- To interface this SOP to the actual practices of flow patterns.
- To ensure that the SOP is updated & reflects the actual execution.
- To review the SOP in case of any change or whenever it is due for revision.
- To follow the instructions laid down by this SOP.
- To keep the relevant SOPs valid and updated.
- Before preparation check the expiry date and label the bottle with name and date of preparation.
- Complete instructions for the preparation of culture media are given on the label of each bottle, according to it,
- Open the culture medium bottle away from direct air flow and moisture. Weigh the desired quantity of required medium quickly, accurately and without creating 'clouds of dust'.
- Reclose the medium bottle as soon as possible.
- Always use freshly prepared purified water.
- Pour half of the required volume of purified water in a clean bottle which is twice the final volume of the medium to allow adequate mixing.
- Then transfer the weighed quantity of medium slowly along with agitation as the medium can not accumulate to make a clump.
- Pour the rest of the purified water down the sides of the vessel to wash any adherent medium back into the solution. This is an important step because dry culture media powder above the level of the water may not be sterilized in the autoclave and may be a source of contamination.
- Sterilize using a validated process of autoclave, then check its pH value, if the adjustment is required then adjust it by using NaOH/HCl.
- After sterilization, pre-incubate the sterilized medium at 20 – 25°C for 3 – 5 days, if the medium shows any sign of turbidity then DO NOT it for testing purpose.
- Broth medium is kept in the same medium bottle whereas agar medium is poured in pre-sterilized Petri dishes when the medium temperature drops at 45 – 50°C.
- Mix the medium gently by rotating the flask or bottle. Avoid forming air bubbles. Dispense aseptically about 15 – 20 mL medium into Petri dishes (90 – 100 mm diameter) under the laminar airflow cabinet.
- Agar plates should be of an even depth and of a firm gel.
- When the medium has gelled and cooled, stack the plates and preincubate them for 3 – 5 days, if plates show any sign of colony then DO NOT use it for testing purpose.
- Record the medium preparation activity in its specified log book.
Media |
Required % & pH |
* Required Quantity
per 100 mL |
** Sterilization °C,
Time & Pressure |
Tryptic Soy Agar |
4.0%, 7.3 |
4 g |
121°C, 15 minutes, 15 psi |
Tryptic Soy Broth |
3.0%, 7.3 |
3 g |
121°C, 15 minutes, 15 psi |
Sabouraud Dextrose Agar |
6.5%, 5.6 |
6.5 g |
121°C, 15 minutes, 15 psi |
Sabouraud Dextrose Broth |
3.0%, 5.6 |
3 g |
121°C, 15 minutes, 15 psi |
Enterobacteria Enrichment Mossel Broth |
4.5%, 7.2 |
4.5 g |
121°C, 5 minutes, 15 psi |
Mannitol Salt Agar |
10.8%, 7.4 |
10.8 g |
121°C, 15 minutes, 15 psi |
Cetrimide Agar Selective &
Pseudomonas Cetrimide agar |
4.53%, 7.2 |
4.53 g |
121°C, 15 minutes, 15 psi |
Reinforced Medium for Clostridia |
3.8%, 6.8 |
3.8 g |
121°C, 15 minutes, 15 psi |
MacConkey’s Broth |
3.5%, 7.3 |
3.5 g |
121°C, 15 minutes, 15 psi |
MacConkey’s Agar |
5.0%, 7.1 |
5 g |
121°C, 15 minutes, 15 psi |
Rappaport Vassiliadis Salmonella
Enrichment Broth |
4.18%, 5.2 |
4.18 g |
115°C, 15 minutes, 15 psi |
Violet Red Bile Glucose Agar |
3.95%, 7.4 |
3.95 g |
Heat in Water bath, boil for 2 minutes, don’t
autoclave |
Xylose Lysine Deoxycholate Agar |
4.0%, 7.1 |
4 g |
Don’t autoclave, sterile on boiling |
Columbia Agar |
4.2%, 7.3 |
4.2 g |
121°C, 15 minutes, 15 psi |
Buffered Peptone Water |
2.55%, 7.0 |
2.55 g |
121°C, 15 minutes, 15 psi |
Antibiotic medium 11 |
3.05%, 8.3 |
3.05 g |
121°C, 15 minutes, 15 psi |
- During weighing, care must be taken and weigh accurately according to the manufacturer’s specifications.
- Before weighing, properly label the bottles with name, percentage and date.
- Weigh the desired quantity of required medium quickly, accurately and without creating 'clouds of dust'.
- After weighing, reclose the bottle as soon as possible because the dehydrated medium is hygroscopic.
- Always wear a mask and gloves for avoiding inhalation and skin contact.
- After sterilization, Do Not make heavy agitation for mixing as air bubbles do not form, mix in a gentle clockwise motion, especially in agar medium.
- If shrinkage OR dryness of agar surface is found, then it should be discarded without its usage for test.
- Contaminated medium either broth OR agar medium should be disposed-off according to SOP.
- Do Not use agar plates that contain heavy moisture.
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