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Questions and Answers
A splenectomized patient is at increased risk of sepsis from which of the following organisms?
A splenectomized patient is at increased risk of sepsis from which of the following organisms?
- Streptococcus pneumoniae
- Escherichia coli
- Haemophilus influenzae (correct)
- Staphylococcus aureus
Which virulence factor is produced by Haemophilus influenzae to facilitate colonization of the upper respiratory tract?
Which virulence factor is produced by Haemophilus influenzae to facilitate colonization of the upper respiratory tract?
- Streptokinase
- IgA protease (correct)
- Protein A
- Hyaluronidase
What is the most likely cause of epiglottitis, a life-threatening condition due to airway obstruction, in unvaccinated children?
What is the most likely cause of epiglottitis, a life-threatening condition due to airway obstruction, in unvaccinated children?
- Type B _Haemophilus influenzae_ (Hib). (correct)
- Unencapsulated _Haemophilus influenzae_.
- _Moraxella catarrhalis_.
- _Streptococcus pneumoniae_.
Which of the following diagnostic tests is LEAST useful for identifying meningitis caused by Haemophilus influenzae from a CSF sample?
Which of the following diagnostic tests is LEAST useful for identifying meningitis caused by Haemophilus influenzae from a CSF sample?
What is the underlying mechanism by which the Hib conjugate vaccine has curtailed invasive Haemophilus influenzae type B infections in children?
What is the underlying mechanism by which the Hib conjugate vaccine has curtailed invasive Haemophilus influenzae type B infections in children?
Why can Haemophilus influenzae grow on chocolate agar but not on standard blood agar?
Why can Haemophilus influenzae grow on chocolate agar but not on standard blood agar?
What is the recommended treatment for a patient with a severe systemic infection caused by Haemophilus influenzae?
What is the recommended treatment for a patient with a severe systemic infection caused by Haemophilus influenzae?
What is the most critical step in the prevention of invasive diseases caused by Haemophilus influenzae type b (Hib) in young children?
What is the most critical step in the prevention of invasive diseases caused by Haemophilus influenzae type b (Hib) in young children?
A patient with COPD presents with pneumonia. Which of the following organisms is a likely causative agent?
A patient with COPD presents with pneumonia. Which of the following organisms is a likely causative agent?
Why are unencapsulated strains of Haemophilus influenzae more often associated with upper respiratory tract infections such as otitis media and sinusitis?
Why are unencapsulated strains of Haemophilus influenzae more often associated with upper respiratory tract infections such as otitis media and sinusitis?
Flashcards
Haemophilus influenzae Characteristics
Haemophilus influenzae Characteristics
Gram-negative coccobacillus requiring Factor X (heme) and Factor V (NAD) for growth on chocolate agar. It has 6 serotypes based on capsular polysaccharides.
Hib Vaccine
Hib Vaccine
A highly effective vaccine containing purified PRP antigen conjugated to a protein carrier, drastically reducing systemic infections in young children.
Upper Respiratory Infections
Upper Respiratory Infections
Infections include otitis media, sinusitis, conjunctivitis, and potentially life-threatening epiglottitis. Unencapsulated strains and bronchopneumonia are often the cause.
Meningitis Symptoms
Meningitis Symptoms
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Lab Diagnosis of H. influenzae
Lab Diagnosis of H. influenzae
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Treatment of H. influenzae Infections
Treatment of H. influenzae Infections
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Study Notes
- Haemophilus influenzae used to be a leading cause of meningitis in young children.
- Systemic infections in children younger than 5 years old were virtually eliminated due to effective conjugate vaccines.
- Current H. influenzae infections in the U.S. primarily occur in unvaccinated children and elderly adults with waning immunity.
- A highly effective conjugate vaccine contains purified PRP (polyribosylribitol phosphate) antigen to reduce the incidence of disease.
- Conjugation to diphtheria toxoid, administered to children between 2 and 18 months old, reduced meningitis incidence by 90%.
- H. influenzae causes upper respiratory tract infections, including otitis media, sinusitis, conjunctivitis, and life-threatening epiglottitis.
- Unencapsulated strains cause upper respiratory tract infections and bronchopneumonia.
- Infections cause pain in the affected area, opacification of the infected sinus, and redness with bulging of the tympanic membrane.
- H. influenzae causes pneumonia, especially in COPD patients.
- It is a Gram-negative coccobacillus with a polysaccharide capsule, and has 6 serotypes.
- It grows on chocolate agar with growth factors like Factor X (heme) and Factor V (NAD) for energy.
- Type B (Hib) causes severe diseases like meningitis, septic arthritis, and cellulitis.
- Meningitis symptoms include fever, headache, stiff neck, and drowsiness.
- It's commonly found in the upper respiratory tract, colonizing by producing IgA protease.
- Transmission occurs through inhalation of droplets.
- Sepsis is more likely in splenectomized patients.
- Diagnosis involves culturing blood, CSF, or synovial fluid, which grows on chocolate agar with Factors X and V but not on blood or MacConkey agar.
- H. influenzae is catalase and oxidase positive.
- Meningitis diagnosis from CSF samples includes Gram staining, capsular quellung reaction, and immunofluorescent staining.
- Capsular antigen can be detected by latex agglutination, countercurrent immunoelectrophoresis, ELISA, and radioimmunoassay.
- Treatment for meningitis or serious systemic infection includes ceftriaxone or cefotaxime.
- Treatment for upper respiratory tract infections includes trimethoprim-sulfamethoxazole or ampicillin + clavulanate.
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