Bordetella

Bordetella is a genus of gram negative coccobacilli, which are encapsulated. They are non-motile except B. bronchiseptica and are obligate aerobes except B. petrii. They are highly fastidious.

Pathogenesis

Route of entry
Bordetella infects only humans and is transmitted by air borne droplets.

• Capsule is antiphagocytic
• Organism produces pigment
• Hemaggluttinin, facilitates attachment to the cilia of the epithelial cells of the respiratory tract.
• Adenylate cyclase is taken up by phagocytic cells and inhibits their bactericidal activity.
• Pertussis-toxin inhibits signal transduction by chemokine receptors, therefore lymphocytes cannot enter lymphoid tissue.
• This stimulates adenylate cyclase by catalyizing ADP-ribosylation of inhibitory submit of G-proteins complex (Gx).
• Toxin also binds to receptors on the surface of the respiratory tract epithelial cells.

Virulence factors
• Filamentous hemagglutinin
• Pertussis toxin
• Adenylate cytotoxin
• Capsule

Predisposing factors
• Infants and young children
• Immunocompromised

Clinical symptoms
• Whooping cough
• Severe paroxysmal cough (1-4 week)

• Series of hacking coughs
• Massive amounts of mucus

• Leukocytosis up to 70%
• Exhaustion due to cough
• Pneumonia

Lab- Diagnosis

Specimen
• Nasopharyngeal secretions collected by aspiration
• Per nasal swab

Microscopy
• Gram negative coccobacillus
• Non-motile
• Capsulated

Culture
• Strict aerobes

Charcoal cephalexin blood agar
Small pearly grey, shiny, mucoid colonies are formed.

Biochemical tests

• Urease negative
• Does not reduce nitrate
• Oxidase positive

Serological tests

• Fluorescent- antibody staining
• PCR

Treatment

• Erythromycin
• Oxygen therapy
• Suction of mucus