Question

• What is the catalase test? Coagulase test?  
• What does it mean to be:
  • Catalase +
  • Catalase -
  • Coagulase +
  • Coagulase -

When working with an unknown that may be Staphylococcus (but you are not sure), how can the two tests help?

Give step by step detail of how to determine you are dealing with Staphylococcus and not an organism such as Streptococcus (next week topic).

Give step by step details on how to determine you are dealing with:

• S. epidermidis
• S. aureus

Please answer completely all of the above, only typed responses with works cited rated, thanks!

Answer 1

Catalase test:

Answer: Catalase test is a specific biochemical test used to determine the presence of catalase enzyme in bacteria, the catalase enzyme releases the oxygen after the catalysis of hydrogen peroxide.

Coagulase test:

Answer: Coagulase test is a specific biochemical test used to determine the presence of coagulase enzyme in bacteria, the coagulase enzyme converts the soluble fibrinogen into insoluble fibrin to form an insoluble clot in plasma.

Catalase +: It means bacteria have an active catalase enzyme and release oxygen when the drop of hydrogen peroxide added in bacterial culture.

Catalase -: It means bacteria does not have an active catalase enzyme and does not release oxygen when the drop of hydrogen peroxide added in bacterial culture.

Coagulase +: It means bacteria have an active coagulase enzyme and converts the soluble fibrinogen into insoluble fibrin to form an insoluble clot in plasma when bacterial culture added in plasma.

Coagulase -: It means bacteria does not have an active coagulase enzyme and does not able to converts the soluble fibrinogen into insoluble fibrin to form an insoluble clot in plasma when bacterial culture added in plasma.

When working with an unknown that may be Staphylococcus (but you are not sure), how can the two tests help?

Give step by step detail of how to determine you are dealing with Staphylococcus and not an organism such as Streptococcus (next week topic).

Answer: The catalase test is used to differentiate in between Staphylococci and Streptococci. Staphylococci are catalase-positive whereas Streptococci are catalase-negative. Because of both Staphylococci and Streptococci are gram-positive circular bacteria. The coagulase test is used to identify the Staphylococcus aureus from other Staphylococcus like S. epidermidis.

Give step by step details on how to determine you are dealing with:

1. First, we perform the gram staining to determine the morphology and staining property of bacteria and observe under a microscope - it shows gram-positive circular or oval bacteria.

Results: the bacteria may be a Staphylococci or Streptococci

2. After that, we perform the catalase test, if bacterial culture shows: a. Catalase positive - the bacteria may be a Staphylococci, b. Catalase negative - the bacteria may be a Streptococci

3. If culture is Staphylococci then we perform the Coagulase test, if bacterial culture shows: a. Coagulase positive - the bacteria may be an S. aureus, b. Coagulase-negative - the bacteria may be an S. epidermidis

Reference:

Karen Reiner 2010. Catalase Test Protocol, Laboratory Protocols, American Society for Microbiology.

D. Sue Katz2010.Catalase Test Protocol, Laboratory Protocols, American Society for Microbiology.