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Assessment of Antibacterial Finishes on Textiles
Antimicrobial agents are useful textile additives and have become more and more common in today's products. They provide textiles with remarkable resistance to odors caused by microorganisms, often without detracting from the appearance or feel of the fabric. With the social rise of more active lifestyles, the demand for fabrics with this specific technonology has become greater than ever. Not only is this key in the sports and commercial world, but even more important in the medical world. Some powerful antimicrobial textiles may prevent infections by killing contaminants of public health concern, such as MRSA, should they be deposited on the fabric.
Whether the antimicrobial agent is woven into the textile as a thread or applied to the textile surface as a liquid, testing is critical to ensure performance. Laundering is a main source of fabric degradation, so companies often request standardized laundering prior to AATCC 100 tests. Click here to learn about Microchem Laboratory's laundering services.
The AATCC 100 test method is the most commonly chosen test and has become the industry standard for antimicrobial fabric performance in the United States. Below, you will find a summary of the AATCC 100 test method, along with some of its strengths and weaknesses. The AATCC 100 test method method is designed to quantitatively test the ability of fabrics and textiles to inhibit the growth of microorganisms or kill them, over a 24 hour period of contact.
Summary of the AATCC 100 Test Method
- The test microorganism is grown in liquid culture.
- The concentration of the test microorganism is standardized.
- The microbial culture is diluted in a sterile nutritive solution.
- Control and test fabric swatches are inoculated with microorganisms.
- The inoculation is performed such that the microbial suspension touches only the fabric (see original method for details).
- Bacteria levels on both control and test fabrics are determined at "time zero" by elution in a large volume of neutralizing broth, followed by dilution and plating.
- A control is run to verify that the neutralization/elution method effectively neutralizes the antimicrobial agent in the fabric.
- Additional inoculated control and test fabrics are allowed to incubate, undisturbed in sealed jars, for 24 hours.
- After incubation, microbial concentrations are determined.
- Reduction of microorganisms relative to initial concentrations and the control fabric is calculated.
Strengths of the AATCC 100 Test Method
- The method is quantitative and results tend to be reproducible. Quantitative results can aid in determining the usage and marketability of the textiles tested.
- The method tests for both bacteriostatic (growth-inhibiting) and bactericidal (bacteria-killing) properties.
- Microbial concentrations are standardized, and bacteria are provided with nutrients during the incubation period, which provide them with ample opportunity to grow if fabrics aren't sufficiently antimicrobial. This is in contrast to certain other antimicrobial tests, where microbes are "incubated" in non-nutritive suspensions, which itself may be stressful over long periods. During this method, the microorganisms are provided with optimal conditions for growth, with only the textile and its technology there to affect it.
Weaknesses of the AATCC 100 Test Method
- The method has vague success criteria, meaning that whether or not a tested fabric qualifies as "antimicrobial" may ultimately be decided by the company sponsoring the study (the method states that "the criteria for success must be decided by the interested parties").
- The test can become cumbersome if the test fabric doesn't readily absorb liquids (hydrophobic).
Though the AATCC 100 Test has some minor drawbacks, it is an excellent way to quantify the antimicrobial activity level of an antimicrobial fabric. Among the various tests for antimicrobial activity of fabrics, it has emerged as the textile industry's standard.
Microchem Laboratory has years of experience performing antimicrobial testing. We highly recommend using the AATCC 100 Test method to quantify the bactericidal activity of antimicrobial fabrics. It is an excellent procedure to give accurate and reproducible results which allows clientele to gauge the proficiency of their product. Combined with Microchem Laboratory's experience and adaptability, this test method can be modified, maintaining scientific defensibility, in order to further challenge your technology, either with more aggressive parameters or against tougher microorganisms that might be more clinically relevant and suited to your product's end use and your company's testing objectives.