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SOP for Neutralization of Inhibitory Substances

To lay down a procedure for the neutralization of inhibitory substances.

This SOP is applicable to the neutralization of inhibitory substances present in the test preparation for microbiological analysis at PharmaSky Limited.

Microbiologist – Responsible for doing activities.
QC Head – Responsible for implementing the procedure.
QA Head – Overall Compliance.

  • Before doing regular microbial analysis, validation is to be conducted to demonstrate the absence of an inhibitory substance that may affect the growth of the microorganisms present in the article under test conditions.
  • This can be done by adding 1 mL of not less than 10-3 dilutions of a 24-hour broth culture of the following microorganisms to the first dilution (in pH 7.2 phosphate buffer, fluid soya bean casein digest medium, or fluid lactose medium) of the test material and follow the common test procedure as per the current version of General Test Procedure.
  • Test cultures:
  1. Escherichia coli
  2. Staphylococcus aureus
  3. Pseudomonas aeruginosa
  4. Salmonella
  • If the organism fails to grow, the test preparation is modified by the following options
  1. By increasing the volume of the diluent, the quantity of test material remains the same.
  2. By adding suitable inactivating agents (4.0 % Polysorbate 20 or 0.05 % Polysorbate 80 & 0.5% Soya lecithin).
  3. By combining both.
  • If it is not possible to recover the inoculated viable culture, alternatively go for the membrane filtration method.
  • In the case of an article that is not suitable for applying membrane filtration, continue the plate count method to establish the spectrum of inhibition and bactericidal activity of the article.
  • This may indicate that the article is not likely to be contaminated with the given species of microorganisms due to the bactericidal activity of the product.

QC: Quality Control
QA: Quality Assurance
SOP: Standard Operating Procedure
%: Percentage



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