USP 51 Antimicrobial Effectiveness Testing

TEST METHOD

USP <51> USP <51>

Antimicrobial Effectiveness Testing

USP <51> Antimicrobial Effectiveness Testing is a United States Pharmacopeia standard used to evaluate the effectiveness of antimicrobial preservatives in pharmaceutical and cosmetic products. The test measures microbial reduction over time against specified bacteria, yeast, and mold, with results reported as log reduction at defined intervals.

The diagram below summarizes the USP <51> test method.

TESTING CRITERIA AND CUSTOMER PROCESS

Step 1: What microorganisms are used?

USP <51> uses standard challenge microorganisms representing common contamination risks:

Bacteria: Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa.
Yeast and mold: Candida albicans and Aspergillus brasiliensis

Step 2: How is the test performed?

The product is inoculated with standardized microorganisms and incubated under controlled conditions. Samples are taken at defined time points to monitor microbial survival.

Step 3: How are results evaluated?

Microbial counts are measured at each time point and compared to the initial inoculum. Results are expressed as log₁₀ reduction to determine preservative effectiveness.

Step 4: What determines product compliance?

A product complies when it meets the required microbial reduction criteria for its applicable USP <51> category.

Step 5: Place an order and send your sample to us

Fill in the test request form and place an order via email at info@tecolab-global.com. We will advise on the quantity of sample required for testing.

You can deliver the sample to us via courier or our sample delivery service and provide us the tracking code. We will monitor the delivery status and inform you when we receive the sample.

Step 6: Track the status of your request

Once we have received your sample, we will provide a tracking number to you. You can easily track the status of your request here.

Step 7: Download your password-protected test report

Download your readily available test report online with just a single click using the link and password provided via email notification. We will receive a notification once you have downloaded the test report.

For safety purposes, the uploaded test report will self-destruct after 7 days.