AAT Bioquest

What are the steps of streaking techniques in microbiology?

Posted September 18, 2023


Streaking techniques are used to obtain a pure bacterial culture from a mixed culture. There are 6 types of streaking techniques in microbiology. Although each technique is unique in some form, they all use the same basic steps. 

  1. All instruments and flasks required for the procedure are thoroughly cleaned and sterilized. 
  2. Refrigerated samples and media are allowed to come to room temperature. 
  3. The work area is cleaned and disinfected to minimize contamination. 
  4. The Bunsen burner is set up carefully in the work area.   
  5. The petri dish is labeled with key details noted including the date, culture being inoculated, media used, and researcher’s name. 
  6. A metal loop or disposable plastic loop is used to pick up the sample, which is streaked in a back-and-forth motion on the first quadrant of the agar plate. 
  7. The other three quadrants are streaked in a similar manner. If using a metal loop, it is sterilized between picking up samples. If using disposable loops, a new loop is used to pick up different samples. 
  8. The lid of the plate is closed after streaking and the dish is stored upside down in an incubator that is maintained at optimal temperature (usually 37C). 

After the incubation period of 24 hours, the terminal streaks are observed for isolated colonies. 

Additional resources

Manual versus automated streaking system in clinical microbiology laboratory: Performance evaluation of Previ Isola for blood culture and body fluid samples

Cell Sample Preparation

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