Antimicrobial Efficacy Testing of Treated Wound Dressings

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Treated Wound Dressing Antimicrobial Efficacy Testing

Microchem Laboratory is a leader in Antimicrobial Fabric and Textile Testing.

The laboratory understands federal and state antimicrobial product regulations and works with clients to rapidly and cost-effectively bring new products to market. In addition, Microchem can help identify opportunities for existing antimicrobial fabrics and textiles.

Antimicrobial Wound Dressing Background

According to a 2015 review article2, there are over 3000 types of dressings available to addressing multiple aspects of wound care. Modern antimicrobial wound dressings have been designed to keep the wound hydrated and promoting healing in addition to covering and protecting the wound from external contamination. Antimicrobial or Interactive dressings, that act as a pathogen barrier for the wound, typically are in the form of films, foams, hydrogels or hydrocolloids. Wound dressings can be used as primary dressings for acute wounds from injury or surgery, as a means to hold primary dressings in place, or as wound packing. From a regulatory perspective, wound dressings are considered Class II medical devices.

Wounds provide a perfect environment for bacterial colonization and biofilm formation, supplying both a growth surface and nutrients to sustain growth. It has been shown that multiple types of pathogenic biofilm producing bacteria such as S. aureus and P. aeruginosa can grow unchallenged within the wound dressing environment, but that antimicrobial wound dressings can limit, but may not eradicate, bacterial growth.2

According to an FDA Guidance Document for Wound Dressings3 in addition to demonstrating the ability to provide a physical barrier from a broad spectrum of microorganisms (Barrier Testing), manufacturers of wound dressings are recommended to perform quantitative biochemical testing, following ASTM E2315-03 or an equivalent method to specifically address the risk of infection. This is discussed on the Wound Dressing Microbial Ingress Test page.

Wound Dressing Antimicrobial Efficacy Testing Summary

In the case of wound dressings that contain antimicrobial agents, manufactures need to support their claims that the antimicrobial agent provides an additional clinical benefit. The FDA recommends performance testing (Bench Testing, Animal Studies, and Clinical Studies) to demonstrate the antimicrobial effectiveness of the antimicrobial agent on treated medical devices such as antimicrobial wound dressings.4 The Bench, or in vitro Testing, should simulate the clinical use of the device mimicing exposure conductions such as temperature, preconditioning the device with body fluid, dynamic environment, body contact time, and microorganism contact time. Representative “normal flora and relevant clinical isolates” that are within 1-2 passages of the original isolation are recommended. The control dressing should be identical to the antimicrobial dressing, minus the antimicrobial agent. The effects of antimicrobial concentration and potential elution of the antimicrobial with respect to the dressing’s antimicrobial effectiveness as well as the effect of the antimicrobial on the dressing surface, integrity, stability and durability should be assessed. All test methods (inoculation and recovery techniques, use of neutralizers, recovery media, incubation temperature, incubation time) must be described.

For textile wound dressings, the AATCC 100 – Antimicrobial Fabric Test can be used. Wound dressings that contain gels typically use the ASTM E2315 – Liquid Suspension Time-Kill Test and the Minimum Inhibitory Concentration Test (MIC) to meet these requirements.

Strengths of Wound Dressing and Antimicrobial Efficacy Testing

Completion of antimicrobial efficacy testing will evaluate if there is an enhanced ability of the test device to prevent the transmission of microbial contamination. Sponsors will be able to report this data with confidence and it can be submitted as part of the requirements suggested by the FDA.

The ASTM E2315 quantitative time-kill tests are relatively inexpensive, the test parameters are easy to control in the laboratory setting, and the benefit of the dressing including an antimicrobial species can be evaluated and the results compared with those of other products or controls.

The AATCC 100 test method is also quantitative, reproducible test that can be used for growth-inhibiting and bacteria-killing properties.

The MIC test is a straightforward, reproducible test that can be completed on a very small scale with very quick turnaround times.

Weaknesses of Wound Dressing Microbial Ingress Testing

As with any test method that simulates actual use, it is challenging to take all “real life” factors into account, and the test results will have limitations due to the assumptions used for the testing protocol. Microchem will work with the sponsor to identify appropriate procedures and test conditions for testing protocols in order to best replicate use during actual patient procedures.

Why Microchem?

Since 1988 Microchem Laboratory has served industry needs as an EPA and FDA GLP-compliant testing organization with a wide array of product and customer tailored testing services for environmental surface disinfectants, high-level disinfectants, sanitizers, medical devices, antimicrobial surfaces, personal care products, and antimicrobial devices. Our skilled, highly experienced microbiologists and chemists are ready to collaborate with you to evaluate the performance of your antimicrobial devices with regards to microbial ingress. Microchem can help speed your project to completion.

Our microbial ingress studies are conducted following the guidance provided by the FDA1 in accordance with Good Laboratory Practice Standards (GLPs) stipulated by U.S. FDA 21 CFR 58. In addition, studies are conducted in accordance with Microchem Laboratory’s Quality Management System and undergo a full quality assurance review. All studies by Microchem Laboratories are conducted in accordance with general terms and conditions as posted on


Wound Dressings – A Review. Biomedicine (Taipei). 2015 Dec; 5(4): 22. S. Dhivya et al.

Testing wound dressings using an in vitro wound model. J. Wound Care. 2010 June; 19(6):220-226. C. Lipp et al.

Guidance for Industry and FDA Staff – Class II Special Controls Guidance Document: Wound Dressing with Poly(diallyl dimethyl ammonium chloride) (pDADMAC) Additive. October 6, 2009. U.S. Food and Drug Administration.

Draft Guidance for Industry and FDA Staff Premarket Notification [510(k)] Submissions for Medical Devices that Include Antimicrobial Agents, July 19, 2007.