SOP For calibration of microbial culture inoculum used for microbiological testings is described in this post which you can follow in the section of microbiological lab. 

Objective:

This procedure has been established for calibration of microbial culture inoculum used for microbiological testing's.

Scope:

This procedure is applicable to microbiology lab.

Responsibility:

Microbiologist.                              

Accountability:

Quality Control Manager.             

Procedure:        

Prepare 1% aqueous barium chloride and 1% aqueous sulfuric acid solutions. 

Add the amounts to clean dry tubes as given below in table:


Tube No

1% Barium Chloride (ml)

1% Sulphuric Acid (ml)

Density Of Bacteria

(Million/ml)

1.    

0.1

9.9

300

2.    

0.2

9.8

600

3.    

0.3

9.7

900

4.    

0.4

9.6

1200

5.    

0.5

9.5

1500

6.    

0.6

9.4

1800

7.    

0.7

9.3

2100

8.    

0.8

9.2

2400

9.    

0.9

9.1

2700

10.     

1.0

9.0

3000

Prepare, with 0.1% peptone water a serial dilution of microbial culture with 05 pairs of test tube each pair contains different quantity of inoculum.

Check or observe the transmittance of barium sulfate standards on UV Spectrophotometer at a wavelength of  620nm and peptone water with concentration of 40.1% as blank solution.

Now compare the transmittance of each pair of the microbial inoculum having different dilution i.e. Inoculum of tube # 1 must corresponds to tube # 3 and same way the transmittance of tube #2 must corresponds tube #4   1200 (bacteria in million/ml). 

Now select randomly two tubes from remaining pairs and aseptically transfer the inoculum onto plate y pour plate method and after the completion of incubation period calculate cfu/ml with the help of colony counter.

The plate which shows  a viable count of 100 cfu/ml use it for inoculation in growth promotion tests and for validation of media.