USP <51> Antimicrobial Efficacy

Antimicrobial Efficacy Testing

The objective is to assess the effectiveness of inherent or added antimicrobial preservatives in a product.  The sample is spiked with a known amount of microbial load and depending on product type is analyzed on day 7, 14 and 28.

Method Suitability

An initial method suitability is performed to demonstrate at least a 70% recovery of spiked organisms.  Method suitability includes determination of an appropriate dilution factor and which inactivators are required for the particular product under test. Method suitability is performed concurrently with the AET test and is generally completed by day 5.  The information obtained from method suitability is applied to sample analysis on days 7, 14 and 28.

Sample Quantity Required

A 75 mL quantity for a liquid or 75 g of a cream is recommended and is sufficient for both method suitability and AET testing. 

Turn Around Time

The test itself requires a minimum of 33 days from initiation and reports are generally issued within 40 days from sample receipt.