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