Haemophiles

Question 1

What are some general characteristics of haemophilus ?

Answer 1

• tiny gram (-) rods (cocco bacillary)
• require growth factors (x and v factor)
• fastidious aerobes (specific nutritional needs)

Question 2

What is x factor ?

Answer 2

hemin from hemoglobin
- comes from RBCs
- is heat stable (can resist heat)

Question 3

What is v factor ?

Answer 3

nicotinamide adenine dinucleotide (NAD)
- coenzyme in production of ATP
- heat labile (heat will destroy it)
- also contained in RBCs

Question 4

Where is v factor found in ?

Answer 4

yeast extract, staph and Neisseria species

Question 5

On what types of agar do we see the maximum grow of haemophilus ?

Answer 5

rabbit and horse blood agar

Question 6

On what agar does haemophilus not grow on and why ?

Answer 6

sheep blood agar plate (BAP)
- also has v inhibiting substance that makes v factor unavailable

Question 7

What factors are on sheep blood agar plates (BAP) ?

Answer 7

both X and V factor
- also has v inhibiting sustance

Question 8

What factors are on rabbit and horse blood agar ?

Answer 8

both X and V factor
- doesn’t have V inhibiting substance
- not commonly used in lab as its less stable then sheep BAP

Question 9

What type of agar is most commonly used in for isolating haemophillus ?

Answer 9

chocolate agar (heated BAP)

Question 10

What factors are required for H. influenzae growth ?

Answer 10

both X and V

Question 11

How can we grow haemophilus on a sheep agar plate ?

Answer 11

by using the satellite test/method

Question 12

How do you perform a satellite test on sheep BAP ?

Answer 12

• streak bacteria you suspect is haemophilus then make a heavy/thick streak of S. aureus over it then incubate and look for growth

Question 13

Where is the growth of haemophilus going to be found with a satellite test and why ?

Answer 13

only in the hemolytic zone (where RBS lysis has occured) that is along the S. aureus line
- V inhibiting factor is gone in the hemolytic zones because the S. aureus has destroyed it and v factor is produced in these areas

Question 14

What is chocolate agar ?

Answer 14

variant of BAP containing RBCs that have been lysed by heating
- kills RBCs and releases X and V factor for RBC
- destroyed V inhibiting substance
- changes blood color to chocolate color

Question 15

What is the factor test for Haemophilus ?

Answer 15

Tryptic Soy Agar (TSA) plate
- identification of type of haemophilus

Question 16

What is the Tryptic Soy Agar (TSA) plate ?

Answer 16

basic nutrient agar with no growth factors
- you put discs impregnated with X, V, and XV factors onto the plate
- examine growth around the disc

Question 17

How do you perform the factor test ?

Answer 17

• spread bacteria first on plate, get paper discs that are impregnated with X, V, and XV factor, then incubate for 24 hrs and look for growth
• whereever there is growth is the factor the bacteria need to grow

Question 18

What factors are needed for growth of H. influenzae ?

Answer 18

both XV

Question 19

What factors are needed for growth of H. parainfluenzae ?

Answer 19

V factor
- as long as it has V factor in to
(V factor, XV)

Question 20

What infections are caused by H. influenzae ?

Answer 20

• meningitis
• pneumonia (after viral pneumonia)
• epiglottitis (often fatal)
• pink eye (most common- contagious)

Question 21

What infections are caused by H. parainfluenzae ?

Answer 21

rarely seen as pathogens
- normal throat flora

Question 22

What are some characteristics of H. influenzae ?

Answer 22

• both X and V factor to grow
• small greyish colonies on Choc agar
• no growth of pure culture on Sheep Blood Agar
• shows growth of pure culture on Choc agar
• tiny gram (-) rods

Question 23

What are some characteristics of H. parainfluenzae ?

Answer 23

• requires at least V factor
• small greyish colonies on Choc agar
• tiny gram (-) rods
• no growth on sheep blood agar

Question 24

How is the Beta Lactamase test done ?

Answer 24

• PCN is suspended in broth
• bacteria placed in suspension
• Is bacteria possesses beta lactamase, penicillin is broken down into penicilloic acid which causes a drop in pH

Question 25

What do the results of the beta lactamase mean ?

Answer 25

detected by color change of the broth
- originally pink/red
- if acid is yellow= positive for beta lactamase enzyme
- if acid is pinkish red color= negative for beta lactamase

Question 26

What is the importance if a strain has beta lactamase ?

Answer 26

the enzyme (beta lactamase) breaks apart penicillin (PCN), rendering PCN treatment useless
- PCN interferes with cell wall production of bacteria