Pertussis (B)

What environmental conditions exist that microbes/potential pathogens deal with?

• must survive in the respiratory tract, particularly the trachea and cilliated epithelial surfaces

What is/are the mechanism(s) of pathogenesis?

• B. Pertussis attaches to ciliated tracheal cells using adhesins

• interferes with the ciliary escalator, stopping normal mucus clearance

• survives inside phagocytes, evading immune defenses

• toxins increase mucus production, damaging tissues, and immobilize cilia

• pertussis progresses through four phases: incubation → catarrhal → paroxysmal → convalescent

How do they damage the hosts?

• destruction of ciliated epithelial cells in the trachea

• toxin activity causing:

  • increased mucus production

  • inhibition of leukocyte movement and phagocytosis

  • hemorrhage and cell death

  • paralyzing or stopping ciliary motion

• results in severe coughing spells, oxygen limitation, cyanosis, vomiting, and exhaustion

Is the damage due to toxicity, invasiveness, or both?

Both

• toxicity: multiple toxins directly damage cells and interfere with immune function

• invasiveness: bacteria attach, survive inside phagocytes, and persist in the respiratory tract

What are the virulence factors (generally speaking)?

• adhesins

• toxins

• ability to survive within phagocytes

• interference with ciliary function

What virulence factors are associated with the pathogens above?

• adhesins

  • filamentous hemagglutinin

  • pertussis toxin (also acts as toxin)

• Toxins

  • pertussis toxin

  • adenylate cyclase toxin

  • dermonecrotic toxin

  • tracheal cytotoxin

• other factors

  • survival within phagosomes

  • inducing human cells to make more receptors for attachment

How are the pathogens transmitted?

• through the air in respiratory droplets

• highly contagious

What is the mode of infection?

• inhalation of droplets containing B. pertussis

• bacteria enter via the respiratory tract

What is the source?

• source is infected humans (airborne droplets)

• No reservoir outside humans

What are the symptoms of these diseases?

• early (catarrhal): rhinorrhea, sneezing, malaise, fever

• later (paroxysmal):

  • severe, repetitive coughing spells

  • “whoop” sound during inhalation

  • vomiting

  • exhaustion

  • possible cyanosis

  • ruptured eye blood vessels

• Convalescent: gradual reduction of coughing

What is the progression of the disease?

1. incubation (1week)

   1. No symptoms

2. Catarrhal (2-3weeks)

   1. Rhinorrhea, sneezing, malaise, fever

   2. highly contagious

3. Paroxysmal (3-6weeks)

   1. repetitive coughing fits (40-50/day)

   2. whooping inhalation

   3. vomiting and exhaustion

   4. possible cyanosis

4. Convalescent (6-10weeks)

   1. cough gradually diminishes

   2. possible secondary infections