Pertussis pathophysiology
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Aditya Govindavarjhulla, M.B.B.S. [2]
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Overview
Pertussis is primarily a toxin-mediated disease. Bordetella pertussis attaches to the cilia of the respiratory epithelial cells, proliferates and produces virulence factors that paralyze the cilia, and causes inflammation of the respiratory tract, which interferes with the clearing of pulmonary secretions.[1]
Pathophysiology
Pathogenesis
- Bordetella pertussis has tropism for pulmonary tissue and rarely disseminates to other organs.
- The steps involved in the pathogenesis of pertussis include the following:
- Inoculation
- Attachment to the respiratory epithelium
- Proliferation
- Production of virulence factors (toxins)
- Evasion of host immune cells
- Tissue destruction
Virulence Factors
Bordetella pertussis produces multiple antigenic and biologically active virulence factors responsible for the clinical manifestations of pertussis. These virulence factors include:[1]
- Pertussis toxin (PT)
- PT undergoes ADP-ribosylation of G proteins to disrupt signal transduction in host cells.
- Filamentous hemagglutinin (FHA)
- Suface protein responsible for the interaction and adhesion between host cells and Bordetella pertussis.
- FHA is a component of the acellular DTaP vaccine.
- Agglutinogens
- Adenylate cyclase toxin (ACT)
- ACT delivers an adenylate cyclase domain into the host cell and increases the intracellular cAMP concentration.
- Following cAMP delivery, phagocyte activity is inhibited and undergo apoptosis.
- Pertactin (PRN)
- PRN defends Bordetella pertussis against the host neutrophil (immunomodulation).
- PRN is a component of the acellular DTaP vaccine.
- Tracheal cytotoxin
- TCT is responsible for the death of host respiratory cells
- Fimbriae (FIM)
- Surface appendages to adhere to host cells and avoid host immune cells (immunomodulation).
- FIM is a component of the acellular DTaP vaccine.
- Humans are the only reservoir for Bordatella pertussis, and the incubation period varies from 1 to 3 weeks, and is usually about 10 days. Although asymptomatic carriers have been reported, they have a low probability of transmitting the disease as they are not actively coughing. Pertussis is highly contagious, and highest rates of transmission occurs with exposure to the infected individual at 5 feet or less.
- Infection occurs through direct contact with the aerosolized mucus of infected persons, usually during coughing and sneezing. The bacterium adheres to the ciliated epithelium of the nasopharynx and proliferates in the lower respiratory system. In addition, the bacterium produces toxins that paralyze the cilia, and cause inflammation of the respiratory tract, which interferes with the clearing of pulmonary secretions.
- In a small number of cases, the bacteria may move further to the pulmonary alveoli, causing Bordatella pneumonia. The bacteria does not however cross the respiratory epithelium to the bloodstream, and therefore sepsis is not seen.