Standard Operating Procedure (SOP) for Growth Promotion Test

This SOP provides a United States Pharmacopoeia guideline for conducting a Growth Promotion Test. Always refer to specific pharmacopeial references and laboratory quality management system guidelines when performing the test for microbiological media used in specific applications.

This Standard Operating Procedure (SOP) outlines the steps for conducting a Growth Promotion Test (GPT) to ensure the quality and performance of microbiological media used in the laboratory.

Standard Operating Procedure (SOP) for Growth Promotion Test


To describe the procedure for the growth promotion test of Medias used in Microbiology Lab for routine testing.


Procedure is applied to incoming Medias for microbiological tests.


Manager Quality Control is responsible to ensure that procedure and formats are followed entirely as approved.
Microbiologist is responsible to conduct the test.


United States Pharmacopoeia


Growth Promotion Test: A cluster or assemblage of microorganisms growing on a solid surface such as the surface of an agar culture medium; the assemblage often is directly visible, but also may be seen only microscopically.

Standard Operating Procedure (SOP) for Growth Promotion Test

Colony Forming Unit (CFU): Viable micro-organisms (bacteria, yeast & mold) capable of growth under the prescribed conditions (medium, atmosphere, time and temperature) develop into visible colonies (colony forming units) which are counted. The term colony forming unit (CFU) is used because a colony may result from a single micro-organism or from a clump /cluster of micro-organisms. It is normally expressed as CFU per g or ml.

Colony Counter: A colony counter is an instrument used to count colonies of bacteria or other microorganisms growing on an agar plate or media plate.

Petri Dish: A Petri dish (or Petri plate or cell culture dish) is a shallow glass or plastic cylindrical lidded dish that biologists use to culture cells.

Agar Plate: An agar plate is a Petri dish that contains a growth medium (typically agar plus nutrients) used to culture microorganisms.


Materials & Equipment’s

  • Media to be tested (TSB,FTM,TSA)
  • Following type of Bacterial Cultures
  • Bacillus Subtilis ATCC # 6633
  • E. Coli ATCC # 8739 Bacterial Source
  • Pseudomonas aeruginosa ATCC # 9027
  • Staphylococcus aureus ATCC # 6538
  • Candida albicans ATCC # 10231 Mold Source
  • Clostridium sporogenes ATCC # 19404
  • Sterilized Petri Plates /Flasks
  • Bacterial Wire Culture Loops
  • Hot incubator & cool incubator
  • Autoclave
  • Colony counter
  • Petri plates/flasks
  1. Prepare the media as per Standard Operating Procedure (SOP) for Growth Promotion Test and pre-incubate as per SOP of Pre incubation of media’s.
  2. Transfer the bacterial cultures, media’s and streaking loops inside the sub culturing room under Biosafety cabinet.
  3. Perform the test under BSC by adopting all necessary gowning.
  4. Label the plate / flask with type of media into it.
  5. If media under test is for anaerobic bacterial detection / presence checking, as Fluid Thioglycollate Media (FTM), subculture it with bacterial source strains as mentioned above.
  6. If media under test is for mold or fungi detection / presence checking, as Soya Bean Casein Digest Medium (SCDM), subculture it with mold source strains as mentioned above.
  7. If media under test is made for bacterial and mold detection / presence checking, as Soya Bean Casein Digest Medium / Tryptic Soya Agar or TSB, subculture it with both bacterial source strains as well mold source strains separately.
  8. Red heat the bacterial wire loop on flame, cool it by touching the agar media into Petri plates
  9. Pick the culture with sterilized loop and transfer it into the respective media aseptically as described below in table1.
  10. In case of agar media, streak the culture with the help of wire loop.
  11. Label the flasks / plates with their respective inoculated cultures.
  12. Incubate the test sample flasks / plates at their respective optimum growth temperatures as for bacteria 30 – 35 °C for 48 – 72hrs and for mold 20 – 25 °C for 5days.
  13. Check the Medias for growth on daily basis, If Medias show proper growth, use them for routine lab testing, otherwise reject the media.
  14. Record the results
  15. Discard the Medias containing growth as per SOP of Disposal of Contaminated Cultures.

Table 1

Name of Media Positive culture to be used for Growth Promotion Test Expected growth characteristics of the test organism for the respective media Incubation Temperature Incubation Period
Fluid Thioglycollate Medium B. subtilis,P. aeruginosa S. aureus -Growth (Turbidity) Observed in the     respective media    tubes 30 to 35 °C 2-3days
Soybean Casein Digest Medium B. subtilis C. albicans A. Niger C. sporogenesis -Growth (Turbidity) Observed in the respective media tubes 20 to 25 °C 5days
Soybean Casein digest Agar E.coli  P. aeruginosaS. aureus -Opaque white  colonies on SCDA Plates-Large grayish colonies on SCDA Plates-Tiny white colonies on SCDA Plates 30 to 35 °C 2-3days


  1. Document the results of the Standard Operating Procedure (SOP) for Growth Promotion Test in a report format, including observations, interpretations, and any corrective actions taken.
  2. Retain the records for a specified period as per the laboratory’s quality management system requirements.

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