Catalase and coagulase test

                                   Coagulase test

This test is used to identify S. aureus which produces the enzyme coagulase.

Principle:

Coagulase causes plasma to clot by converting fibrinogen to fibrin.

Two types of coagulase are produced by most strains of S. aureus:-

Ø  Free coagulase which converts fibrinogen to fibrin by activating a coagulase-reacting factor present in plasma. Free coagulase is detected by clotting in the tube test.

Ø  Bound coagulase (clumping factor) which converts fibrinogen directly to fibrin without requiring a coagulase reacting factor. It can be detected by the clumping of bacterial cells in the rapid slide test.

A tube test must always be performed when the result of a slide test is not clear, or when the slide test is negative and Staphylococcus has been isolated

from a serious infection. A tube test may be required to detect some MRSA (methicillin resistant S. aureus) strains although some commercially available latex test kits to differentiate coagulase positive and coagulase negative staphylococci, overcome this. Before performing a coagulase test, examine a Gram stained smear to confirm that the

organism is a Gram positive coccus.

Required:

EDTA anticoagulated human plasma (preferably pooled and previously HIV and hepatitis tested) or rabbit plasma. The plasma should be allowed to warm to room temperature before being used.

Bacteria are Coagulase-positive?

Coagulase-positive staphylococci include not only Staphylococcus aureus but also S. intermedius and S. hyicus; some strains from each of these species are known to produce enterotoxin.

Bacteria are Coagulase-negative?

Coagulase-negative staphylococci (CoNS) are a type of staph bacteria that commonly live on a person's skin. Doctors typically consider CoNS bacteria harmless when it remains outside the body. However, the bacteria can cause infections when present in large amounts, or when present in the bloodstream.

                                 

catalase test 

The catalase test is used to differentiate staphylococci (catalase-positive) from streptococci (catalase-negative). The enzyme, catalase, is produced by bacteria that respire using oxygen, and protects them from the toxic by-products of oxygen metabolism.

Bacteria are catalase positive?

Staphylococci and Micrococci are catalase-positive. Other catalase-positive organisms include Listeria, Corynebacterium diphtheriae, Burkholderia cepacia, Nocardia, the family Enterobacteriaceae (Citrobacter, E. coli, Enterobacter, Klebsiella, Shigella, Yersinia, Proteus, Salmonella, Serratia), Pseudomonas, Mycobacterium tuberculosis, Aspergillus, Cryptococcus, and Rhodococcus equi

Bacteria are catalase negative?

If no bubbles appear, the bacteria are catalase negative. Staphylococcus and Micrococcus spp. are catalase positive, whereas Streptococcus and Enterococcus spp. are catalase negative.

Difference between catalase and coagulase test

Catalase is an enzyme that converts hydrogen peroxide to water and oxygen gas. ... This test assays for the presence of coagulase, an enzyme that coagulates blood plasma, and can differentiate between Staphylococcus aureus (coagulase positive) and Staphylococcus epidermidis (coagulase negative).