ASTM E2315-16. Assessment of Antimicrobial Activity Using a Time-Kill Procedure.

Test accredited by ENAC (Spanish National Accreditation Entity).

The ASTM E2315 standard describes a method to evaluate the reduction of a population of aerobic microorganisms in contact with an antimicrobial test material after a certain interval or intervals of time. The test material must be a liquid or a solid that forms a uniform solution in water.

The test material, at the test concentration(s) requested by the customer, is contacted with a known population of microorganisms for a specified period(s) of time at a specified temperature. Test concentrations must be selected by the client, and each concentration will be tested in duplicate. Test intervals must be selected by the client, e.g. 15 seconds, 30 seconds and 60 seconds, or any range covering several minutes or hours. The test temperature indicated by standard is 25ºC, but the standard also establishes that additional temperatures can be used depending on the intended use of the product, for example, 22ºC for room temperature, 30ºC for temperature of human skin and 38ºC for temperature of warm water.

In accordance with ASTM E2315, the test organisms may be representative of the microbial flora encountered under the conditions of use of the test material or may be standardized strains. In our laboratory we offer the bactericidal activity determination test with reference strains of the following microorganisms: Pseudomonas aeruginosa, Staphylococcus aureus, Enterococcus hirae, Escherichia coli, Escherichia coli K12, Proteus hauseri, Salmonella typhimurium, Lactobacillus brevis and Enterobacter cloacae. To demonstrate activity against yeasts, the assay with Candida albicans, Saccharomyces cerevisiae and Saccharomyces cerevisiae can be requested; and if activity against filamentous fungi is required, the test can be performed with Aspergillus brasiliensis.

After the specified times, the samples are neutralized to quench the antimicrobial activity of the test material at specified sampling intervals and the number of surviving microorganisms is determined. The log reduction and percentage reduction for each concentration of test substance and at each of the selected time intervals are calculated, comparing the initial and final counts. The ASTM E2315 standard does not establish the requirements to consider a product as effective.