Testing Solutions >> Non-Sterile Products Testing >> Preservative Efficacy Test / Antimicrobial Effectiveness Test

Preservative Efficacy Test (PET) or Antimicrobial Effectiveness Test (AET)

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Antimicrobial Effectiveness testingAntimicrobial Effectiveness Testing


Antimicrobial preservatives are substances added to products to protect them from microbiological growth or from microorganisms that are introduced inadvertently during or subsequent to the manufacturing process. In the case of products packaged in multiple-dose containers, antimicrobial preservatives are added to inhibit the growth of microorganisms that may be introduced from repeatedly withdrawing individual use doses. 

Products such as multi-dose pharmaceutical medicines, cosmetic products, personal care products will normally contain preservatives and needs to be tested. Therapeutic Goods Administration (TGA) also has guidance document on their website on Microbial quality of prescription and over-the-counter medicines. Click here to access it.

Preservative efficacy testing (PET) or antimicrobial effectiveness testing (AET) is required for the assessment of the antimicrobial preservation of multiple-use cosmetic and pharmaceutical products.

In Eurofins | ams, our clients (Australian or International) may choose the challenge test to be conducted in accordance with the British Pharmacopoeia (BP), US Pharmacopoeia (USP), a combination of both, a client specific protocol or another nominated method.


Antimicrobial preservatives are added to products to prevent or limit microbial contamination, which can occur during normal conditions of storage and use.  The efficacy of an antimicrobial preservative may be enhanced or diminished by the active constituent of the preparation, or by the formulation in which it is incorporated, or by the container and/or closure being used as the final packaging material.

The test method must be qualified for the product under evaluation to ensure the correct diluent is used in assays for surviving microorganisms.

The product is inoculated with specified number of each challenge organism.  The inoculated product is held at room temperature for 28 days.  It is examined by the duplicate plate count method to determine the number of viable microorganisms which survive at each specified time interval.

All results are evaluated in accordance with the tabulated acceptance criteria of the relevant Pharmacopoeia’s or test protocols.

To read up more about Preservative Efficacy Testing (PET), do visit our Resource Centre to view past presentations or webinars on this topic. 


  1. Current BRITISH PHARMACOPOEIA (BP), Appendix XVIC, Efficacy of Antimicrobial Preservation.
  2. Current UNITED STATES PHARMACOPOEIA, General Tests and Assays USP <51>, Antimicrobial Effectiveness Testing.


Product Validation: 50g or 50ml

PET: 150 – 200 g or 150 - 200 ml


Test Protocols
Method Code Test Description Turnaround Time
TMPC-107 PET as per BP 5-6 weeks
TMPC-108 PET as per USP 5-6 weeks
TMPC-109 PET as per BP & USP 5-6 weeks