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13 Cards in this Set
- Front
- Back
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Name the diseases caused by H. influenzae?
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Bronchitis, sinusitis, pneumonia, otitis media, epiglottitis, bacterial meningitis.
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What is the morphology of H. influenzae?
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Encapsulated gram negative pleomorphic coccobacillus
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What special culture requirements does H. influenzae have?
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Chocolate agar with factors V(NAD, nicotinamide adenine dinucleotide) and X (hematin). H. influenzae forms satellite colonies on blood agar near Staph aureus because S. aureus hemolyzes RBCs releasing factors V and X.
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What are the virulence factors of H. influenzae?
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Capsule(6 serotypes), LPS, attachment factors(pili, fibrils, protein hemophilus influenzae adhesin, immunoglobulin A(IgA) protease.
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What is u nique about capsule serotype B of H. influenzae?
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Associated with invasive infections in children. B capsule is composed of repeating polyribosylribitol phosphate(PRP, pentose sugars), other serotypes have hexose sugars.
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How is H. influenzae diagnosed?
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Culture in chocolate agar with factors V and X and latex agglutination against PRP.
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What is the H. influenzae vaccine composed of?
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The haemophilus influenzae type B(Hib) vaccine is made of type B capsular polysaccharide conjugated to a protein(diphtheria toxoid) that allows for a T-dependent immune responses providing greater protection than T-independent immune response.
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H. influenzae is known for causing epiglotittis in children. How does this present?
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An initial sore throat with fever that progresses to airway obstruction, stridor dysphagia and drooling due to an inability to swallow. The epiglottis is red and swollen.
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Why has H. influenzae remained the second most common cause of otitis media in children vaccinated with Hib?
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90% of Otitis media is caused by a nonencapsulated(nontypeable) type, thus antibodies against type B are not protective.
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What diseases are seen in the nonencapsulated strains versus encapsulated type-b H. influenzae?
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Nonencapsulated strains cause local infections such as pneumonia, otitis media and sinusitis. Encapsulated type B strains cause invasive infections such as meningitis, acute epiglottitis, septic arthritis and sepsis.
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Why are patients with sickle cell disease especially susceptible to H. influenzae infection?
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The spleen is necessary to clear encapsulated organisms and sickle cell disease results in autosplenectomy.
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What are the treatment options for H. influenzae?
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Local infections are treated with amoxicillin with clavulanate or 2nd or 3rd generation cephalosporin.
Invasive infections are treated with 3rd generation cephalosporins such as ceftriaxone that can cross the blood brain barrier to treat meningitis. |
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What drug is used for prophylaxis for close contacts?
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Rifampin achieves a high concentration in secretions, thereby reducing spread.
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