34-Haemophilus and Related Bacteria

Question 1

Haemophilus- gram stain

Answer 1

a) Gram negative rods present on human mucus membranes.

Question 2

What are the growth factor requirements for Haemophilus?

Answer 2

a) Haemophilus species require both Factor X (hemin) and Factor V (NAD). These factors are present in Chocolate agar, therefore Haemophilus grows only on chocolate agar.

Question 3

What is type b Haemophilus influenzae?

Answer 3

a) The b in H. influenzae type b refers to one of six antigenic serotypes (a - f). The serotype is determined by the strains surface antigens. Types a – f are capsulated.
b) Prior to H. influenzae b vaccine 95% of infections were because of the b serotype. Now, b/c of the vaccine, the majority of infections are caused by non-typeable and non-capsulated strains.

Question 4

What is the main virulence factor in type B?

Answer 4

Capsule

Question 5

What is the effect of the vaccination for H. influenzae infections?

Answer 5

i) Since the introduction of the vaccine in 1987, cases of H. influenzae type B in infants 2 months+ have dropped from 20,000 to about 15 per year in the USA but worldwide (between other countries) infant deaths are around 700,000 still.

Question 6

Capsulated H. influenzae- clinical presentations

Answer 6

ii) They are the strains that cause the serious illnesses, usually in babies to children
(1) Meningitis
(2) Epiglottitis
(3) Cellulitis
(4) Arthritis

Question 7

Non-capsulated H. influenzae- clinical presentations

Answer 7

i) Non-capsulated H. influenzae are present in respiratory tract of most people, but may travel elsewhere in the body and cause illnesses usually in children but seen in adults and elderly.
(1) Otitis: ear infections
(2) Sinusitis: sinus infection
(3) Lower Respiratory Tract Disease: usually seen in elderly

Question 8

Pastrurella multocida- lab features

Answer 8

a) Pasteurella multocida are gram-negative coccobacilli and are facultative anaerobic (therefore oxidase positive), and fermentative. It grows well on Chocolate but not MacConkey.

Question 9

P. multocida- transmission

Answer 9

a) Since P. multocida is found in the oropharynx of healthy animals, it is spread via animal contact (bites, scratches, shared food)