Antimicrobial Testing (Dynamic)
For each product to be tested according to ASTM E2149-13a, three sterile containers are needed; one containing only the bacterial suspension, one containing the treated article in the bacterial suspension and another flask containing an untreated article, or control, also in the bacterial suspension.
All three containers are then placed onto a platform shaker at room temperature for a contact period of 1 hour, after which suspensions are cultivated onto agar in triplicate and the colony forming units (CFUs) are counted.
The results allow us to quantitatively determine the efficacy of the antimicrobial agent by analysing if the reduction of bacteria is significant compared to either the bacterial suspension recovery 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.
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 modifications from the standard 1-hour contact time to 24 hours, or other time periods as required.
Credibility of results
ASTM E2149-13a is a 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.