Biochemical Tests for Bacterial Identification

By Acharya Tankeshwar •  Updated: 05/03/22 •  2 min read

In this blog post, I am sharing information about common, conventional biochemical tests and their primary uses in the Microbiology laboratory for the identification of pathogens of interest. Some of the biochemical tests mentioned here for example catalase test, oxidase test assist us in many ways apart from the primary purpose mentioned in this post;

Beta-glucuronidase test (MUG Test)

MUG test is used to identify Escherichia coli. Escherichia coli produces the enzyme β-D-glucuronidase, which hydrolyzes β-D-glucopyranosid-uronic derivatives to aglycons and D-glucuronic acid.

Overview of Biochemical tests for differentiating Gram positive cocci
Overview of Biochemical tests for differentiating Gram positive cocci

Bacitracin Sensitivity Test

Bacitracin sensitivity test differentiates Streptococcus pyogenes (positive) from other beta-hemolytic streptococci (resistant).

Bile solubility test

Bile solubility test is used to differentiate Streptococcus pneumoniae from other alpha-hemolytic streptococci. Bile or a solution of bile salt, such as sodium desoxycholate rapidly lyses pneumococcal colonies.

CAMP Test
CAMP test :
A. Streptococcus agalactiae (positive)
B. Streptococcus pyogenes (Negative)
Image Source: ASM

CAMP Test

Certain organisms such as Streptococcus agalactiae (Group B streptococci), produce a diffusible extracellular protein (CAMP) factor that acts synergistically with the beta-lysin of Staphylococcus aureus and causes enhanced lysis of RBCs.

Catalase test

Catalase test is used to differentiate Staphylococci (catalase-positive) from Streptococci (catalase test negative)

Citrate utilization test

To differentiate members of the Enterobacteriaceae family.

Coagulase test

Coagualse test is used to identify Staphylococcus aureus. Coagulase test differentiates Staphylococcus aureus (positive) from coagulase-negative staphylococci (CONS), such as S. epidermidis, S. saprophyticus.

DNase test

This test is used to determine the ability of an organism to hydrolyze DNA. It is primarily used to identify Staphylococcus aureus.

Indole test

This test is used to determine the ability of an organism to split tryptophan to form the compound indole. It is used to differentiate gram-negative rods particularly E. coli in a microbiology laboratory.

Litmus milk decolorization test

To help identify Enterococcus and some Clostridia which have the ability to metabolize litmus milk.

Lysine Decarboxylase test

To assist in the identification of Salmonella and Shigella

Oxidase test

To help identify Neisseria, Pasteurella, Vibrio, and Pseudomonas. This test is used to determine the presence of bacterial cytochrome oxidase.

Urease test

Urease test is used to determine the ability of an organism to produce urease (an enzyme) that hydrolyzes urea. This test is done to help identify Proteus, Morganella, Yersinia enterocolitica, and Helicobacter pylori.

Acharya Tankeshwar

Hello, thank you for visiting my blog. I am Tankeshwar Acharya. Blogging is my passion. As an asst. professor, I am teaching microbiology and immunology to medical and nursing students at PAHS, Nepal. I have been working as a microbiologist at Patan hospital for more than 10 years.

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33 responses to “Catalase test: Principle, Procedure, Results, Uses”

  1. Thimantha says:

    Very good explanation

  2. Bawade Raymond says:

    i am really impressed and have also learned a lot from your write up.
    It made me passed excellently my microbiology end of semester exams.

  3. ayaat nsaar says:

    hello my work on ornithobacterium rhinotracheale bacteria. I want any helpful information about its isolation and identification

    • Diriba says:

      I have the following question for you
      1. Is all salmonella species are catalase positive
      2. What are biochemical test use for the differentiation of salmonella and cetrobacter youngae

  4. Sohaib Afzaal says:

    I want to check the growth of bacteria in the presence of methylene blue 0.1 %. but I am not confirmed about the formulation to make the media. I need your kind help. Thank You

  5. Angel says:

    Hello,Kindly let me know whether it was an error when you wrote that the positive control for catalase test is staphylococcus aureus instead of staphylococcus species.Kindly clarify, because I know coagulase test is done to identify staphylococcus aureus

    • tankeshwar says:

      The best practice is to use known strain during Quality Control procedure and most researchers prefer/use ATCC strains. If you have Staphylococcus aureus, it can also be used as a positive control for Catalase test but it’s not mandatory, you can use any species of Staphylococci for this purpose.

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