Bordetella pertussis

Categorization
Cell Wall: Gram Negative Shape: Coccoid Rod
Metabolism: Obligate Aerobe
Transmission
  • Pertussis is one of the most communicable diseases and is spread by aerosolized droplets or infected respiratory secretions. Patients are most infectious in the "Catarrhal Stage" (See below).
Culture and Detection
  • Selective media for B. pertussis is Bordet-Gengou (Potato-blood) agar or a charcoal medium.
Virulence Factors
  • Overview
    • B. pertussis elaborates a variety of exotoxins and adhesion factors which are critical for its disease pathogenesis. However, the precise mechanism by which these toxins contribute the to the characteristic clinical consequences of pertussis is not well-understood. Overall, B. pertussis remains a localized infection of the upper respiratory tract with little invasion beyond the ciliated respiratory epithelium to which it adheres.
  • Exotoxins
    • Pertussis Toxin: Pertussis Toxin is an A-B Toxin that deranges host immunity
    • Filamentous Hemagglutinin: Allows attachment to ciliated cells of the respiratory epithelium
    • Tracheal Cytotoxin: Causes death of ciliated cells of the respiratory epithelium
Clinical Consequences
  • Overview
    • The characteristic clinical syndrome caused by B. pertussis is called "Whooping Cough" and occurs in three stages.
  • Catarrhal Stage:
    • This is the incubation period of the disease and lasts 1-2 wks. Symptomology is very similar to a traditional upper respiratory infection and includes mild coughing, low fever, and coryza. Individuals are most infectious during this stage.
  • Paroxysmal Stage:
    • This is the stage which gives "Whoooping Cough" its namesake and lasts 2-4wks. It is characterized by spasmodic episodes of several non-productive coughs. These episodes are followed by an inspiration against a closed epiglottis which gives a "Whooping" sound. Vomiting is frequent after episodes of coughing.
  • Convalescent Stage
    • This stage may last months and is characterized by a gradual reduction in the frequency and intensity of coughs.
Laboratory
  • Lymphocytosis
    • An increase in the number of total blood lymphocytes is a notable feature of B. pertussis infection and mimics a viral syndrome. Lymphocytosis is likely due to systemic spread of one or several pertussis exotoxins, possibly Pertussis Toxin itself.
Immunity
  • Humoral immunity to B. pertussis is protective and involves elaboration of antibodies against Filamentous Hemagglutinin and Pertussis Toxin.
Vaccination
  • Vaccine against B. pertussis is highly effective and is part of the DPT vaccine (P for Pertussis). Historically, heat-killed organisms were used but are now being replaced by acellular vaccines to purified Fillamentous Hemagglutinin and Pertussis Toxin.
Treatment
  • Erythromycin: Antibiotics are only effective if given in the "Catarrhal Stage"
  • Therapy in the Paroxysmal Stage is purely supportive