Bordetella

Characteristics/Epidemiology

Human pathogens: Bordetella pertussis, Bordetella parapertussis.

Survives only briefly outside human respiratory tract

Affect children 1-5. Very young children are protected to some extent by maternal antibodies.

Serotyped on the basis of cell-surface molecules 'agglutinogens'.

Pathogenesis/Transmission

Transmission: droplets by coughing

Binds to ciliated epithelium in upper respiratory tract

1. Pertussis toxin

Major virulence factor

Cause:

• lymphocytosis
• sensitisation to histamine
• activation of insulin-secreting islet cells (leading to hypoglycemia

2. Filamentous hemagglutinin

Facilitate attachment to ciliated epithelial cells in respiratory tract

3. Adenylate cyclase toxin

Adenylate cyclase, which is taken up by leukocytes

-> increase in intracellular cAMP

-> interference with leukocyte function

4. Dermonecrotic toxin

Causes vasoconstriction and ischaemic necrosis

5. Tracheal cytotoxin

Inhibits cilia movement

Prevents regeneration of damaged cells

6. Agglutinogens

Contribute to attachment to host cells

Clinical significance

Whooping cough (Pertussis)

Phase 1: Incubation

1-3 weeks

Phase 2: Catarrhal phase

Nonspecific symptoms

• rhinorrhoea
• mild conjunctival hyperemia
• malaise
• mild fever

Progress to dry non-productive cough

Phase 3: Paroxysmal phase

Paroxysms of coughing

   -> may be associated with cyanosis/vomiting

Elevation in WBC in late catarrhal phase or early paroxysmal phase

Phase 4: Convalenscence

3-4 weeks.

Complications

Infections e.g. otitis media, pneumonia

CNS dysfunction e.g. encephalopathy, seizure

Laboratory identification

Microscopic

• Aerobic
• Encapsulated coccobacilli (grow singly or in pairs)

Cultured on selective agar (containing blood and charcoal, and antibiotics to inhibit other growths)

Diagnosis can be made on clinical grounds on paroxysmal cough.

Serologic test for antibodies to B. pertussis

Treatment

First line: erythromycin

Second line: trimethoprim/sulfamethoxazole

Supportive treatment

Prevention/immunity

Prophylaxis for close contacts: erythromycin

Vaccination

2 forms of vaccine

• Killed whole cells
• Acelluar, with purified proteins

Immunisation starts at 2 month old.

 

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