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ASTM E2315: 2016 – Standard Test Method for Time-Kill Antimicrobial Activity
ASTM E2315-16 defines a standard approach for the determination of the reduction in the number of viable microorganisms after a specified time following exposure to the antimicrobial test material. This time-kill test provides crucial data regarding the efficacy of an antimicrobial agent to kill or inhibit microbial growth, thus making it a basic component of the development and validation process of antimicrobial agents. The standard ensures consistent and reproducible test conditions for the validation of the biocidal efficacy of disinfectants and topical antiseptics intended to be used in industries where sterilization and disinfection are crucial.
The test is often carried out using various microorganisms including bacteria, fungi, and yeasts, thus offering a wide scope applicability in other industries. Whether for health care, consumer products, or industrial applications, ASTM E2315-16 provides a reliable method to determine the effectiveness of antimicrobials.
Products tested using ASTM E2315 test method
This test method can be used to determine the antimicrobial efficacy of various products such as antibacterial liquid soaps, mouthwashes, disinfectants, hand sanitizers, surgical scrubs, and other topical preparations intended for skin application.
ASTM E2315 Test Conditions and Requirements
Test conditions | |
Bactericidal activity Yeasticidal activity Fungicidal activity | Mandatory test organisms |
Pseudomonas aeruginosa (ATCC 15442) Staphylococcus aureus (ATCC 6538) Enterococcus hirae (ATCC 10541) Escherichia coli (K12) (NCTC 10538) Additional strains as per customer request Candida albicans (ATCC 10231) Saccharomyces cerevisiae Aspergillus brasiliensis (ATCC 16404) | |
Contact time | 15 seconds, 30 seconds, 60 seconds, or any time range from several minutes to hours. |
Temperature | 25 °C Additional temperatures are given depending on the intended use of the test product: Room temperature: 22 ± 2°C Human skin: 30 ± 2°C Warm water: 38 ± 2°C |
The test organisms chosen can be indicative of the microbial population found in the specific conditions in which the test product is used or may represent standardized strains.
ASTM E2315 test methodology
Inoculum preparation
- For bacteria, 24-hour-old cultures cultivated in nutrient broth are used for the experiment. For fungi, spore preparation from a saline wash can be used.
Inoculation and neutralization
- The inoculum suspension (usually 1/10 of the product volume) is mixed with the test material, ensuring uniform dispersion.
- At predetermined time intervals (e.g., 30 seconds, 60 seconds), aliquots (typically 1 ml) are removed from the test mixture and neutralized to quench the antimicrobial activity of the test product.
- To determine the initial microbial concentration, a saline control is inoculated with the same test microbes.
Incubation
- The number of viable organisms from appropriate dilutions is enumerated using the spread plate or pour-plate technique.
- The plates are then incubated for 24-48 hours at a specified temperature.
Enumeration
- The microbial population is enumerated and expressed in terms of CFU/mL.
- The initial and final counts in the microbial population are compared to determine the log10 reduction and percent reduction.
Compliance and industry standards for ASTM E2315 test
Many industries must comply with ASTM time kill test to achieve regulatory compliance. Testing helps products meet industry-specific requirements for antimicrobial efficacy provided by regulatory agencies such as the FDA, EPA, and various other regulatory bodies. Through thorough testing, manufacturers will be able to validate the antimicrobial claims of their products which can be used as an added factor to gain consumer trust in a crowded market.
Applications of Time-kill test methods
The time kill test method is applicable to a wide range of industries. Key sectors that benefit from this testing include:
Healthcare: for disinfectants, hand sanitizers, and antimicrobial surfaces.
Consumer products: for personal care goods, cleaning agents of households, and apparel.
Industrial: For coatings, biocides, and cleaning agents in manufacturing environments.
Importance of ASTM E2315 testing for antimicrobial products
The time kill test plays a significant role in medical settings and industrial sectors. It provides a standard method to determine the kill rate of microbes thus helping in improving formulations to provide better efficacy rates. Thus, testing the products for antimicrobial efficacy indirectly contributes to safeguarding consumer health.
Benefits of ASTM E2315 time-kill test method
Regulatory compliance
- Testing provides the necessary data required for regulatory compliance and speeds up the approval process of your disinfectants in various markets.
Competitive advantage
- Testing allows you to provide evidence-based performance data which can differentiate your products from competitors.
- It enhances customer confidence in the effectiveness of your disinfectants.
Product development and improvement
- The results obtained from the test help identify areas where formulations can be optimized for better efficacy.
Liability protection
- Testing provides documented evidence of product efficacy thus reducing the risk of legal issues related to product performance and safety.
Strengths of Time-kill test
The strengths of the time kill test method include its ability to:
- Provide quantitative data on antimicrobial efficacy.
- Assess a wide range of microorganisms and products.
- Offer reproducible and standardized results.
- Support compliance with regulatory requirements.
Conclusion: The role of ASTM E2315 in antimicrobial product testing
The time kill test is a significant standard for the evaluation of antimicrobial products. The standardized protocols help manufacturers demonstrate their products’ efficiencies in mitigating antimicrobial contamination. Manufacturers must stay updated with the appropriate industry standards and regulations and increase the competitiveness of their products. With its broad applicability across various industries, ASTM time kill test remains a cornerstone in antimicrobial product testing.
At Microbe Investigations Switzerland, we assist our customers in identifying the antimicrobial efficacy of their products. Our highly qualified microbiologists follow systematic testing procedures in accordance with ASTM E2315 guidelines. Equipped with top-notch instruments and advanced facilities, our labs ensure a meticulous antimicrobial evaluation process by significantly reducing the likelihood of errors.
To schedule a consultation or learn more about ASTM E2315 testing, please contact us here.
FAQs
ASTM E2315 is a quantitative suspension-based test method used to assess the reduction in aerobic microbial population within a specified sampling time when tested against antimicrobial products.
The time-kill test is a method used to evaluate the antimicrobial activity of a test material by measuring the reduction in the number of viable microorganisms over a specified period.
The standard can be used for testing any liquid finished product, for example, hand sanitizers, antibacterial liquid soaps, mouthwash, feminine wash products, disinfectant cleaning products, and more.
It takes 3 – 5 weeks depending on the test organism to complete the test.
At MIS, we perform this test using the following microbial strains: Pseudomonas aeruginosa (ATCC 15442), Staphylococcus aureus (ATCC 6538), Enterococcus hirae (ATCC 10541), Escherichia coli (K12) (NCTC 10538), Candida albicans (ATCC 10231), Saccharomyces cerevisiae (ATCC ), Aspergillus brasiliensis (ATCC 16404). Additional strains can be added at the customer’s request.
The test method evaluates antimicrobial activity by measuring the changes in a population of viable aerobic microorganisms within a specified sampling time when the antimicrobial test materials are present.
Microbial reductions are measured by counting the surviving organisms after exposure to the test material. The colony counts (recorded as CFU/ml) are converted to log10 scale, and the log10 reduction is calculated by comparing with initial microbial population.
The test helps in product development by providing reliable data on the antimicrobial efficacy of new formulations, guiding the optimization of product formulations. It ensures product quality by verifying that each batch of product meets the specified antimicrobial standards.
This test supports regulatory compliance by providing standardized, reliable data that meets the requirements of regulatory authorities. Manufacturers can use the test reports to scientifically validate their product claims.
Regular testing is recommended to ensure consistent product performance and quality over time.
Certification ensures product efficacy and safety, supports regulatory compliance thus facilitating market approval, and provides a competitive advantage in crowded markets.
Log reduction is quantified as the degree of reduction of microbial population. The higher the log reduction value, the greater the effectiveness of the antimicrobial product in killing or inhibiting microbial growth.
Yes, the time kill test can be tailored to test a variety of microbial strains, including bacteria, fungi, and yeasts.
No, This standard is not applicable for food safety testing. It mainly deals with testing antimicrobial products that include disinfectants, sanitizers, hand washes and others.
Neutralizers are used at fixed intervals of time for example 30 seconds, 1 minute, to stop the antimicrobial activity of the test product.
Some common difficulties in carrying out the time kill test procedure are choosing appropriate neutralizers, having consistent microbial inoculum, and simulating real-world conditions during the test.
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