Aerobic Gram+ Rods

Question 0

What is the principle of the catalase test?

Answer 0

H2O2 converted to H2O and O2 in the presence of catalase.

Question 1

New aerobic gram positive cocci. First test?

Answer 1

Catalase test

Question 2

How is a catalase test performed?

Answer 2

On a slide: 1 drop of 3% H2O2 on a colony.

In a tube: 1 ml 3% H2O2 on an overnight culture slant.

Question 3

What are the results of a catalase test?

Answer 3

Positive: bubbles, lots of bubbles.
Negative: no bubbles.

Question 4

What does a positive catalase test on a gram positive aerobic rod colony indicate?

Answer 4

The colony may be Bacillus, Cornyebacterium, Listeria, Mycobacteria, Nocardia, or Streptomyces.

Question 5

What does a negative catalase test on a gram positive aerobic rod colony indicate?

Answer 5

The colony is Erisipelothrix or Lactobacillus.

Question 6

gram positive aerobic rods, positive catalase. What next?

Answer 6

Examine the colonies. Are they large and forming spores? Then determine a Bacillus species.

Do the rods branch? It is Streptomyces or Nocardia. We haven’t covered them yet.

Otherwise it is Bacillus Cornyebacterium , Listeria or Mycobacteria.
Otherwise it is