Haemophilus and Bordetella Flashcards
What are the general physical properties of Haemophilus influenzae? (size, shape, gram, motility)
Small, gram-negative, non-motile, non-spore-forming bacilus/coccobacilus (pleimorphic)
What are the two categories of Hemophilus influenzae?
Encapsulated (typeable) and Unincapsulated (non-typeable)
What disease do encapsulated strains of H. influenzae cause?
acterial meningitis in young children
What disease do unencapsulated strains of H. influenzae cause?
ear aches and respiratory disease
Which type of encapsulated H. influenzae is the most important pathogen? What makes it different?
Type B has ribose instead of hexose in its polysaccharide capsule
Is the capsule of encapsulated H. influenzae required for virulence? What purpose does it serve?
Yes, it is antiphagocytic
What are the common clinical presentations of H. influenzae infection? (3 main types of infection with their presentations)
- Nasopharyngitis often with otitis media. Can spread with bacteremia and meningitis
- Epiglottitis with obstructive laryngitis - May be FATAL within 24hrs
- Cellulitis and childhood pyarthrosis or pneumonia
How does H. influenzae enter the body?
via respiratory tract generally through aerosols between children
What does H. influenzae do to evade the immune system and prevent being expelled from the respiratory tract? (2 things)
- Has an IgA protease
2. Induces ciliary stasis through decoration of LPS with host choline
When is the most susceptible period in a person’s life (age)? How long does resistance remain low.
Most susceptible period between 6-12 months of age; resistance remains low for the first few years of life
Is there a vaccine for Haemophilus influenzae? If so, what type of vaccine is it?
Yes, a conjugate capsular vaccine made with polyribosyl phosphate (PRP) linked to diptheria toxoid
What are the treatment options for H. influenzae meningitis?
- 3rd generation cephalosporin
- Augmentin (ampicillin + clavulanate) - if the organism proves to be b-lactamase negative, treatment is switched to ampicillin
What are the typical clinical manifestations of infections with NON-TYPEABLE H. influenzae? (2 common, 2 less common)
Common: 1. Otitis media 2. conjunctivitis
Less common 1. respiratory tract infections (usu. underlying respiratory condition) 2. meningitis (usu. a predisposing factor, important in neonates)
Is haemophilus purely an extracellular pathogen?
No, it can invade mammalian cells
Is there a vaccine for non-typeable H. influenzae? If so, what type is it?
No, there is no vaccine for non-typeable H. influenzae
What are the treatment approaches for otitis media and sinusitis caused by H. influenzae?
- Amoxicillin
2. Clavulanate or ceftriaxone
How does non-typeable H. influenzae avoid killing by antibiotics?
It forms antibiotic resistant biofilms and can invade cells
What type of growth conditions does H. influenzae require? (ie: does it need oxygen, are there any other factors it requires to be successfully grown in medium)
Faculative anaerobe
Requires growth factors X (hemin) and V (NADP), both present in blood
What type of agar plate must be used to culture H. influenzae? Why?
Chocolate agar must be used because the mild heat used in preparation releases factors X and V from RBC
How is the growth of staphylococcus related to the growth of H. influenzae?
Staph releases sufficient factor V to support growth of H. influenzae on blood agar plates
What is the appearance of colonies of encapsulated H. influezae on medium?
Grow as smooth colonies
If you suspect meningitis due to H. influenzae in your patient, how will you confirm your diagnosis? (What labs will you draw? What types of tests will you do?)
- Draw blood and spinal fluid for culture
- Streak spinal fluid on chocolate agar and incubate in CO2
- Use immunofluorescence/immunoelectrophoresis to detect type b capsular Ag in spinal fluid
What are the clinical manifestations of infection with Haemophilus ducreyi?
chancroid on genetalia
What are the treatment options for a patient with a chancroid caused by Haemophilus ducreyi?
Sulfonamides, tetracycline, streptomycin
What is the clinical manifestation of infection with Haemophilus aegypticus?
conjunctivitis, especially in hot climates (southern U.S.)
What are the clinical manifestations of infection with Haemophilus parainfluenzae?
pharyngitis and bacterial endocarditis - major component of micro flora of oral and upper respiratory tract
What major disease does Bordetella pertussis cause?
whooping cough
What is the general physical structure of Bordetella pertussis? (size, gram, shape, oxygen utilization)
Small, gram-negative, coccobacillus, obligate aerobe
In what animals is Bordetella pertussis found?
Only in humans
What is the incubation period of B. pertussis?
7-10 days
What clinical symptoms characterize the catarrhal stage of B. pertussis infection?
runny nose, sneezing, low-grade fever, and mild occasional cough (cold symptoms)
What clinical symptoms characterize the paroxysmal stage of infection with B. pertussis?
bursts of coughing followed by high-pitched whoop and occasional vomiting with narrowing of the glottis following prolonged coughing fits
How is B. pertussis introduced into the body?
via water droplets
During the multiplication and toxin production stage of B. pertussis infection, do organisms invade the bloodstream?
No, they remain in the respiratory tract
What are the 4 toxins produced by B. pertussis?
- Pertussis toxin
- Adenylate cyclase toxin
- Dermonecrotic toxin
- Tracheal cytotoxin
What type of toxin is pertussis toxin and how does it act?
ADP-ribosylating toxin that affects a G-protein involved in inhibition of adenylate cyclase thus leading to an accumulation of cAMP
Also affects the control of phospholipase C and ion channels
What are the combined impacts of pertussis toxin?
lymphocytosis, sensitization to histamine, enhancement of insulin secretion
How does adenylate cyclase toxin act and what is its effect?
It is activated by endogenous calmodulin.
It catalyzes the production of cAMP from ATP
Results in supraphysiologic concentrations of cAMP that impairs leukocyte function and may cause cell death
Which Bordetella pertussis toxin is also known as “mouse lethal toxin” or “heat-labile toxin”?
Dermonecrotic toxin
What does Dermonecrotic toxin cause?
It causes vascular smooth muscle contraction resulting in ischemic necrosis of lung tissue
What does tracheal cytotoxin cause?
It causes ciliostasis, inhibits DNA synthesis, and ultimately kills tracheal epithelial cells
What is the physical impact of the Pili of Bordetella pertussis on the host?
Pili mediate attachment to ciliated epithelial cells of the upper respiratory tract and cause diminished ciliary activity
Other than Pili, what are the other 2 structures participating in colonization of Bordetella persussis?
filamentous hemagglutinin and pertactin
Does the pertussis vaccine produce life-long immunity
No
What is the main advantage of the DTaP vaccine over the DTP vaccine for pertussis?
The DTaP vaccine contains an acellular pertussis component so it is less likely to produce encephalopathy
B. pertussis requires ____ _____ media for growth, so most clinical labs have switched to using PCR to detect organisms from washes of the nasal cavity.
very fresh
What is the drug of choice for infection with B. pertussis? What are the alternatives?
Erythromycin; Alternatives: tetracycline, chloramphenicol
What are the common diagnostic tests for B. pertussis?
Gram stain nasopharyngeal swab; direct anti-body test; culture on B-G
