SOP for checking Efficacy of Disinfectant

The SOP is created for checking the efficacy of Disinfectant in the Microbiology of pharmaceuticals    

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To lay down a procedure for checking the efficacy of disinfectant.


This SOP of checking Efficacy of Disinfectant is applicable to all the disinfectants used in pharmaceutical organizations.




Quality Control Manager


Preparation of Inoculum:

Inoculate the microbial culture suspension in nutrient broth or soybean casein digest medium and incubate at 32°C±2.5oC for 24 hours.

After 24 hours again inoculate the same microbial culture suspension by transferring loop full of the previous suspension on soybean casein digest agar for 48hrs to refresh the microbial culture.

Prepare the suspension in sterile normal saline to achieve 105/ml.

Serially dilute the freshly reconstituted microbial culture to get 25-250 CFU/ per plate.

Keep freshly reconstituted culture at a temperature of 2o-8oC in refrigerator for future use.

Preparation of Disinfectant Dilutions in Different Concentrations: 

Prepare the serial dilutions of disinfectant from 0.5%-5%. 

Carefully add 1ml of the microbial culture suspension with 25-250CFU count to each serial dilution of the disinfectant solution and shake properly.

Set the dilutions containing microbial suspension with disinfectant for 10 minutes.

After 10mints take 1ml of solution from each serial dilution tube and transfer to tubes containing 20-25ml of a sterile nutrient agar with neutralizer and mix properly.

Let the plate solidify and incubate at 32°C ± 2.5°C for 48-72 hrs. 

Count the number of viable microbes/plate after the completion of incubation period and record the results.

The inactivators or neutralizer such as sodium thiosulphate (5% w/v solution), lecithin (0.5%) with tween-20 (4%) must be used for inactivation purpose depending on type of disinfectant used 

Acceptance Criteria

Recovery of microbial culture should be NMT10%.

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