Key summary
- Purpose & Scope : ISO 22196 and ASTM E2180 are utilized to test the antimicrobial properties of plastics and polymeric materials, though they differ in scope, organisms and test conditions.
- Test Conditions : ISO 22196 involves high humidity for testing in wet use conditions. On the other hand, ASTM E2180 is performed under relatively lower humidity conditions using an agar slurry inoculum.
- Selection of organisms differs between ISO and ASTM : ISO and ASTM differ in the selection of test organisms. ISO 22196 involves the usage of standardized test organisms like Escherichia coli and Staphylococcus aureus. On the other hand, ASTM E2180 involves a wide variety of test microorganisms.
- Choosing the Right Standard : The selection of the right standard depends on how it will be utilized, the organisms to which it will be exposed and the claims to be made.
Summary
ISO 22196 and ASTM E2180 are standardized tests used to measure antibacterial activity in plastics and non-porous materials. ISO 22196 is best used for flat surface treated plastics, whereas ASTM E2180 is best used for hydrophobic or embedded antimicrobial polymers. The correct test to be used depends on the surface type, antimicrobial integration and target market requirements.
Why This Matters for Manufacturers
At first ISO 22196 and ASTM E2180 seem like similar testing standards for antibacterial plastics and polymeric materials.
But, they are not.
The wrong testing method can lead to:
- Inaccurate data that does not correctly represent product performance
- Regulatory statements that do not satisfy consumer or customer needs
- Delays in approval by purchasing groups or regulations
- Over- or under-statement of antibacterial performance claims
What ISO 22196 Measures?
ISO 22196 measures antibacterial activity on non-porous plastic surfaces.
How it works
- A known concentration of bacteria is applied directly onto the plastic surface.
- The surface is covered with a film to ensure uniform contact.
- Inoculated samples are incubated for 24 hours at high humidity.
- Surviving bacteria are recovered and quantified.
- The reduction is expressed as an R value (log reduction).
What ASTM E2180 Measures?
ASTM E2180 measures the antimicrobial effectiveness of agents incorporated into or chemically bound to predominantly flat (two-dimensional) hydrophobic or polymeric, surfaces.
How does it work?
- Bacteria are added to an agar slurry.
- The slurry is then applied to the test material and incubated for 24 hours
- Post incubation, remaining microbes from test sample are recovered using a neutralizing solution.
- Neutralized solution is serially diluted, plated and incubated.
- Antimicrobial activity is calculated by comparing bacterial reduction in treated vs untreated samples.
Key Technical Differences Between ISO 22196 and ASTM E2180
1. Contact Method
ISO 22196 : Film Contact Method
A liquid bacterial suspension is placed directly on the plastic surface and covered with a sterile film to ensure uniform, close contact under high humidity
ASTM E2180: Agar Slurry Method
Bacteria are incorporated into a semi-solid agar slurry and applied onto the surface, creating controlled but more realistic contact under relatively drier conditions
2. Moisture Conditions
ISO 22196 : High Humidity, Wet Environment
Incubation occurs under high humidity conditions to keep the interface wet between the bacteria and the material for 24 hours. This creates real-time conditions in which the material will be wet for a longer than usual time period. Wherein the material will be in constant contact with the bacteria.
ASTM E2180 : Semi-Solid, Controlled Moisture Simulation
The agar slurry holds the bacteria in place without the presence of a liquid film.It also does not require the presence of a liquid film to maintain contact, as the agar slurry holds the bacteria evenly distributed on the surface. During the test, humidity is maintained at greater than or equal to 75% to prevent drying out of the material.
3. Material Compatibility
ISO 22196 : Non-Porous Surfaces
It is mainly suitable for-
- Surface-treated plastics
- Coated consumer goods
- Flat medical components
ASTM E2180 : Hydrophobic or Embedded Antimicrobial materials
It is mainly suitable for:
- Polymeric materials
- Hydrophobic plastics
- Materials with incorporated antimicrobial additives
4. Standard Test Organisms
ISO 22196 commonly uses:
- Staphylococcus aureus
- Escherichia coli
ASTM E2180 specifies:
- Staphylococcus aureus ATCC 6538
- Pseudomonas aeruginosa ATCC 15442
- Klebsiella pneumoniae ATCC 4352
- Other microorganisms such as yeast or fungal conidia may also be tested using this procedure. Exposure periods may be modified (up to 96 h) to address more resistant microorganisms.
Can results from ISO 22196 be compared with ASTM E2180?
Clear answer is –
- No direct comparison
- Different inoculation systems
- Different moisture dynamics
- Different antimicrobial interaction mechanisms.
Key technical differences:
| Parameter | ISO 22196 | ASTM E2180 (2018) |
| Primary Purpose | Measures antibacterial activity on non-porous plastic surfaces | Quantitatively evaluates incorporated or bound antimicrobial agents in polymeric or hydrophobic materials |
| Material Type | Flat, non-porous plastics | Hydrophobic plastics, polymeric materials, epoxy resins, embedded-agent systems |
| Antimicrobial Type Best Suited For | Surface-treated or coated plastics | Hydrophobic polymers, plastics, materials |
| Humidity conditions | High humidity (โฅ 90%) | โฅ75% humidity |
| Test Organisms (Commonly Used) | Staphylococcus aureus, Escherichia coli | Staphylococcus aureus ATCC 6538, Pseudomonas aeruginosa ATCC 15442 or Klebsiella pneumoniae ATCC 4352, optional yeast/fungi |
| Result Expression | Log reduction (R value) | Percent reduction (calculated from geometric mean CFU counts) |
| Regulatory & Market Acceptance | Globally recognized ISO method | Widely accepted in US and industrial sectors |
Where Companies Often Get It Wrong
- Instead of selecting a test that validate the products for its intended uses companies select test methods based on marketing trends
- Not taking into account the relevance of the organisms to the targeted risk
- Using one test to support claims that should be tested with a different exposure model.
- Treating compliance as a checklist, not relating it to the function of the product.
How to choose the right standard for your product: ISO 22196 vs ASTM E2180?
Manufacturers need to consider a few factors-
- Specific regulatory requirements
- Material of the product to be tested and
- Scope of applications
Regulatory and claim considerations
Antimicrobial test selection is not just technical. It directly affects what you can legally claim.
Regulators and procurement teams actually assess –
- What type of claim is being made, is it antibacterial or antimicrobial surface?
- What is the environment in which the product is to be used? Is it wet, dry or in a healthcare or consumer setting?
- Is there a level of public health benefit implied in the claim?
- Is the data supporting the claim robust and relevant?
For plastics and consumer products with claims for antibacterial surface activity, ISO 22196 is an internationally recognized standard and also frequently referenced within regulatory dossiers. For the U.S. and industrial sector, ASTM E2180 is widely accepted for plastics and consumer products that contain hydrophobic polymers or embedded antimicrobial agents.
Why Choose MIS for ISO 22196 or ASTM E2180 Testing?
At Microbial Investigations Switzerland (MIS), we provide our clients with comprehensive testing solutions that meet the standards of ISO 22196 and ASTM E2180. With our cutting-edge technology and team of dedicated microbiologists, we make sure to comply with international standards to provide our clients with accurate and reliable results.
Are you in need of ISO 22196 and ASTM E2180 testing for your products? Talk to our experts here.
Conclusion
ISO 22196 and ASTM E2180 are not competing standards, they are complementary validation methods.
Choosing the right test depends on –
- Material type
- Intended application
- Duration of antimicrobial expectation
- Regulatory and claim requirements
FAQs
Q1: What is ISO 22196 and how does it test antibacterial activity on plastics?
ISO 22196 tests antibacterial properties in plastics. In this process, a suspension of bacteria is applied to the surface to be tested and covered with a film. After that, the surface is incubated for 24 hours. Post incubation, the reduction in bacteria on test samples is compared with a control.
Q2: How does ASTM E2180 differ from ISO 22196 in testing antibacterial plastics?
ASTM E2180 uses an agar-based inoculum to challenge the efficacy of antibacterial samples, creating controlled low-moisture contact with the sample surface. In the case of ISO 22196, the sample is challenged with liquid bacterial suspension covered with a film and incubated under high humidity conditions.
Q3: Which bacteria are tested in ISO 22196 and ASTM E2180?
ISO 22196 tests Escherichia coli and Staphylococcus aureus. ASTM E2180 includes Escherichia. coli, Staphylococcus. aureus, Pseudomonas. aeruginosa, Klebsiella. Pneumoniae. Fungi or yeasts can also be tested under ASTM E2180
Q4: Can results from ISO 22196 and ASTM E2180 be compared directly?
No. Different inoculation & contact methods in ISO 22196 & ASTM E2180 make it difficult to compare the results Each standard provides validation for antibacterial properties in its own way.
Q5: How should a manufacturer decide between ISO 22196 and ASTM E2180?
Based on surface type, target microbe, application areas, durability needs & market acceptance. ASTM E2180 is used for hydrophobic or antimicrobial agents incorporated into hydrophobic materials or polymeric surfaces Whereas, ISO 22196 is used for flat, antimicrobials coated plastic surfaces.
Q6: Which standard is more suitable for non-porous plastic products?
ISO 22196 would be more appropriate for non-porous plastic products, which include kitchenware, consumer products, medical device parts and similar products.
