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BACTERIAL IDENTIFICATION

Gram positive bacteria
1. Catalase test
  1. Use to identify organisms that produce enzyme catalase.
  2. This enzyme detoxifies hydrogen peroxide to produce water and oxygen gas.
2. Mannitol Salt Agar (MSA)
  1. MSA will select orgnisms which can live in high salt concentration
  2. Organisms capable of using mannitol as a food source will produce acidic byproducts of fermentation
  3. Acid will cause the pH indicator, phenol red, to turn yellow
3. Coagulase test
  1. Coagulase is an enzyme that clots blood plasma
  2. Coagulase is a virulence factor of some Gram positive bacteria
  3. The formation of clot around an infection caused by this bacteria likely protects it from phagocytosis
Gram negative bacteria
1. Oxidase test
  1. This test is used to identify microorganisms containing the enzyme cytochrome oxidase
  2. Cytochrome oxidase transfers electrons from the electron transport chain to oxygen and reduces it to water
  3. In the oxidase test, artificial electron donors and acceptors are provided. When the electron donor is oxidized by cytochrome oxidase it turns a dark purple
2. Motility agar
  1. Used to determine whether an organism is equipped with flagella and thus capable of swimming away from a stab mark
  2. If the entire tube is turbid, this indicates that the bacteria have moved away from the stab mark
3. Urease test
  1. This test is used to identify bacteria capable of hydrolyzing urea using the enzyme urease
  2. The hydrolysis of urea forms the weak base, ammonia, as one of its products
  3. This weak base raises the pH of the media above 8.4 and the pH indicator, phenol red, turns from yellow to pink

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BACTERIAL IDENTIFICATION

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	Created by Syafiq Aizat about 8 years ago