JIS Z 2801 Test for Antimicrobial Activity of Plastics
The JIS Z 2801 method tests the ability of plastics and other antimicrobial surfaces to inhibit the growth of microorganisms or kill them. The procedure is very sensitive to antimicrobial activity. It involves inoculating the antimicrobial surface with a moderate, standardized microbial population, then covering it with a plastic film to prevent evaporation over the course of the contact time, which is usually 24 hours. After the contact time, percent reductions are calculated.
The JIS Z 2801 procedure has been adopted as an International Organization for Standardization (ISO) procedure, ISO 22196.
Summary of the JIS Z 2801 Test
- The test microorganism is prepared, usually by growth in a liquid culture medium.
- The suspension of test microorganism is standardized by dilution in a nutritive broth (this affords microorganisms the potential to grow during the test).
- Control and test surfaces are inoculated with microorganisms, in triplicate, and then the microbial inoculum is covered with a thin, sterile film. Covering the inoculum spreads it, prevents it from evaporating, and ensures close contact with the antimicrobial surface.
- Microbial concentrations are determined at "time zero" by elution followed by dilution and plating.
- A control is run to verify that the neutralization/elution method effectively neutralizes the antimicrobial agent in the antimicrobial surface being tested.
- Inoculated, covered control and antimicrobial test surfaces are allowed to incubate undisturbed in a humid environment for 24 hours.
- After incubation, microbial concentrations on are determined. Reduction of microorganisms relative to initial concentrations and the control surface is calculated.
Strengths of the JIS Z 2801 Test
- The method is quantitative and results tend to be reproducible, provided the inoculum does not spill off of the target area after being covered with the thin film.
- The method tests for both bacteriostatic (growth-inhibiting) and bactericidal (bacteria-killing) properties.
- Microbial concentrations are standardized, and bacteria are provided with nutrients during the incubation period, which provides them with ample opportunity to grow if surfaces aren't sufficiently antimicrobial. This is in contrast to certain other antimicrobial tests, where microbes are "incubated" in non-nutritive suspensions, which itself may be stressful over long periods.
- The method stipulates triplicate experimentation, which helps researchers estimate the precision of the individual tests and increases overall experimental accuracy.
- The method includes a "pass/fail" criterion for the calculated levels of antimicrobial activity observed in test samples, making determinations of antimicrobial activity less discretionary.
Weaknesses of the JIS Z 2801 Test
- The JIS Z 2801 method is not necessarily representative of actual surface contamination events, since a relatively dilute liquid microbial inoculum is spread over a considerable surface area, and then is kept wet (usually for a period of 24 hours). Most of the time, microbial contaminants dry quickly onto surfaces. This limits the time that an aqueous medium is available to facilitate interaction between the antimicrobial surface and microorganisms. This means that JIS Z 2801 is a "best-case" sort of test for many products.
- It is not uncommon for "control" plastics to exert low-level antimicrobial activity, so identification of an ideal control surface may be challenging.
Though the JIS Z 2801 test is somewhat "best-case," it is an excellent way to quantify the antimicrobial activity level of an antimicrobial surface, especially one that is hydrophobic. Among the various tests for antimicrobial activity of surfaces, this has emerged as one of the industry standards. For more information about the JIS Z 2801 test for antimicrobial surfaces, Contact the Lab Today!