Hemophilus

Question 1

What are the general characteristics of Haemophilus species?

Answer 1

• Small, pleomorphic, Gram-negative rods (coccobacilli)
• Non-motile, oxidase positive
• Facultative anaerobes, fermentative
• Requires enriched media like chocolate agar with X and V factors for growth
• Grows better in CO₂-enriched conditions

Question 2

What are the main pathogenic species of Haemophilus?

Answer 2

• H. influenzae: primary human pathogen, type b (Hib) is the most virulent
• H. ducreyi: causes chancroid, an STD
• Other species include H. parainfluenzae and H. aegyptius

Question 3

What are the growth requirements for H. influenzae?

Answer 3

• Requires both X (hemin) and V (NAD) factors
• Cultured on chocolate agar
• Growth is better under CO₂-enriched conditions

Question 4

What are the main virulence factors of H. influenzae type b?

Answer 4

• Capsule: Polysaccharide capsule with PRP, key for invasiveness
• IgA Protease: Degrades IgA, helping colonization
• Adhesion Factors: Pili and non-pilus adhesins for oropharynx attachment
• LPS: Causes inflammation, impairing ciliary function

Question 5

What are the main clinical diseases caused by H. influenzae?

Answer 5

• Invasive (usually by Hib): Meningitis, epiglottitis, pneumonia, cellulitis, septic arthritis
• Non-invasive (often non-typeable): Otitis media, sinusitis, conjunctivitis

Question 6

What is the epidemiology of H. influenzae?

Answer 6

• Human reservoir, primarily in the nasopharynx
• Transmitted via respiratory droplets or direct secretion contact
• Non-capsulated strains commonly colonize healthy people
• Hib was a major invasive pathogen before vaccination

Question 7

How is H. influenzae diagnosed in the lab?

Answer 7

• Specimens: CSF, blood, sputum, joint fluid
• Microscopy: Gram stain for coccobacilli
• Culture: Chocolate agar, CO₂ incubation
• Antigen Detection: Latex agglutination for PRP, Hib detection
• PCR: High specificity, useful for rapid confirmation

Question 8

What are the treatment options for H. influenzae infections?

Answer 8

• Severe infections: Ceftriaxone or cefotaxime
• Less severe: Amoxicillin, azithromycin, clarithromycin
• Beta-lactamase-producing strains resist ampicillin

Question 9

What are the prevention strategies for H. influenzae type b (Hib)?

Answer 9

• Vaccination: Hib vaccine with conjugated PRP
• Prophylaxis: Rifampin for close contacts
• Vaccination has reduced Hib invasive disease globally