(III) Fastidious Gram Negative Rods (6)* Haemophilus spp.

Question 1

What shape is H. influenzae?

Answer 1

Coccobacillus

Question 2

Characterize the growth medium required to grow H. influenzae

Answer 2

(1) Chocolate agar
(2) + Factor V
(3) + Factor X

Question 3

What is another name for Factor V (used in H. influenzae growth medium)?

Answer 3

Nicotinamide

(V ∝ Nickle = “Nickle-tinamide”)

Question 4

What is another name for Factor X (used in H. influenzae growth medium)?

Answer 4

Hematin

(“Heme-a-ten”)

Question 5

ROT: H. influenzae

Answer 5

Aerosol transmission

Question 6

Name 3 infections caused by H. influenzae

Answer 6

(1) Epiglottitis
(2) Otitis media
(3) Meningitis

Question 7

Describe what the epiglottis looks like in epiglottitis

Answer 7

“Cherry red epiglottis”

(Epiglottitis is associated ⇒ so-called “thumbprint sign” on x-ray)

Question 8

Which strains of H. influenzae can cause meningitis?

Answer 8

Those with B capsular antigen

Question 9

Name a gram (-) respiratory bacteria that sickle cell patients are at increased risk for

Answer 9

H. influenzae

(∵ Functionally asplenic + capsule)

Question 10

What antigen do you develop immunity to after receiving the H. influenzae vaccine?

Answer 10

B capsular antigen

(This is opposite to Neisseria where you get immunity to all antigens EXCEPT B)

Question 11

How is the immunigenicity of H. influenzae’s capsular antigen increased?

Answer 11

Conjugated to Diphteria toxoid

Question 12

When should H. influenzae vaccine be given?

Answer 12

2-18 months

(∵ Very young children are most at risk of meningitis due to H. influenzae. Also, not a live vaccine, so we can give prior to 1 year)

Question 13

Treatment: Meningitis due to H. influenzae

Answer 13

Ceftriaxone

Question 14

What antibiotic is used prophylactically to those exposed to meningitis causing strain of H. influenzae

Answer 14

Rifampin

Question 15

H. Influenzae’s growth is both […] and […] dependent, but H. Ducreyi is only […] dependent

Answer 15

H. Influenzae’s growth is both X (haem) and V(NAD) dependent, but H. Ducreyi is only **X (haem) **dependent

“Haemophilus means “blood loving.” This organism requires a blood-containing medium for growth. **Hematin (X) **found in blood is necessary for the bacterium’s cytochrome system. Blood also contains NAD+ (V) , needed for metabolic activity.”

H. Influenzae wont survive around x or v tablet. It can only survive around XV tablet.

Question 16

Haemophillus ducreyi infection

Histology: […]

Transmission: […]

Classic Clinical Presentation
[…]

Answer 16

Haemophillus ducreyi infection

Histology: Shoal of Fish appearance

Transmission: Sex

Classic Clinical Presentation
Chancroid: painful genital ulcer + enlarged unilateral inguinal lymph nodes that may ulcerate and suppurate

The clinical presentation is very impt to differentiate it from syphilis (painless), **HSV1&2 **(has systemic symptoms) and Chlamydia trachomatis LGV (painless) infections.

PCR can identify all of these at once!

Question 17

Haemophillus influenzae infection (IMPT!!!)

Transmission: […]

Virulence Factor: Some strains possess […] (although in SG the most common type is the non- encapsulated type)

What are the clinical presentations for diff strain types of H Influenzae Inflection?
1. Encapsulated strain infections (common amongst children):
[…]

2. Non-encapsulated strain infections:
   […]

Answer 17

Haemophillus influenzae infection (IMPT!!!)

Transmission: Respiratory droplet, close contact

Virulence Factor: Some strains possess antiphagocytic capsule (although in SG the most common type is the non- encapsulated type)

What are the clinical presentations for diff strain types of H Influenzae Inflection?
1. Encapsulated strain infections (common amongst children):
- meningitis
- acute epiglottitis (use of tongue depressor can cause acute respiratory obstruction due to laryngeal spasm)
- septicaemia
- cellulitis
- pneumonia
- osteomyelitis, septic arthritis

2. Non-encapsulated strain infections:
   - invasive (meningitis & septicaemia in neonates; pneumonia in older age groups)
   - non-invasive (local upper respiratory tract infections like otitis media, sinusitis, infective exacerbation of COPD, conjunctivitis)

Majority of invasive disease is due to non-encapsulated strains now!

Some strains produce BL so can only use ampicillin for severe infections if reported as ‘S’. Otherwise, ceftriaxone reliably effective.

“It takes 3-5 years of Haemophilus infiuenzae colonization and infection for children to develop their own antibodies. So there is a window during which children are sitting ducks for the invasive Haemophilus infiuenzae.”

Presentation includes everything from GBS???

Question 18

The historically important H.Influenzae serotype that has a vaccine for it? (IMPT!!!!)
[…]

Answer 18

The historically important H.Influenzae serotype that has a vaccine for it? (IMPT!!!!)
Serotype B, Hib (H. influenzae serotype B) vaccine

Type b was commonly associated with invasive Haemophilus influenzae disease in children, such as meningitis, epiglottitis, and septic arthritis .

Question 19

What is the HACEK group?

[…]

Who are the members in the HACEK group?

H[…]
A[…]
C[…]
E[…]
K[…]

Answer 19

What is the HACEK group?

a group of slow-growing fastidious GNR known to cause endocarditis

Who are the members in the HACEK group?

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

Investigate pt for endocarditis if any of the HACEK group is found present in a blood culture