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SOP on Preparation and Preservation of Culture Suspension

  • Objective

To lay down the procedure for Preparation and Preservation of 10-100 CFU’s/0.l ml Culture Suspension.

  • Scope

This SOP is applicable for Preparation and Preservation of 10-100 CFU’s /0.1 ml Culture Suspension in Microbiology Laboratory of (Pharmaceutical Company Name).

  • Responsibility
    • Microbiologist or above of Microbiology Laboratory: Preparation of SOP.
    • Head – Microbiology section / Nominee: Checking of the SOP.
  • Accountability
    • Head – Quality Control / Nominee: Compliance of SOP.
  • Abbreviations and Definitions

QC                              :            Quality Control

SOP                             :            Standard Operating Procedure.

CFU                            :            Colony forming Units

  • Procedure
    • Perform all inoculations aseptically under LAF in sub-culturing room.
    • Prepare the media used for this procedure as per the directions given in ‘Preparation of Sterile Media SOP No.: QC-SP-335-R00.
    • Prepare culture suspension by inoculating a small loop of culture from a Working Culture tube in to a tube containing 10 ml of sterile buffer solution (for aerobic bacterial and Candida albicans cultures, sterile Buffered Sodium Chloride — Peptone Solution pH 7.0 or Phosphate Buffer Solution pH 7.2, for Clostridium sporogenes, add 5 ml mineral oil, and for Aspergillus niger culture, add 0.05% of polysorbate 80 to the Buffer used for Candida albicans). Shake to disperse the cells uniformly and dilute the culture suspension.
    • To determine the proper dilution containing 10-100 cfu 10.1 ml, make 10 fold (imI in

10 ml) serial dilutions with same buffer used above and perform plate counts (Pour plating) in duplicate by plating 0.1 ml of each dilution using appropriate agar medium (Soyabean Casein Digest Agar medium for Aerobic bacteria, Reinforced Clostridial Agar for Clostridium sporogenes and Sabouraud Dextrose Agar medium for fungi, PNY agar medium for Lactic acid bacteria) and preserve all the dilutions in the refrigerator at 2-8 °C.

  • Incubate the plates as per the incubation conditions mentioned in Table-i.
  • Identify the dilution which yield 10 to 100 cfu /0.1 ml in both plates and calculate the average.
  • Label this tube with the following details.


10 — 100 CFU’s / 0.1 ml culture suspension
Name of the culture
Reference No.
Expiry date
  • Reference number: Assign the reference number as per following procedure.
    • CS-VY-####
    • Where, CS — Indicates Culture Suspension which will be written 2 alphabets —CS’ YY — Indicates Last 2 digits of the calendar year

#### — indicates Serial number in 4 numerals

E.g. For the first culture suspension prepared in the calendar year 2016, the reference number will be as follows, CS/16/0001

  • Discard all other dilutions as per SOP (Decontamination and Disposal of Used Media).
  • Document the results in the record, ‘Record for 10-100 CFU’s /0.1 ml culture suspension
  • Use this culture suspensions whenever required (e.g. for Growth promotion tests).
  • Allow the culture suspension tube to the room temperature before every use.

 Table-I. Culture Conditions for Microbial recovery

Name of the Organism Incubation Expiry Date
Time Temperature
Aspergilus niger 5-7 days


22.5 ± 2.5 °C






7 days from


the day of




of inoculum



Candida albicans 2-3 days


22.5 ± 2.5 °C


Salmonella abony 24-48 hours


32.5 ± 2.5 °C


Pseudomonas aeruginosa 24-48 hours


32.5 ± 2.5 UC


Escherichia coil 24-48 hours


32.5 ± 2.5 °C


Staphylococcus aureus 24-48 hours


32.5 ± 2.5 °C


Bacillus subtilis 24-48 hours


32.5 ± 2.5 °C


**Ciostridium sporogenes 24-48 hours


32.5 ± 2.5 °C


Lactic acid bacteria 24-48 hours


32.5 ± 2.5 °C



**lncubate the plates under anaerobic condition using anaerobic jar.

 Forms and Records (Annexures)

    • Record for 10-100 CFU’s/0.l ml culture suspension
  • Distribution
    • Master copy       –       Quality Assurance
    • Controlled copies   –       Quality Assurance, Production, Quality Control, Stores, Engineering and Human Resource
  • History:
Date Revision Number
Reason for Revision
00   NEW SOP



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About Pharmaceutical Guidanace

Mr. Shiv Kumar is the Author and founder of pharmaceutical guidance, he is a pharmaceutical Professional from India having more than 14 years of rich experience in pharmaceutical field. During his career, he work in quality assurance department with multinational company’s i.e Zydus Cadila Ltd, Unichem Laboratories Ltd, Indoco remedies Ltd, Panacea Biotec Ltd, Nectar life Science Ltd. During his experience, he face may regulatory Audit i.e. USFDA, MHRA, ANVISA, MCC, TGA, EU –GMP, WHO –Geneva, ISO 9001-2008 and many ROW Regularities Audit i.e.Uganda,Kenya, Tanzania, Zimbabwe. He is currently leading a regulatory pharmaceutical company as a head Quality. You can join him by Email, Facebook, Google+, Twitter and YouTube

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