Test Method ASTM E2149-13a Explained

Continuing with our blog series of explaining the different testing methods we employ here at BioLabTests to carry out microbiological testing for our clients, today we focus on ASTM E2149-13a.

What is the purpose of ASTM E2149-13a?

ASTM E2149-13a is a test method for determining the antimicrobial activity of antimicrobial agents under dynamic contact conditions. It is a sensitive shake flask test recommended for testing materials such as fabric, paper, powder and granular material. It evaluates the activity of an antimicrobial additive within non-leaching materials when shaken within an inoculated suspension. The number of viable organisms from the suspension is determined and the percentage reduction is calculated by comparing retrievals from appropriate controls.

How does the testing work?

For each product to be tested during ASTM E2149-13a, three sterile containers are needed; one containing the “inoculum only”, one containing the treated article and another flask containing an untreated article, or “control”.

Running simultaneously, all three containers are placed on a platform shaker at room temperature for a contact period of 1 hour, after which suspensions are cultivated onto agar in triplicate and the colonies forming units (CFUs) are counted.

The results allow us to quantitatively determine the efficacy of the antimicrobial agent on the treated surface by evaluating, if the reduction of bacteria is significant compared to either the inoculum or the untreated control. If any leaching of the antimicrobial additive is observed, results are deemed unreliable and the antimicrobial needs to be neutralised upon retesting the product.

What bacteria can be tested?

For the ASTM E2149-13A method, Escherichia coli ATCC 25922 is specified as the standard organism. Nevertheless, additional organisms can be requested, as well as an increase from the 1 hour contact time to 24 hours, or other time periods as required.

How credible are the results?

ASTM E2149-13a is a fairly reproducible method that also allows experimental flexibility to test products of several shapes and sizes, generally consisting of treated fabrics. Routine quality controls on media are also carried out to maintain efficacy and accuracy of results.