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SOP for Quantification of Microbial Culture

Standard operating procedure of qualification of microbiological cultures used as reference in microbial analysis.


       To describe a procedure for quantification of culture

2.0  SCOPE

       This SOP is applicable for quantification of culture


       Microbiologist - Quality Control


       Manager- Quality Control


5.1  To perform the experiments select 24 hours old bacterial culture, yeast culture and sporulated culture of fungi.
5.2  The cultures are to be selected i.e. environment isolates. Bacillus subtilis, Staphylococcus aureus, Salmonella sp, pseudomonas aeruginosa. E.coli, Candida albicans, Aspergillus niger.
5.3  Preparation of culture media
5.3.1  Prepare the culture media as per the SOP of media preparation and qualify the medium for fertility test.
5.4  Quantification of culture
5.4.1  Take the bacterial culture 24 hours old slant, harvest the slant in peptone water aseptically in pre-sterilized 9 ml peptone water tube.

5.4.2  Dilute the harvested culture in pre-sterilized 9 ml peptone water containing test tube using sterile micropipette tips. 
5.4.3  Quantification of fungal culture, use sterile saline and sterile glass beads for harvesting 
5.4.4  Do the serial dilution of culture up to 10-1, 10-2, 10-3, 10-4, 10-5, 10-6, 10-7, 10-8, 10-9, 10-10 dilution.
5.4.5  Do the pour plating of 1 ml culture suspension from all dilution in duplicate add SCDA medium for bacteria, SDA for fungi (temperature of media should be 40°C- 45°C.
5.4.6  Incubate the bacterial culture 30°C- 35°C for 72 hours and fungal culture 20°C- 25°C for 5 day.
5.4.7  Record the result after incubation as per Annexure – I
5.4.8  Select the dilution, which falls between 10 to 100 cfu /ml. Refrigerate all dilution at 2°-8°C.

Related: Maintenance of Microbial Cultures


6.1  SOP - Standard Operating Procedure 
6.2  SCDA - Soyabean Casein Digest Agar 
6.3  Cfu - Colony Formation Unit 
6.4  SDA - Saboraud’s Dextrose Agar 

CULTURE TITRATION RECORD (Culture Quantification)
Name of organisms
Date of sub culturing
B. No. of culture
Date of plating/ incubation
Incubation time & temp
Media lot No

Quantification Table
Count obtained
Name of organisms











Culture titre value

Dilution Vol. Suspension used

Date of completion

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Ankur Choudhary is India's first professional pharmaceutical blogger, author and founder of Pharmaceutical Guidelines, a widely-read pharmaceutical blog since 2008. Sign-up for the free email updates for your daily dose of pharmaceutical tips.
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