What is the purpose of the ISO 22196 test?
Simply put, ISO 22196 is a test method that quantitatively measures the antibacterial activity of plastics and other non-porous surfaces. This is an established standard method of testing the ability of treated surfaces to kill (bactericidal) or prevent growth (bacteriostatic) over 24 hours. This is a fairly sensitive assay that can detect low levels of antibacterial activity and obtain reproducible results based on Japanese Industrial Standards (JIS) Z 2801.
Antibacterial agents are substances that kill microorganisms such as bacteria, molds, and fungi. Antibacterial substances provide a higher level of product protection by inhibiting the growth of microorganisms on the surface for a very long period of time.
ISO 22196 was born as a quantitative method for assessing the antibacterial activity of plastics and other non-porous surfaces treated with antibacterial agents.
The ISO 22196 standard was designed by the International Organization for Standardization (ISO) based on the JIS Z 2801 standard issued by the Japanese Standards Association (JIS), and two test methods are supported.
Principle of method
The principle of this is based on the determination of viable bacteria after inoculation on the untreated reference and treated sample and after the appropriate contact time between the material and the bacterial inoculum. Therefore, this determination makes it possible to calculate the log-growth difference between the control and the treated sample, which makes it possible to estimate the antibacterial activity of the material.
Standard antibacterial activity has been tested against two strains representing Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus).
Solution / action
Typical antibacterial substance
• Copper (Cu) kills bacteria with high efficiency. However, antibacterial Cu film is not recommended for display products due to its yellowish color and low transparency.
• ZnO is an effective antibacterial agent found in sunscreens to protect the skin. ZnO is listed as “Generally Recognized as Safe” (GRAS)
• Ag has been used as an antibacterial agent to kill bacteria.
• TiO2 is widely used as a photo catalytic disinfectant for surface coatings. The FDA has approved it for use in human food, pharmaceuticals, cosmetics, and food packaging.
How to test antibacterial activity?
One of the most required, fast, and reliable antibacterial tests (hard surfaces such as plastic and glass) to determine antibacterial activity and antibacterial effect is JIS Z 2801.
JIS Z 2801 is a Japanese industry standard established in 2000 as “Antibacterial Products-Antibacterial Activity / Effectiveness Test.” After that, JIS Z 2801 was adopted as ISO 22196 (Plastic: Measurement of antibacterial activity on the plastic surface).
How does the test work?
iso 22196 jis z 2801 is performed three times by inoculating the control surface and the test surface with bacteria. The sample surface is then covered with a sterile coverslip to prevent evaporation. Then incubate for 24 hours in a humid environment. After incubation, the antibacterial effect is determined. It involves recovering the remaining bacteria by rinsing the surface with a liquid neutralizing medium. Bacteria in this liquid are listed below by growing in a nutrient-rich solid medium called agar. As it grows, it counts and becomes a colony-forming unit. This allows you to calculate the reduction of bacteria on the treated surface relative to the result of the control sample or the initial amount placed in the sample. These steps allow you to see if the surface tested is bacteriostatic, bactericidal, or beneficial to bacterial growth.
The ISO 22196 standard specifies two types of bacteria and that samples should be tested against Staphylococcus aureus and E. coli. However, these can be replaced according to customer needs and tested against more commercially relevant products and microorganisms such as MRSA, Pseudomonas aeruginosa, Campylobacter, Salmonella.
How reliable are the results?
Some argue that this method has some limitations and does not accurately represent pollution events. The treated surface may meet the requirements of ISO 22196, but “life” studies may not show the same results.
It is worth considering that ISO 22196 can be run under “real” laboratory conditions. However, this method provides the bacteria with ideal growth conditions, which would otherwise interfere with the material’s performance and allow control of conditions that could obscure it. In “real life,” you cannot control or know the number of bacteria that have grown and what they have been reduced to. Also, it is not possible to know if the control was treated the same as the test sample. As a result, ISO 22196 provides a viable alternative for assessing whether a product provides bacterial reduction.
A variety of environmental conditions can be changed according to customer needs, such as inoculum concentration, UV irradiation, and shortened contact time. This allows you to simulate various conditions, but the controlled lab test environment ensures reproducible results.
The current version of JIS Z 2801 is based on ISO 22196. These tests are technically the same method published by two different organizations
Bacterial Test-ISO22196-Plastic Bacterial Test
Inoculate the test organism into the sterile diluted nutrient broth. The broth is then distributed across the surface of the test tube. Antibacterial activity is measured by determining the number of viable cells recovered on the control material compared to the number of viable bacterial cells recovered on the specimen treated after 24-hour contact.
• This test method covers plastic, metal, and ceramic products.
• Not for textiles
• The test method shows Staphylococcus aureus ATCC # 6538P and E. coli ATCC # 8739 as test organisms, but other organisms can be used.
Also read — Know how AST is Indispensable in the Microbiology.
