Biocides are chemical or biological agents which are applied to eliminate the presence of harmful organisms. They can range from bacteria and viruses to fungi and pests. These products are particularly important for public health, agricultural, and industrial use for reducing or eliminating harmful pathogens. However, to ensure their effectiveness, rigorous efficacy testing should be conducted to confirm that the product is capable of killing or inhibiting the growth of target microorganisms thus meeting required regulatory requirements. The biocide testing process encompasses several laboratory testing methods according to various regulatory guidelines, which will be discussed in this article.
Key parameters in biocide efficacy testing
Biocide efficacy testing includes assessing its efficacy against target organisms and depends on several parameters. These parameters must be controlled to give accurate and consistent results.
Active ingredient concentration
- The activity of a biocide is determined by its concentration of active ingredients. In most cases, while higher concentrations may mean higher biocidal activity, it could also lead to toxicity and environmental problems. Several concentrations are usually tested to determine the minimum dose that is most effective.
Contact time
- This refers to the time that the biocide must stay in contact with the target organism. Short contact time can result in poor killing, while longer contact times may improve performance. Testing at different time intervals defines the optimum contact period required for maximum efficacy.
Temperature and pH
- Temperature and pH are other environmental factors capable of affecting the efficacy of biocides. Most of the biocides have an optimum temperature and a pH at which they are likely to work. Therefore, biocide testing at different conditions gives an insight into their efficacy.
Microbial spectrum
- Biocides are usually developed against specific organisms. These could be bacteria, viruses, or fungi. Testing needs to be done against a wide spectrum of microorganisms, including the most common field strains, to confirm that the biocide eliminates its target organisms.
Regulatory standards for biocide testing
Biocide efficacy testing must comply with specific regulatory standards to ensure the product’s safety and effectiveness. These standards vary by region and industry.
European Union standards (e.g., EN 14885)
- EN 14885 is one of the several European Standards that describe the test conditions and requirements to demonstrate the efficacy of disinfectants and antiseptics used for hand, surface, and instrument disinfection.
International standards (e.g., ISO 22196)
- ISO 22196 is an international standard test that determines antibacterial activity on non-porous surfaces. Biocides tested under this standard are evaluated for their ability to inhibit bacterial growth on materials such as plastic and other solid surfaces.
U.S. standards (e.g., EPA FIFRA)
- In the U.S., biocides are regulated under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), which is enforced through the Environmental Protection Agency (EPA). The EPA does not allow any biocides to be marketed without reliable proof of efficacy testing. The EPA also provides guidelines on testing methods and the conditions for biocide testing to determine their efficacy against different categories of microorganisms.
Common testing methods
Assessment of the efficacy of biocides includes different methodologies to test various aspects of product performance under controlled conditions.
Suspension tests (e.g., EN 1276, ASTM E2315)
- A suspension test is performed by adding a biocide to a known quantity of microorganisms in a liquid medium. Samples are withdrawn after a specified contact time, followed by neutralization, and then tested for a log reduction of microbes. This method is quite appropriate for evaluating disinfectants and sanitizers in their liquid form.
Surface tests (e.g., EN 13697)
- These tests are performed to assess biocidal efficacy on hard surfaces. In surface tests, biocides are applied to hard surfaces contaminated with microorganisms that correspond to real-world situations. After treatment, log reduction of microorganisms on the surfaces is calculated.
Carrier tests (e.g., EN 14561)
- In the carrier test, the effectiveness of a biocide on carriers such as cloth, glass, or metal is evaluated. The carriers are inoculated with microorganisms, treated with the biocide, and assayed for a reduction in microbial load. This method is frequently used for testing hospital disinfectants.
Field tests and real-world application testing
- In addition to laboratory testing, biocides must also be tested in a field setting or where they are intended to be applied. Field tests check a biocide performance under real conditions of environmental contamination, user application, and surface materials.
Laboratory conditions for biocide testing
Laboratory testing performed at accredited biocide testing labs ensures that the results are reliable and can be reproduced. In a laboratory, testing professionals can simulate the exact test conditions in which a given biocide will be used.
Controlled environments
- Laboratory tests are performed in a controlled environment with careful monitoring of temperatures, humidity, and pH. Biocide testing under controlled environments ensures that the results are free of external influences and are reproducible.
Test materials and surfaces
- Depending on the use of a biocide, several tests are conducted on various materials, including stainless steel, plastic, and textiles. Since different materials might have various effects on the biocide efficacy, tests must be conducted on the appropriate surfaces relevant to the application of the product.
Replicability of results
- Production of replicable results is one of the prime objectives of any laboratory test. This will ensure that the biocide works uniformly under divergent field situations and various conditions. Multiple trials are often conducted to verify the reliability of the data.
Interpreting biocide test results
The interpretation of biocide testing results is critical for understanding the product’s overall performance.
Defining successful efficacy
- A biocide is considered successful if it presents a significant reduction in microbial load, often reported in logarithmic reduction (log reduction). A reduction of 3-log means 99.9% of the microorganisms are killed, whereas a 6-log means 99.9999% of target organisms are killed.
Log reduction vs. complete kill
- In some cases, the biocides may not completely eliminate all microorganisms but may significantly reduce their concentration level to safe or acceptable levels. Proper knowledge of the difference between log reduction and complete microbial kill is important in assessing biocide efficacy.
Real-world relevance of laboratory results
- Though laboratory testing of biocides may be useful in gaining information about the performance of biocides, it cannot reflect reality at all times. Therefore, it is necessary to consider the relevance of these tests to application in everyday situations.
The need for ongoing testing and validation
Even after a biocide has been approved for use, ongoing biocide testing and validation are necessary to ensure continued efficacy over time.
Post-market surveillance
- Once a biocide makes its way into the markets, post-market surveillance enables tracking the real-life performance of the products. This assumes a high degree of importance in the case of such products that find applications in healthcare or food safety applications, wherein microbial resistance may develop.
Product longevity and resistance development
- Constant testing will allow for the determination of a reduction in the product’s effectiveness due to factors such as changes in microbial resistance or other environmental factors. Regular validation ensures that the efficacy of biocides is maintained throughout their lifetime.
Biocide efficacy testing is a complex process because several parameters must be taken into consideration, along with different test methods and regulatory standards. Testing accurately for their efficacy assures that biocides are effective and safeguard public health from the spread of pathogenic microorganisms. With the increasing demand for effective disinfectants and sanitizers, proper efficacy testing conducted at trusted biocide testing labs is more important than ever.
At Microbe Investigations Switzerland, we offer comprehensive biocide testing services to help you develop products that meet stringent regulatory requirements and deliver real-world efficacy. Contact us today to learn more about our biocide efficacy testing solutions.
