Bordetella Pertussis Flashcards

Bordetella Pertussis: Detailed Overview

Bordetella is a family of microorganisms that causes disease in both humans and animals.
The most important organism in this family is Bordetella pertussis, which causes whooping cough (pertussis).
Parapertussis, a cousin of Bordetella pertussis, causes a milder infection compared to pertussis, similar to how parainfluenza relates to influenza.
In severe cases, pertussis predominantly affects the bronchioles, posing a significant risk of death to young infants due to necrosis in the bronchioles.
In adults, pertussis typically presents as laryngitis or bronchitis, leading to a chronic nagging cough.

On Gram stain, Bordetella appears as a coccobacillus, potentially more coccoid than Haemophilus.
It is a slow-growing organism, often outgrown by other respiratory organisms on standard HBA and chocolate agar plates.
Selective media is required to culture Bordetella, with growth taking around five days.
Due to the slow growth, many labs do not attempt to culture the organism, which is detrimental for studying changes in the organism and potential vaccine escape.
Cultures of Bordetella pertussis on Bordet-Gengou medium show raised, pearly-looking colonies described as "bisected pearls."

Bordetella pertussis is highly infectious and spreads quickly through communities, especially with poor vaccination coverage.
It is purely a human-carried organism.
Infectiousness is highest during the catarrhal stage.
Secondary attack rates are high, indicating a significant risk of transmission to individuals in close proximity to infected persons.
Children under two months of age are at the greatest risk of death from pertussis.

Bordetella pertussis effectively destroys ciliated cells through various mechanisms.
Destruction of cilia impairs mucus clearance, allowing the organism to grow and kill cells.
The organism modulates the host immune response, utilizing factors like surfactant A (SPA) and lipo-oligosaccharide (LOS).
LOS inhibits complement and is not recognized by surfactant A, which normally controls respiratory infections.
The organism can survive within phagocytes, limiting the effectiveness of phagocytosis.
Pertussis suppresses lymphocyte-derived immunity and antibody production, leading to poor long-term immunity.
In young children, damage extends to the bronchioles, where necrosis leads to plugs of necrotic material that interfere with oxygen exchange, often requiring hospitalization.

Filamentous Hemagglutinin (FHA):
- Agglutinates erythrocytes when separated.
- Important for adhesion and initiating invasion.
Fimbriae:
- Small, hair-like appendages on the surface of bacteria.
- Important for adhesion.
Pertactin:
- Important for cell wall adhesion.
- Assists in invasion.
Adenylate Cyclase Toxin:
- Interferes with internal cytoplasmic processes, slowing down cellular functions.
- Impairs leukocyte function.
Tracheal Cytotoxin and BTEA:
- Toxins that damage ciliated epithelial cells.
BTEA:
- Injected through a type three secretion system (think of needles injecting effector proteins).
Pertussis Toxin (PT):
- Not found in parapertussis, potentially explaining milder infections.
- An AB toxin with a binding (B) part consisting of a pentamer (five parts).

The organism attaches to cells via filamentous hemagglutinin and other surface proteins.
It injects toxins (like BTEA) using a type three secretion system.
Pertussis toxin is excreted, with the binding part (pentamer) facilitating entry and causing cellular damage.
Overall process leads to ciliary damage, reactive oxygen species production, cellular death, and cyanotoxicity.

PCR is now the primary method for pertussis identification, according to the CDC.
Serological diagnosis was previously emphasized, but pertussis is effective at suppressing antibody production, resulting in poor IgG production.
Nasopharyngeal specimens for culture must be collected within the first two weeks of coughing.

Early treatment is more effective.
Adults with chronic coughs are typically not treated.
Infants and young children are treated with azithromycin or erythromycin.
Penicillin is not effective against Bordetella.
Prophylaxis is given to household contacts, especially when infants are at risk.

Vaccination is the most important means of preventing pertussis.
Falling vaccination rates, often due to anti-vaccination messaging, result in infants being hospitalized.
Vaccine protection lasts approximately five years, necessitating revaccination, especially for individuals in households with new babies.
The current acellular vaccine is an improvement over previous vaccines, minimizing side effects and encouraging vaccination.
Understanding and promoting childhood vaccination schedules is crucial for microbiologists.