In today’s health-conscious world, many consumer products claim to be antibacterial, but how can we be sure that these claims are valid? Verifying the effectiveness of such products requires a standardized method. ISO 22196 is an international standard that provides a rigorous testing procedure to certify whether plastic materials used in healthcare, food industry packaging, and other industries truly possess antibacterial properties, ensuring that products meet safety and hygiene expectations in a reliable and transparent way. Here we deliver information about ISO22196 testing for plastics, including the test organisms, the test method and the passing criteria for certifying the plastic products as antibacterial.

Purpose

ISO 22196 determines the antibacterial performance of plastic materials, used in various sectors of industry: health, food packaging, and consumer goods. It provides a way to quantify the antibacterial property of plastic surfaces. Thus, it gives a standardized means to address the challenges posed by bacterial contamination on non-porous materials such as plastics. This makes sure that the products meet the requirements for hygiene and safety, protecting consumers from potential health risks.

Objective

ISO22196 testing for plastics aims to provide a consistent and reproducible method for the assessment of the antibacterial activity of plastic materials. In this respect, the efficacy is quantified by its ability to inhibit bacterial growth. The process gives manufacturers a means of validating the antibacterial claims made for their products and ensure the product’s efficacy and suitability for use in contamination-critical environments.

Principle 

The principle of ISO 22196 testing for plastics involves inoculation of the plastic surface with a known amount of bacteria followed by incubation under controlled conditions. This is followed by enumeration of bacterial population after a set period, usually after 24 hours. The antibacterial activity is then expressed on a logarithmic scale. 

How is ISO 22196 Test Method Performed?

The test method for ISO22196 testing for plastics involves several key steps:

1.Preparation of Test Specimens: Plastic samples are cleaned and sterilized. Control(untreated) samples are also prepared for comparison.

2. Inoculation: The bacterial suspension of known volume/ concentration is spread uniformly on the plastic surface. It ensures equal exposure of bacteria throughout the surface of the material.

3. Incubation: The plastic samples in contact with the inoculum are incubated under controlled temperature and humidity for 24-hour duration. The incubation environment is the simulation of the natural conditions.

4. Neutralization: A neutralizing solution is applied to stop further antibacterial action, ensuring the remaining viable bacteria can be accurately counted. The neutralizing solution should be used as per manufacturers’ instructions. 

5. Quantitative Measurement: The number of bacteria that survived on the surface after incubation is measured using a colony-counting method. This is compared with the bacterial load carried by an untreated plastic sample to access the antibacterial efficacy.

Test conditions and requirements 

Specific Test Organism

The ISO22196 testing for plastics is generally performed with two common bacterial strains that are prevalent in causing risks in healthcare and food industry settings:

• Staphylococcus aureus: Staphylococcus aureus is commonly found on plastic surfaces, especially in places like hospitals, public spaces, and food handling areas, where it can survive for long periods, hence posing contamination and infection risks.

• Escherichia coli (E. coli): The resistance test of plastics against E. coli is carried out because it is one of the most common bacteria threatening the food safety.

These strains are selected because they pose a high level of threat to human health and are found extensively in environments susceptible to bacterial contamination.

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). This temperature simulates optimal bacterial growth conditions, similar to human body temperature or warm environments where bacterial contamination is a concern.

Humidity: The relative humidity during the incubation period is maintained at ≥ 90%. High humidity levels help ensure bacterial growth and activity during the incubation period, providing an optimal environment for the test bacteria.

Passing Criteria

The passing criteria as per ISO 22196 includes  demonstration of a substantial inhibition in the increase of bacterial count, in comparison to an untreated control. The reduction is expressed as an antibacterial activity value (R). This is calculated based on the logarithmic difference between the bacterial count on the untreated surface and that on the treated surface. The passing criteria for ISO22196 testing for plastics are as follows:

• R ≥ 2.0: This indicates a 99% reduction in bacterial count, which is the bare minimum a material must achieve to be effective.

• Log Reduction: The test results are often reported in terms of log reduction, where a 3-log reduction represents a 99.9% reduction in bacterial count, and a 5-log reduction represents a 99.999% reduction.

The product must attain 3-log reduction to pass the test of possessing antimicrobial property.

Factors/ 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 infection 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.

• Handling of Test Specimens: The ISO22196 testing for plastics involves handling the specimen  using gloves and sterile tools so that  transfer of bacteria from one specimen to another may not occur and also to ensure bacteria are only introduced through the controlled inoculation process.

• Consistent Application of Bacteria: This must be done in such a way that the bacterial suspension spreads homogeneously on the plastic surface. Otherwise, due to non-homogenous inoculation, consistent bacterial growth might not take place, thereby giving unreliable results.

• 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.

Benefits of ISO 22196 Testing

Ensuring Public Health and Safety

ISO22196 testing for plastics ensures the manufacturing company that their plastic products don’t support bacterial contamination of any kind thus saving public health. This is most critical in a healthcare setting where the patients are prone to bacterial contamination, leading to infections. In food processing and packaging, the use of such antibacterial plastics ensures that foodborne illnesses are restricted, thus making safety for consumer goods to be uplifted.

Compliance with Regulatory Requirements

Many industries are required to comply with stringent hygiene and safety regulations. ISO22196 provides a standardized test method to test the antibacterial efficacy of the manufactured product in order to meet the regulatory requirements and to show that their products are safe to be put into service for any given environment where hygiene is critical. This can be especially important in obtaining certifications for use in healthcare and food-related applications.

Increased Consumer Confidence

There is a growing demand for products with antibacterial properties. ISO 22196-tested materials marketed as safer and more hygienic would give a competitive edge in the marketplace. Marketing plastic products as antibacterial will gain customers. 

ISO22196 testing for plastics plays a critical role in the assurance of safety and antibacterial efficiency for  plastic materials manufactured with such claims. Standardized testing methods are available for manufacturers to prove the effectiveness of their antibacterial treatments, which can improve consumer confidence and reduce potential legal and regulatory issues associated with it. Since hygiene is crucial in today’s world, ISO 22196 testing will be of primary importance for every industry dependent on plastic materials.

If your products need to be validated for antibacterial properties, Microbe Investigations Switzerland (MIS) offers comprehensive ISO22196 testing for plastics materials. Contact MIS today to learn more about how we can help you meet your testing and validation needs.