The standard "ASTM E2180-18 Standard Test for Determining Activity of Antimicrobial Agents Incorporated in Polymeric or Hydrophobic Materials" published by the American Society for Testing and Materials (ASTM) describes a test method used primarily for the purpose of evaluating (quantitatively) the antimicrobial activity of agents incorporated or bound to flat (two-dimensional) hydrophobic or polymeric surfaces. This method focuses primarily on evaluating antibacterial activity, but other microorganisms such as yeast and fungal conidia can also be tested using this method.
The inoculation vehicle is an agar slurry that reduces the surface tension of the saline inoculation carrier and allows for the formation of a mock biofilm that allows for more even contact of the inocula with the test surface. This test method facilitates the testing of hydrophobic surfaces using cells held in an agar slurry matrix. However, this test method is not suitable for determining activity against biofilm cells that are both genetically and metabolically distinct from the planktonic cells used in this test.
The test method described can confirm the presence of antimicrobial activity in plastics or hydrophobic surfaces and allows the determination of quantitative differences in antimicrobial activity between untreated plastics or polymers and those containing bound or incorporated low water-soluble antimicrobial agents. Comparisons can also be made between the numbers of survivors on preservative-treated and control hydrophobic surfaces.
This method also allows determination of the shelf life or long-term stability of an antimicrobial treatment, which can be achieved by testing both unwashed and washed samples over a period of time. However, knowledge of microbiological techniques is required to apply these test methods.
Briefly, this test method can be used to evaluate the effectiveness of antimicrobials incorporated or bound in hydrophobic materials such as plastics, epoxy resins, and other hard surfaces. The water-based bacterial inoculum remains in close, uniform contact with the treated material as a pseudo-biofilm. The percent reduction in populations of surviving fastidious bacterial cells at 24 hours is determined compared to those obtained from an untreated control. The hydrophobic substrate can be tested repeatedly over time to assess sustained antimicrobial activity.
For the purposes of this standard, the following terms and definitions apply:
This method involves inoculating a molten (45°) agar slurry with a standardized bacterial cell culture. A thin layer (0,5–1,0 mL) of the inoculated agar slurry is pipetted onto the test and untreated control material (a minimum of three samples are used). After the specified contact time (usually 24 h), surviving microorganisms are recovered by elution of the agar slurry inoculum from the test substrate into the neutralizing broth and extracted by methods that ensure complete removal of the inoculum from the test material (e.g. sonication, vortexing or manual extraction, i.e. stomacher).
Serial dilutions are made, followed by pour or spread plates from each dilution. Agar plates and dilution broths are incubated for 48–62 hours at a specified temperature, depending on the optimum temperature for the test organism. Bacterial colonies from each dilution series are counted and recorded. Percent bacterial reduction in treated and untreated samples is calculated.
This method can be used to evaluate the effectiveness of conjugated/bound antimicrobials on hydrophobic materials such as plastics, epoxy resins, and other hard surfaces. The water-based bacterial inoculum remains in close, uniform contact with the treated material as a pseudo-biofilm. The percent reduction in surviving populations of challenged bacterial cells at 24 hours is determined compared to those from an untreated control. The hydrophobic substrate can be tested repeatedly over time to assess persistent antimicrobial activity.
Our organization, which has been trying to support businesses from every sector with its testing, measurement, analysis and evaluation studies carried out in a wide range for years, has a strong staff that closely follows the developments in the world in the field of science and technology and constantly improves itself. In this context, testing services are also provided to businesses in accordance with the "ASTM E2180-18 Standard test to determine the activity of antimicrobial substances included in polymeric or hydrophobic materials" standard.
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