Haemophilus influenzae

Question 1

How to classify?

Answer 1

Fastidious gram negative coccobacillary

Question 2

What are the encapsulated invasive diseases it causes?

Answer 2

Meningitis, acute epiglottitis, septicaemia, cellulitis, pneumonia, osteomyelitis, septic arthritis

SSPOCAM

Question 3

What are the growth requirements and what does it grow on?

Answer 3

Grow better on enriched agar (chocolate agar)
X (haem dependent) and V (NAD dependent)

Question 4

What is the virulence factor?

Answer 4

Capsule (encapsulated and non-capsulated strains are invasive)
* Encapsulated: capsule types a,b,c,d,e,f (antigenically distinct polysaccharide capsules)
* Non-encapsulated (non-typable): carriage in 65% of infants

Question 5

Which type is the most important serotype?

Answer 5

Type B

Question 6

What is the vaccine called?

Answer 6

Hib

Question 7

What invasive diseases does non-encapsulated H.influenzae cause?

Answer 7

Neonatal infections (meningitis, septicaemia), pneumonia (in older pts)

majority now due to non-encapsulated strains

Question 8

What non-invasive diseases does non-encapsulated H.influenzae cause?

Answer 8

Sinusitis, otitis media, exacerbation of COPD, conjunctivitis

Question 9

What is the treatment?

Answer 9

For mild: treat in community with amoxicillin
For severe: ceftriaxone, co-amoxiclav
- Some strains produce beta-lactamase which attacks ampicillin and amoxycillin

Question 10

What is the HACEK group?

Answer 10

• H.parainfluenzae, H.aphrophilus
• Aggregatibacter
• Cardiobacterium hominis
• Eikenella corrodens
• Kingella kingae

Slow-growing fastidious GNR
If in blood culture, consider endocarditis