immunity, reducing bacterial clearance.
🔬 Characteristics
- Gram-negative coccobacillus.
- Strict aerobe, fastidious growth.
- Non-motile, non-capsulated.
🩺 Clinical Features
👶 Infants may present with apnoea and bouts of coughing ending in vomiting ± cyanosis. Symptoms are often worse at night or after feeds.
⚠️ Hypoxia → risk of neurological damage.
- Stage 1 (Catarrhal): 🤧 Coryza-type illness (runny nose, mild cough, malaise).
- Stage 2 (Paroxysmal): Violent bouts of coughing with/without characteristic "whoop".
- Stage 3 (Convalescent): Gradual recovery but cough may last weeks → “100 day cough.”
- Complications: 🌬️ Bronchiectasis, cyanosis, lobar collapse, CNS bleeds (rare).
🧪 Investigations
- 👃 Pernasal swab for culture on Bordet-Gengou agar.
- ⚡ PCR testing → rapid, sensitive diagnosis.
💊 Management
- 🏥 Refer infants <6 months (apnoea risk) and vulnerable patients for specialist care.
- 📢 Notify infectious diseases consultant → pertussis is a notifiable disease.
- Antibiotics: Azithromycin 500 mg daily × 3 days (or other macrolides).
- 👨👩👧 Prophylaxis: Treat unimmunised close contacts (siblings, household members).
- Critical care: Severe cases may require ventilation or ECMO support.
⚠️ Complications
- 🕰️ Prolonged cough (“100-day cough”).
- 🩸 Coughing bouts → petechiae, conjunctival haemorrhage, rare CNS bleeds.
- 💔 Cough-related injuries: hernias, lingual frenulum tears.
- ☠️ Infant mortality possible; late bronchiectasis in survivors.
