Bordetella Flashcards
Bordetella Morphology/staining:
Gram-negative
Aerobic coccobacilli
Tiny
Bordetella is found in the ______ tract.
Found in the respiratory tract
Bordatella culture:
Strict aerobe
Non-motile
Non-spore forming
Catalase positive
Why is Bordatella difficult to grow?
Sensitive to drying
Susceptible to toxic metabolites that are produced by the bacteria as they grow on the plate
Bordatella media:
Requires agar supplemented with charcoal, starch, blood, or albumin that absorbs toxic substances and metabolites
B. pertussis virulence factors:
No polysaccharide capsule
Pertactin and filamentous hemagglutinin (Fha)
Toxins are major virulence factor:
Pertussis toxin (PT)
Adenylate cyclase toxin
Bordetella mechanism of infection:
Affects distal respiratory tract epithelium (trachea and bronchial tree) where ciliary movement is fairly important
Filamentous hemagglutinin attached to the cilia on the surface of the respiratory tract cells
Toxin production helps mediate ciliary stasis. The loss of ciliary movement helps facilitate persistence of the bacterial infection in the bronchial tree
Describe function of the pertussis toxin subunits:
A subunit catalyzes ADP ribosylation of a cellular regulatory protein (G- protein) which prevents inactivation of adenylate cyclase
B subunit binds to receptors on ciliated respiratory cells and phagocytic cells
How is pertussis toxin released:
Released by the organism at the surface of the cell, gets endocytosed, and blocks a protein that inhibits production of cAMP leading to increased cAMP levels.
Biologic effects of pertussis toxin:
Increased respiratory secretions
mucus production
lymphocytosis
Describe the function and mechanism of adenylate cyclase toxin:
Causes increased cAMP levels in host cells
Interferes with chemotaxis and superoxide production of leukocytes
Results in increased respiratory secretions and swelling in the respiratory epithelium
Transmission of Bordetella pertussis
Spread by respiratory droplets and highly infectious
Only human pathogen; no other reservoir
Typical demographic of B. pertussis:
Most common and severe in infants from birth to 2 years
Mechanism of transmission of B. pertussis from adults to infants:
Adults can have an asymptomatic infection (subclinical or milder clinical disease) making them a major reservoir of spread to infants who have more severe disease
4 stages of pertussis infection:
Incubation
Catarrhal
Paroxysmal Cough
Convalescent
Length and symptoms of pertussis incubation stage:
Incubation - 7-10 days
No symptoms
Length and symptoms of pertussis Catarrhal stage:
Lasts 1 - 2 weeks
Characterized by rhinorrhea, malaise, fever, sneezing, anorexia
Length and symptoms of pertussis Paroxysmal cough stage:
Cough up to 50 times a day for 2-4 weeks
Inspiratory whoop, vomiting, mucoid secretions, marked lymphocytosis (common)
Length and symptoms of pertussis Convalescent stage:
Lasts 3-4 weeks
Cough gradually fades, development of secondary complications
In which stage is pertussis usually diagnosed?
Paroxysmal Cough Stage
What are the secondary complications of pertussis and when do they occur?
Pneumonia (S. pneumoniae), atelectasis, convulsions, hemorrhage following Convalescent stage
Most effective treatment of B. pertussis and when is it most effective?
Macrolide treatment; only effective in catarrhal stage, not the paroxysmal stage
Modes of diagnosis for B. pertussis:
Culture nasopharyngeal sample on charcoal Regan-Lowe media
Nucleic acid (PCR) testing of Nasopharyngeal specimen
Only beneficial in the early catarrhal stage
Nucleic acid (PCR) testing of a nasopharyngeal specimen is only beneficial in the early \_\_\_\_\_\_\_ stage of pertussis for diagnosis.
Nucleic acid (PCR) testing of a nasopharyngeal specimen is only beneficial in the early catarrhal stage of pertussis for diagnosis.
