Biochemical tests

CATALASE TEST

Written by MicroDok

Catalase test test is used to identify microorganisms that produce catalase enzyme. It is used to differentiate catalase-producing organisms (e.g. Staphylococcus species) from non-catalase producing bacteria (e.g. Streptococcus species). Catalase enzyme breakdown hydrogen peroxide (H2O2) to water and oxygen.

2H2O2 ———> catalase ———>> 2H2O + O2

Most aerobic bacteria produce possess catalase enzyme in varying amounts except the lactic acid bacteria which do not produce the enzyme in detectable amounts. Obligate anaerobes are usually catalase negative. Hydrogen peroxide is a highly toxic product of certain cellular processes such as the reduction of flavoproteins, thus catalase test is used to determine whether or not a particular microorganism produces catalase (the enzyme that catalyzes the breakdown of H2O2). This test can be performed by two methods: the slide method and the test tube method, but only the slide method shall be expanded here.

      Procedure

  1. Perform this test with pure culture from culture media plate (preferably BA).
  2. Place a loopful or speck of the test organism on a clean glass slide.
  3. Emulsify the culture with a loopful of freshly prepared H2O
  4. Lookout for the release or presence of bubbles which indicates a catalase positive result. The bubbles results from the production of oxygen gas released from theaction of catalase enzyme (produced by the test organism) on the H2O2.

Illustration of catalase test

REFERENCES

Cheesbrough M (2006). District Laboratory Practice in Tropical Countries. 2nd Cambridge University Press, UK. Pp. 178-187.

Willey J.M, Sherwood L.M and Woolverton C.J (2008). Harley and Klein’s Microbiology. 7th ed. McGraw-Hill Higher Education, USA.

Woods GL and Washington JA (1995). The Clinician and the Microbiology Laboratory. Mandell GL, Bennett JE, Dolin R (eds): Principles and Practice of Infectious Diseases. 4th ed. Churchill Livingstone, New York.

World Health Organization (1993). Laboratory Biosafety Manual, 2nd edn. Geneva: WHO.

World Health Organization (2003). Guidelines for the Safe Transport of Infectious Substances and Diagnostic Specimens.  WHO/EMC/97.3. Geneva: WHO.

About the author

MicroDok

Leave a Comment