PE - Tests to be performed by the students!

Question 1

Wet-mount

Answer 1

• Sample -> slide -> cover -> look

Question 2

Preparation and fixation of smears with cotton wool swabs and/or loop from broth and/or plate

Answer 2

• degreaszetion by heat
• drop of liquid culture to the slide OR drop 1 saline + inoculation loop sample
• fixation by heat
• stain

Question 3

Clumping (rabbit plasma)

Answer 3

• the clumping factor present on Staphyloccocus areus will will convert fibrinogen to fibrin => the bacteria cocci will stick to each other. (looks like agglutination)

Question 4

Oxidase reaction

Answer 4

Add oxidase reagent -> add bacteria:
- Positive: pink / purple / blue

(Pseudomonas, Neisseria, Vibrio, Campylobacter)

Question 5

Catalase reaction

Answer 5

2 H2O2 –> 2 H2O + O2
Adding few drops of hydrogen-peroxide to isolated bacteria:
- Positive: bubbles
- Negative: Nincs bubbles

Question 6

Indole

Answer 6

Triptophane -> indol (triptophanase enzyme)

Amylalcoholic (=organic) reagent -> indol is dissolved here after mixing -> intensive red ring on top (alcohol is lighter then water!)
can be performed in ureum- indol tube

Indole positive bacteria: E.coli, Klebsiella, proteus, shigella