Podcast
Questions and Answers
What type of media is preferred for the culture of Haemophilus ducreyi?
What type of media is preferred for the culture of Haemophilus ducreyi?
- Blood agar
- Mannitol salt agar
- Chocolate agar (correct)
- Nutrient agar
Which of the following statements about meningococcal infections is true?
Which of the following statements about meningococcal infections is true?
- Haemophilus aegyptius is associated with Brazilian purpuric fever. (correct)
- Meningococcal infections are caused by Haemophilus aphrophilus.
- The symptoms of Haemophilus aphrophilus infections are exclusively gastrointestinal.
- Ceftriaxone is effective for treating infections caused by Haemophilus ducreyi.
Which of the following treatment options is NOT effective for chancroid caused by Haemophilus ducreyi?
Which of the following treatment options is NOT effective for chancroid caused by Haemophilus ducreyi?
- Intramuscular Ceftriaxone
- Oral erythromycin
- Oral trimethoprim-sulfamethoxazole
- Intravenous vancomycin (correct)
Which identifying characteristic is associated with Haemophilus aegyptius infections?
Which identifying characteristic is associated with Haemophilus aegyptius infections?
In the clinical investigation of Haemophilus infections, which specimen is least likely to yield positive results?
In the clinical investigation of Haemophilus infections, which specimen is least likely to yield positive results?
What is the major virulence factor of Haemophilus influenzae?
What is the major virulence factor of Haemophilus influenzae?
Which of the following serotypes of Haemophilus influenzae is most commonly associated with invasive disease?
Which of the following serotypes of Haemophilus influenzae is most commonly associated with invasive disease?
What type of immune response does the anti-PRP antibody facilitate?
What type of immune response does the anti-PRP antibody facilitate?
What is the recommended method to prevent Haemophilus influenzae type b disease in children?
What is the recommended method to prevent Haemophilus influenzae type b disease in children?
Which factor is necessary for the growth of Haemophilus influenzae in culture?
Which factor is necessary for the growth of Haemophilus influenzae in culture?
What age group shows the peak incidence of invasive disease caused by Haemophilus influenzae type b?
What age group shows the peak incidence of invasive disease caused by Haemophilus influenzae type b?
How does Haemophilus influenzae primarily spread among individuals?
How does Haemophilus influenzae primarily spread among individuals?
What consequence can occur due to the absence of anti-PRP antibody?
What consequence can occur due to the absence of anti-PRP antibody?
Flashcards
Haemophilus species
Haemophilus species
A group of small, gram-negative, pleomorphic bacteria that require enriched media for growth. They are found in the mucous membranes of the upper respiratory tract.
Haemophilus influenzae
Haemophilus influenzae
Commonly found in the mucous membranes of the upper respiratory tract in humans. They are small, aerobic, pleomorphic gram-negative cocco bacilli.
Polysaccharide capsule
Polysaccharide capsule
The outer layer of a bacterial cell, composed of polysaccharides, providing protection against host defenses.
Serotypes of Haemophilus Influenzae
Serotypes of Haemophilus Influenzae
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Type b capsule of Haemophilus influenzae
Type b capsule of Haemophilus influenzae
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Growth requirements of Haemophilus influenzae
Growth requirements of Haemophilus influenzae
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Anti-PRP antibody
Anti-PRP antibody
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Why children between 5 months and 5 years are particularly vulnerable to Haemophilus influenzae
Why children between 5 months and 5 years are particularly vulnerable to Haemophilus influenzae
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Haemophilus aegyptius conjunctivitis
Haemophilus aegyptius conjunctivitis
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Haemophilus ducreyi
Haemophilus ducreyi
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Chocolate Agar
Chocolate Agar
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Blood Culture for Haemophilus
Blood Culture for Haemophilus
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Microscopy for Haemophilus Infections
Microscopy for Haemophilus Infections
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Study Notes
Haemophilus Species Overview
- Haemophilus species are small, gram-negative, pleomorphic bacteria.
- They require enriched media for growth.
- Includes H. influenzae, H. ducreyi, H. aegyptius, and H. aphrophilus.
Haemophilus influenzae
- Found in the upper respiratory tract of humans.
- Aerobic, small, pleomorphic gram-negative coccobacilli.
- Contains a polysaccharide capsule.
- Six serotypes (a-f) based on capsular polysaccharide antigenicity.
- Type b is responsible for 95% of invasive diseases.
- Type b capsule composed of polyribitol phosphates.
- Unencapsulated/untypeable strains can cause sinusitis and otitis media.
- Growth requires heme (X factor) and nicotinamide adenine dinucleotide (NAD) (V factor).
- Infects only humans.
- Adhesion, colonization, cell damage, and impaired ciliary function are steps in invasion.
- IgA1 protease facilitates colonization.
- Lipid A (from LPS) causes meningeal inflammation.
- Can enter the bloodstream (bacteremia) and spread to meninges.
- Pathogenesis involves anti-phagocytic capsule and endotoxin; no exotoxin.
- Key virulence factor: antiphagocytic polysaccharide capsule (PRP).
- Maternal antibodies provide protection (enhance phagocytosis & complement-mediated bacteriocidal activity).
- Absence of anti-PRP antibody can lead to invasion, bacteremia.
- Peak incidence in children aged 5 months to 1 year.
- Transmission is person-to-person via respiratory route.
- Prevented by Haemophilus b conjugated vaccine.
Haemophilus aegyptius
- Formerly known as Koch-Weeks bacillus.
- Associated with highly contagious conjunctivitis.
- Causes Brazilian purpuric fever in children (fever, purpura, shock, death).
Haemophilus aphrophilus
- Associated with infective endocarditis and pneumonia.
- Part of the normal oral and respiratory tract flora.
Haemophilus ducreyi
- Causes chancroid (sexually transmitted disease).
- Characterized by ragged genital ulcers and swelling.
- Requires X factor but not V factor.
- Treatable with antibiotics (ceftriaxone, trimethoprim-sulfamethoxazole, erythromycin).
Clinical Investigations
- Specimens: Oral swabs (avoid contamination), lower respiratory tract sputum, direct needle aspiration, cerebrospinal fluid (CSF), blood (bacteria count >107/ml).
- Microscopy: Gram-negative bacilli in CSF (before antibiotic treatment) in >80% cases.
- Culture: Chocolate agar preferred (enriched media) with added X and V factors.
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