Bordetella Study Notes

Bordetella Overview

  • Classification: Gram-negative bacilli, small, obligate aerobes.
  • Growth Characteristics: Do not ferment carbohydrates; can be less fastidious than previously thought.

Key Species of Bordetella

  • Major Pathogens:
    • Bordetella pertussis (causes whooping cough, more severe).
    • Bordetella parapertussis (milder form of infection).
  • Other Species: Bordetella bronchioseptica (opportunistic pathogen), Bordetella avium, Bordetella hinzii, etc.

Disease Description

  • Pertussis (Whooping Cough): Highly contagious respiratory infection, primarily affects children.
    • Transmission: Aerosolized droplets from human to human.
    • Infectivity: 90% infection rate upon exposure to susceptible individuals.
    • Symptoms: Catarrhal phase (flu-like symptoms), paroxysmal phase (violent coughing), convalescent phase (recovery with risk of secondary infections).

Virulence Factors

  • Attachment: Filamentous hemagglutinin (FHA) and pertactin.
  • Toxins: Pertussis toxin (exotoxin causing systemic effects), adenylate cyclase toxin (inhibits immune responses), and tracheal toxin (causes ciliary paralysis).

Vaccination

  • DPT Vaccine: Comprises components for diphtheria, tetanus, and pertussis.
    • Types: Acellular (less adverse effects but shorter protection) and whole-cell (more protective).
  • Need for Boosters: Vaccination does not confer lifelong immunity; adults need boosters, particularly if around infants to prevent transmission.

Laboratory Diagnosis

  • Specimen Collection: Posterior nasopharynx swab, transport in appropriate media (e.g., charcoal horse blood agar).
  • Culture Characteristics: Bordetella grows slowly, requiring specialized media; looks like mercury drops on agar.
  • Identification Tests: Urease test distinguishes spp. (B. pertussis is urease negative, B. parapertussis positive).
    • PCR Testing: Preferred modern method for rapid diagnosis.

Treatment and Sensitivity

  • Antibiotics: Erythromycin and sulfa drugs are effective against B. pertussis and B. parapertussis; bronchioseptica requires sensitivity testing for treatment.
  • Prophylaxis: Recommended if exposure suspected during catarrhal phase to prevent disease development.