Understanding ISO 22196: Antibacterial Testing for Plastics and Non-Porous Materials

Key takeaways

• ISO 22196 is an internationally recognized test for measuring the antibacterial activity of treated plastics and non-porous materials.
• The method compares treated samples with untreated surfaces after 24 hours of incubation to enumerate bacterial reduction.
• Results are expressed as R value (Log reduction). It determines the level of bacterial performance. 
• This standard is applicable only to smooth, non-porous, antibacterial-treated materials and does not include porous surfaces, antiviral or antifungal activity. 
• Manufacturers use ISO 22196 to validate antimicrobial claims, support regulatory documentation, and demonstrate product differentiation in global markets.

Summary 

ISO 22196 is an international test standard that is used to evaluate the antibacterial activity of plastics and other non-porous surfaces by measuring the reduction of specific bacteria after 24 hours of contact. This test method provides standardized proof of bacterial reduction, making claims defensible and comparable across markets.

Why does ISO 22196 testing matter?

Without  standardized testing, performance claims become invalid, hard to compare and risky from regulatory point of view. Buyers, regulatory bodies and B2B partners expect data generated in accordance with recognized international standards. 

ISO 22196 fills that gap by providing a structure. It provides a controlled method to evaluate bacterial reduction under specific test conditions such as temperature, humidity, inoculum load and contact time.  ISO 22196 testing helps help with –

• Establishing reproducible laboratory conditions
• Reducing regulatory risk
• Enabling standard performance comparison
• Supporting antimicrobial claims
• Providing validation data which is accepted globally. 

Here’s the thing. Marketing claims are easy. Quantified proof is not.

Survival of bacterial pathogens on inanimate objects threatens to increase direct transmission of infection, ultimately raising susceptibility to chronic hospitalization and mortality. In order to avoid microbial contamination, antibacterial treatments are incorporated to maintain a sterile environment on surfaces and other non- porous materials.

ISO 22196 standard specifies antibacterial surface test. This test method is used to evaluate the effectiveness of antibacterial treated plastics and other non – porous materials. 

How Does ISO 22196 Testing Work? 

• ISO 22196 test is performed by inoculating test bacteria on both treated and untreated samples.  
• Inoculated surfaces are covered with a sterile film and incubated for 24 hours or recommended time period in a humid environment.
• Post incubation period, test surfaces are transferred to a neutralising solution immediately. The solution inhibits bactericidal activity.
• After this, the neutralized extract is plated and incubated. It is used to determine remaining viable cells. 

Test Conditions for ISO 22196 testing

• Test organisms:  Staphylococcus aureus (ATCC 6538P), Escherichia coli (ATCC 8739)
• Sample size: Typically 50 mm × 50 mm plastic specimens (treated and untreated control)
• Incubation period: In ISO22196 testing for plastics, the incubation period is typically 24 hours. During this period, the bacterial inoculum on the plastic surface is incubated under controlled temperature and humidity. The 24-hour incubation period allows sufficient time for the bacteria to interact with the surface, enabling an accurate assessment of the antibacterial properties of the material by measuring the reduction in bacterial growth after this time.
• Temperature: The test specimens are incubated at 35°C ± 1°C (95°F ± 1.8°F). 
• Humidity: The relative humidity during the incubation period is maintained at ≥ 90%. 

Passing Criteria

Antibacterial activity is expressed as R value (log reduction). This is calculated based on the logarithmic difference between the bacterial count on the untreated surface and that on the treated surface.

Higher R value = stronger antibacterial effect

Precautions to be considered while performing the test

Conducting ISO 22196 tests requires careful adherence to procedures to ensure accurate and reliable results. The following precautions should be taken during the testing process:

• Sterilization of equipment: All equipment and materials used for testing should be previously sterilized in order to avoid any contamination which may alter the results.
• Control of environmental conditions: Temperature and humidity during incubation must be well managed. Deviation from the specified parameters leads to inaccurate bacterial growth rates for misleading results.
• Ensure uniform inoculation : Apply the bacterial suspension evenly and place the sterile cover film carefully to maintain full surface contact.
• Validate neutralization step :The neutralizer must effectively stop antibacterial action after incubation. If not validated, results may falsely appear stronger.
• Accurate calibration of instruments: All equipment used, such as a colony counter or incubator, must be calibrated periodically to provide accurate readings while testing the product.

For more details, refer to the ISO 22196 test procedure