Haemophilus and Bordetella Flashcards
Does Haemophilus have a capsule?
No
Which strain of hemophilus is the most virulent? What distinguishes between the different strains?
Type B strains are the most virulent. They have a capsule with ribose rather than hexose sugars
What is the quellung reaction used for? How does it work?
Used to visualize the capsule of bacteria. Works by adding antibody that binds to the capsule, causing it to swell
What are Haemophilus influenza B (Hib) reservoirs?
Nasopharynx of humans
What are the complications that can arise from invasive disease of HiB?
Bacteremia Meningitis Epiglotitis Cellulitis Join infections
What toxin are we worried about with a HiB infection?
LPS endotoxin. This particular LPS is unique because it is decorated with host choline
When are infants most susceptible to Hi infection?
Between 6-12 months. Adaptive immunity develops at around 3-4 years.
Is there a vaccine to Hib? What is its structure?
Yes–very effective vaccine in place. It is a conjugate capsular Hib vaccine using synthetic carbohydrates. Must use a protein carrier to enhance immune response
What is the treatment with Hib infections?
3rd generation cephalosporins (cefotaxime, ceftrixone)
-beta lactamase inhibitor
What are the sites of infection for untypable Haemophilus?
otitis media sinusitis tracheobronchitis pneumonia Can also cause conjunctivitis
What does it mean that a strain of haemophilus is nontypable?
Does not have a capsule
Adhesins are very important to H.i. colonization. Name the adhesins that are found in typeable and nontypeable Hi
Hap
Which adhesin is found in most non-typeable H.i.s?
HMW1/2
If missing HMW1/2, will most likely have Hia
Which adhesin is primarily found in typeable Hi?
Hsf
Is untypeable H.i. an extracellular or intracellular pathogen?
Both
What are the three routes of invasion for untypeable H.I.?
macropinocytosis, paracytosis, LPS-platelet activating factor
Can you develop long term immunity to untypeable H.i? Is there a vaccine?
Strain specific. For some strains, long term immunity never develops. There is also no vaccine
How do you treat NTHi? (Non-typeable H.i.)
amoxicillin. If resistant, add a beta-lactamase inhibitor
What atmospheric growth conditions does Hi need (aerobe/anaerobe?)
facultative anaerobe
What kind of agar plate do you need to grow H.i? This is diagnostic
chocolate agar with X factor (hemin) and V factor (NAD/NADP) which is released from RBCs
Why does hemophilus influenzae usually accompany streptococcus?
Hi CANNOT lyse RBCs on its own. Needs a second pathogen to lyse cells to grant it access to necessary factors X and V
How would you diagnose HiB?
culture blood and spinal fluid on chocolate agar and perform a gram stain
Is Hi gram positive or negative? What is its morphology?
gram negative. Can alter its shape (pleiomorphic)
Is bordetella pertussis gram positive or gram negative? What morphology does it have?
gram negative. Coccobacillus
What atmospheric conditions does pertussis need to grow?
obligate aerobe!
What are pertussis reservoirs?
Humans only
What is the incubation period of bordetella pertusis?
7-10 days
Describe the steps in the infectious process for bordetella:
- water droplets
- adherence to tracheal and nasopharyngeal epithelial cells
- Multiplication
- Toxin production
- Evasion of host defenses
- Transmission
Can bordetella cause bacteremia?
No. However, the toxin can be distributed systemically
What are the exotoxins produced by bordetella?
pertussis toxin, adenylate cyclase toxin, dermonecrotic toxin
What are the endotoxins produced by bordetella?
trachael cytotoxin
endotoxin (LPS)
How does the pertussis toxin exert its effects?
Binds a Gi protein which inhibits adenylate cyclase inactivation. Constitutively active.What
- Levels of cAMP rise
- Causes lymphocytosis, increased insulin production, sensitization to histamine
S1 subunit of pertussis toxin is the catalytic subunit. What is its name?
ADP-ribosylating toxin. It targets a G-protein, inhibits adenylate cyclase, and cAMP levels rise
What do the S2-S6 subunits of the pertussis toxin do?
Aid in binding to toxin to target cells for S1 to do its magic.
What does the adenylate cyclase toxin of bordetella do?
directly catalyzes production of cAMP from ATP in the host cell cytoplasm.
What does dermonecrotic toxin (DNT) do?
Causes local necrosis and inflammation by acting on GTPase rho protein
What does tracheal cytotoxin do?
Stops cilia from beating and kills tracheal epithelial cells
What are the virulence determinant of bordetella associated with bacterial attachment?
Pili
- filamentous hemagglutinin binds galactose moieties
- pertactin surface molecule
- tracheal colonization factor
Which one of the toxins secreted by bordetella is responsible for the whooping cough?
Pertussis toxin
What were issues with the early bordetella vaccine?
Contamination with LPS. Hard to issolate only the other virulence factors
What are the components of the new pertussis vaccine?
Acellular petussis component vaccine
- Pertussis toxoid prevents symptoms. The other components prevent infection.
- Fha
- pertactin
- Fimbrae
How would you diagnose whooping cough?
PCR detection for Bordetella-specific insertion sequences (IS)
- Culture on Bordet-gengou agar with glycerol, starch, and blood (uncommon)
- Lymphocytosis
- Classic cough
How do you treat B. pertussis?
Erythromycin.
B. Pertussis is RESISTANT to ampicillin+penicillin
What are the bordetella subspecies?
B parapertussis (lacks some toxins. Similar symptoms to whooping cough) Bbronchispetica (Rare, only in immunocomprised. Can cause pneumonia)
