Haemophilus Influenzae Flashcards
Characteristics of Haemophilus Influenzae
● It has nothing to do with influenza
● Pleomorphic, Gram (-ve) coccobacilli
Haemophilus Influenzae is divided into
● Capsulated strains (typable strains) =more severe
● Non-capsulated strains (nontypeable strains)
➢Diseases caused by capsulated strains of Haemophilus Influenzae
- Meningitis
- Epiglottitis
♦️3. Community acquired pneumonia
- Septic Arthritis
Epiglottitis (CASE)
● Fever
● Sore throat
♦️● Drooling of the saliva
● Cherry Red epiglottis
● Catcher Stand
➢Diseases caused by non-capsulated strains
- Otitis media
- Conjunctivitis
- Sinusitis
- Mastoiditis
- Cellulitis (characteristic periorbital cellulitis)
- Hospital acquired pneumonia
➢Transmission of Haemophilus
Aerosol transmission via respiratory droplets.
➢Pathogenesis Haemophilus
● H. influenzae type B is the most virulent (severe) serotype because it has:
- Antiphagocytic capsule: type b capsule is composed of polyribitol phosphate (PRP)
- Pilli: for attachment
- IgA protease: breaks down secretory IgA thus facilitating attachment to the respiratory mucosa
- Beta-lactamase
From the nasopharynx, where it causes invasion and colonisation, it enters the bloodstream causing bacteremia and then it migrates and affects the site it reaches
➢Predisposing Factors of Haemophilus Influenzae
- Splenectomy (because capsulated bacteria are destroyed in the spleen)♦️
- Immunodeficiency
- Sickle cell anemia
- Seasonal variations (leads to viral infections-> decrease the immunity
-> predispose to other bacterial infections)
➢Diagnosis of Haemophilus Influenzae
- Specimen collection:
● Meningitis-> CSF
● Epiglottitis -> swab (or blood)
- Microscopy: Gram (-ve) coccobacilli
- Culture (it’s fastidious):
● Chocolate agar + Factor V (NAD+) and Factor X (Hemin)
● Exhibits sattelitism. Larger zone of hemolysis when added to Staphylococcus Aureus in the same culture.
- Biochemical tests:
● Quellung reaction of the capsule and Latex agglutination test
● Oxidase (+ve)
● Catalase (+ve)
- PCR
اي بكتریا بتعمل Meningitis وعندھا capsule بتعمل لیھا الحاجات المشتركة دي
➢Treatment Haemophilus Influenzae
● Meningitis-> Ceftriaxone
● Epiglottitis-> Co-trimoxazole
➢Prevention:✍️
● Isolation then vaccination
● Vaccine -> Conjugated HiB Vaccine. It’s a capsular polysaccharide vaccine.
● Meningitis in close contacts of the patient can be prevented by Rifampin. (side effects include orange discoloration of tongue)
● Other types of Haemophilus and test for differentiation
- Haemophilus Ducreyi:
Causes Chancroid. They are painful ulcers at the genital area (the ulcer of Syphilis is painless) “You do cry with Ducreyi!”
- Haemophilus Aegyptius: Causes conjunctivitis (pink eye)
- Haemophilus Parainfluenzae
- Haemophilus Aphrophilus
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Tests for factors X and V:
- Grows in both X and V:
Haemophilus Influenzae and Haemophilus Aegyptius
- Grows in X only: Haemophilus Ducreyi
- Grows In V only:
Haemophilus Parainfluenzae
