ASTM E2149 Determination of Antimicrobial Activity of Antimicrobial Agents Under Dynamic Contact Conditions

The standard “ASTM E2149 Standard Test Method for Determining Antimicrobial Activity of Antimicrobial Agents under Dynamic Contact Conditions” developed by the American Society for Testing and Materials (ASTM) describes a test method for evaluating the antimicrobial activity of antimicrobial-treated samples under dynamic contact conditions.

This dynamic shake flask test was developed for routine quality control and screening testing to overcome challenges in using conventional antimicrobial testing methods to evaluate substrate-bound antimicrobials. These challenges include ensuring inoculum contact with the treated surface (as in the AATCC TM100 standard), flexibility in recovering at different contact times, use of inappropriately applied static conditions (as in the AATCC TM147 standard), sensitivity, and reproducibility.

This test method provides the ability to evaluate many different types of treated substrates and a wide variety of microorganisms. The treated substrates used in this test method can be subjected to a wide variety of physical and chemical stresses or manipulations, allowing the versatility to test the effects of contamination from things like hard water, proteins, blood, serum, various chemicals, and other contaminants.

Surface antimicrobial activity is determined by comparing results from the test sample with controls run simultaneously.

This test method may not be suitable for all antimicrobial-treated materials or antimicrobial agents. The appropriate test methodology should be determined based on the antimicrobial's mode of action and end-use expectations. Appropriate neutralization of all antimicrobials should be verified using ASTM E1054 standard test methods.

This test method should only be performed by persons trained in microbiological techniques.

Substrate-bound antimicrobial agents generally do not diffuse freely into their environment under normal use conditions. This test method ensures good contact between the bacteria and the treated fiber, fabric, or other substrate by continuously agitating the test specimen in a challenge suspension throughout the test period.

The metabolic state of the challenge strain can directly influence measurements of the effectiveness of specific antimicrobial agents or agent concentrations. A strain's susceptibility to specific biocides can vary depending on its life stage (cycle). A one-hour contact time in a buffer solution allows for metabolic stasis in the population. This test method standardizes both the growth conditions of the challenge strain and the substrate contact times to reduce variability associated with the microorganism's growth stage.

Leaching of an antimicrobial depends on the test conditions used and the ultimate end use of the product. Additional testing may be required to determine whether a compound is bound to the substrate under all conditions or during product end use.

This test method cannot determine whether a compound has leached into solution or been immobilized on a substrate. This test method is designed only to determine activity as described in subsequent sections of the method. The test is suitable for evaluating stressed or modified samples when accompanied by adequate controls.

Stresses may include laundry, wear and tear, radiation and steam sterilization, UV exposure, solvent manipulation, temperature sensitivity, or similar physical or chemical manipulation.

ASTM E2149 is designed to evaluate the antimicrobial activity of materials treated with or containing antimicrobial agents. This standard is specifically designed for non-leaching or surface-bound antimicrobial materials and evaluates their ability to inhibit the growth of microorganisms in a dynamic environment.

The primary purpose of this standard is to determine how effective an antimicrobial-treated surface is at inhibiting or killing bacteria when subjected to constant motion or agitation. This is crucial because real-world applications such as medical devices, textiles, plastics, or food contact surfaces often experience dynamic conditions. Unlike other static methods (e.g., ASTM E2180 or AATCC 100), ASTM E2149 better simulates real-world use by ensuring that the entire surface of the sample is uniformly exposed to the test organisms under constant agitation.

In general, the testing procedure is as follows:

• Preparation of bacterial suspension: A known concentration of bacteria (usually E. coli or Staphylococcus aureus) is prepared in a nutrient-free saline solution to prevent cell growth during testing.
• Sample immersion: The antimicrobial-treated sample (e.g., plastic film, coated fabric) is placed in bacterial suspension.
• Dynamic incubation: The mixture is placed on a shaker (usually at 37 degrees) and shaken for 1 hour.
• Post-incubation sampling: After the incubation period, a sample of the solution is taken and plated to determine the number of viable bacteria (colony forming units or CFUs).
• Result calculation: To measure antimicrobial activity, the percentage reduction in bacterial counts compared to an untreated control is calculated.

The ASTM E2149 standard is widely used in the textile, plastics, coatings, medical and consumer goods industries to verify the effectiveness of:

• Antimicrobial coatings
• Hospital bedding and uniforms
• Food processing surfaces
• Water filtration materials
• Antibacterial polymers or resins

The ASTM E2149 standard is considered important for the following reasons:

• Dynamic testing: Unlike static methods, it better simulates real-world usage conditions where movement and contact occur.
• Evaluation of non-leaching materials: Ideal for testing antimicrobial surfaces where the active ingredient does not leach into the environment.
• Regulatory basis and marketing support: Demonstrates product performance for regulatory filings or consumer safety claims.
• Comparative analysis: Provides standardized measurements to compare antimicrobial performance across different materials or formulations.

As a result, ASTM E2149 is an important test method for evaluating antimicrobial surfaces under real-world, dynamic conditions. It provides manufacturers, researchers, and regulators with a consistent way to evaluate and compare the performance of antimicrobial agents in sealants. As demand for hygienic and antimicrobial products continues to grow across various industries, ASTM E2149 plays a crucial role in ensuring product effectiveness and consumer safety.

Our organization, which has been supporting businesses across all sectors for years with a wide range of testing, measurement, analysis, and evaluation activities, boasts a strong team of employees who closely follow global developments in science and technology and are constantly improving themselves. In this context, we also provide testing services in accordance with ASTM E2149 Standard Test Method for Determining the Antimicrobial Activity of Antimicrobial Agents Under Dynamic Contact Conditions.