Biochemical identification of bacterial isolates

Biochemical identification of bacterial isolates


Biochemical tests are used for the identification of bacteria. These are based on the different biochemical reactions taking place in different bacteria. It is often called biotyping. Similarly, identification on the basis of the antigenic characteristics of bacteria is called serotyping.


  1. Bacterial culture
  2. Antisera
  3. Biochemicals
  4. Catalase reagent
  5. Oxidase reagent
  6. Slides
  7. Inoculating loops
  8. Nutrient agar plates
  9. Peptone water


  1. Incubator
  2. Laminar air flow
  3. Bunsen burner


  1. Inoculate the culture to be identified on nutrient agar plate and incubate at 37°C overnight.
  2. Note down the colony characteristics and pick up at least four to five colonies of similar morphology and inoculate in peptone water. Incubate peptone water at 37°C for 3 – 4 hours.
  3. By that time pick up the growth and perform catalase and oxidase test and note down the results.
  4. Select the biochemicals to be used for the identification on the basis of colony morphology and results of catalase and oxidase tests.
  5. Arrange the biochemicals in a rack and inoculate them with the inoculated peptone water (step 2).
  6. Incubate the biochemicals at 37°C overnight.
  7. Next day note down the results and compare them with identification charts to identify the organism.
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