Makindo Medical Notes

Bordetella pertussis enters the respiratory tract after inhalation and destroys the ciliated epithelial cells of the trachea and bronchi through various toxins. If there is a 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 DTP (Diphtheria, Tetanus, and Pertussis) vaccine.
• The Vaccine is not always effective.
• 30% of severe infections are via a fully vaccinated sibling.
• Vaccinating the mother during pregnancy reduces risk in babies.
• Immunity wanes steadily throughout childhood.

Aetiology

• Caused by infection with Bordetella pertussis .
• Similar respiratory infections can be caused by Bordetella parapertussis.
• Co-infection with RSV is common
• The incubation period is short, typically 1-2 weeks.
• The bacterium destroys the ciliated epithelial cells in the respiratory tract, impairing the body's ability to clear mucus.

Toxin Production

• Pertussis toxin: Activates host cell production of cAMP, altering protein synthesis regulation and contributing to prolonged symptoms.
• Tracheal cytotoxin: Causes destruction of the ciliated epithelial cells of the trachea and bronchi.
• Hemagglutinin: A cell surface protein that aids bacterial adhesion to host cells.
• Adenylate cyclase toxin: Disrupts host immune responses, weakening bacterial clearance.

Characteristics

• Small, Gram-negative coccobacillus.
• Obligate aerobes with fastidious growth requirements.
• Non-motile and non-capsulated.

Clinical Features

Apnoea and bouts of coughing ending with vomiting (± cyanosis) worse at night or after feeds

• Initially presents as a mild coryza-type illness (runny nose, mild cough).
• Progresses to severe bouts of paroxysmal coughing with the characteristic "whoop" sound.
• In infants under 6 months, it can cause apnoea episodes (pauses in breathing)
• Risk of neurological damage due to hypoxia.
• Complications can include bronchiectasis , cyanosis (bluish skin), and lobar collapse.

Investigations

• Pernasal swab for culture, usually on Bordet-Gengou agar .
• Other methods include PCR testing for more rapid results in suspected cases.

Management

• Refer infants under 6 months (apnoea risk) and those at risk for specialised care.
• Inform the infectious diseases consultant, as pertussis is a notifiable disease .
• Treat with Azithromycin 500 mg once daily for 3 days or similar macrolides.
• Prophylactic treatment of unimmunised contacts, such as siblings, is recommended to prevent spread.
• Severe cases may need ventilating and even ECMO

Complications

• Prolonged illness (the ‘100 day cough’).
• Coughing bouts may cause petechiae (eg on cheek), conjunctival, retinal & CNS bleeds (rare)
• Cough and apnoea, inguinal hernias ± lingual frenulum tears.
• Deaths may occur (esp. in infants), as may late bronchiectasis.