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Microbiology > Haemophiles > Flashcards

Haemophiles Flashcards

1
Q

What are some general characteristics of haemophilus ?

A
  • tiny gram (-) rods (cocco bacillary)
  • require growth factors (x and v factor)
  • fastidious aerobes (specific nutritional needs)
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2
Q

What is x factor ?

A

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

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3
Q

What is v factor ?

A

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

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4
Q

Where is v factor found in ?

A

yeast extract, staph and Neisseria species

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5
Q

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

A

rabbit and horse blood agar

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6
Q

On what agar does haemophilus not grow on and why ?

A

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

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7
Q

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

A

both X and V factor
- also has v inhibiting sustance

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8
Q

What factors are on rabbit and horse blood agar ?

A

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

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9
Q

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

A

chocolate agar (heated BAP)

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10
Q

What factors are required for H. influenzae growth ?

A

both X and V

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11
Q

How can we grow haemophilus on a sheep agar plate ?

A

by using the satellite test/method

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12
Q

How do you perform a satellite test on sheep BAP ?

A
  • streak bacteria you suspect is haemophilus then make a heavy/thick streak of S. aureus over it then incubate and look for growth
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13
Q

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

A

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

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14
Q

What is chocolate agar ?

A

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

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15
Q

What is the factor test for Haemophilus ?

A

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

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16
Q

What is the Tryptic Soy Agar (TSA) plate ?

A

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

17
Q

How do you perform the factor test ?

A
  • 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
18
Q

What factors are needed for growth of H. influenzae ?

A

both XV

19
Q

What factors are needed for growth of H. parainfluenzae ?

A

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

20
Q

What infections are caused by H. influenzae ?

A
  • meningitis
  • pneumonia (after viral pneumonia)
  • epiglottitis (often fatal)
  • pink eye (most common- contagious)
21
Q

What infections are caused by H. parainfluenzae ?

A

rarely seen as pathogens
- normal throat flora

22
Q

What are some characteristics of H. influenzae ?

A
  • 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
23
Q

What are some characteristics of H. parainfluenzae ?

A
  • requires at least V factor
  • small greyish colonies on Choc agar
  • tiny gram (-) rods
  • no growth on sheep blood agar
24
Q

How is the Beta Lactamase test done ?

A
  • 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
25
Q

What do the results of the beta lactamase mean ?

A

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

26
Q

What is the importance if a strain has beta lactamase ?

A

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

Microbiology (18 decks)

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