Effectiveness of a New Antimicrobial Gauze Dressing as a Bacterial Barrier

BACKGROUND: Gauze dressing continues to be the most commonly used wound dressing. However, because of its porous structure it is not a barrier to bacterial penetration. Binding an antimicrobial agent to the gauze fibers may prevent bacterial migration through the gauze and thus allow gauze to become a bacterial barrier. The purpose of this study was to evaluate the effectiveness of gauze treated with an antimicrobial agent to prevent external contamination from reaching the skin of normal volunteers. METHODS: 3 types of gauze were evaluated: gauze containing 0.2% polyhexamethylene biguanide (PHMB); gauze treated with iodophor solution (IG); and untreated gauze control (control). Twenty-four subjects were tested in 4 groups: PHMB vs. Control, PHMB vs. IG, PHMB vs. IG (1:10 in saline), and PHMB vs. IG (1:10 in broth). Each volunteer received 6 gauze sites on their back that were contaminated with 10 S. epidermidis and occluded for 24 hours before the gauze and underlying skin were quantitated for the challenge organism. RESULTS: No bacteria were detected in any of the PHMB gauze samples. Either no bacteria or only a few bacteria were detected on the skin beneath the PHMB gauze samples. In contrast, high numbers of challenge organisms were found in 92% of the control gauze samples and 100% of the underlying skin sites. Iodophor solution was effective in eradicating the challenge organisms unless the iodophor was exposed to protein in which case the antimicrobial activity of the iodophor was neutralized. CONCLUSIONS: Treating gauze with 0.2% PHMB prevented the migration of 10 bacteria through the gauze and kept underlying skin relatively free of bacteria. Binding PHMB to the gauze fiber was more effective than adding iodophor solution to the gauze in a protein-rich environment. These results indicate that binding 0.2% PHMB to gauze provides an effective barrier to bacterial penetration. INTRODUCTION Gauze dressing continues to be the most commonly used wound dressing. However, because of its porous structure, gauze is not a barrier to external bacterial penetration. Binding an antimicrobial agent to the gauze fibers may make the gauze an effective bacterial barrier since the bacteria would be killed on contact. Biguanides are an important class of antimicrobial agents with a long history of use in healthcare. The most commonly used biguanide in healthcare is chlorhexidine. Although chlorhexidine is a very effective antimicrobial, it is too cytotoxic for use in wounds. A modified biguanide that is more biocompatible is polyhexamethylene biguanide (PHMB). FDA has cleared the use of PHMB as an antimicrobial component in wound dressings under the pre-market notification (510k) process. The purpose of this study on human volunteers was to evaluate the ability of gauze treated with PHMB in the prevention of bacterial penetration. Effectiveness of a New Antimicrobial Gauze Dressing as a Bacterial Barrier Angelique M. Reitsma, M.D. and George T. Rodeheaver, Ph.D., University of Virginia Health System, Charlottesville, Virginia. MATERIAL AND METHODS Dressing material: Standard gauze dressing was impregnated with PHMB so that the final bound antimicrobial agent was 0.2% by weight. Since the antimicrobial agent is bound to the gauze, the wound tissue is not exposed to the agent. In this study the control dressing was the same gauze that had not been treated with any PHMB. Human volunteers: The study was conducted on healthy human volunteers who signed Informed Consent. The study was reviewed and approved by the Human Investigations Committee of the University of Virginia Health System. Volunteers had to be 18 years or older, and have dorsal skin that was intact, free of lesions or inflammation, and had minimal hair growth. Prior to enrollment, the dorsal skin of each volunteer was assessed by a scrubbing technique for the presence of penicillin-resistant microorganisms. Since the challenge organism in the study was a penicillin-resistant strain, any volunteer having a penicillinresistant organism already on their skin was excluded. Test procedure: The dorsal skin of each volunteer was scrubbed with iodophor antiseptic solution and subsequently rinsed with sterile saline, 1% neutralizer (thiosulfate solution), and finally 70% isopropyl alcohol. Six test sites were identified (3 experimental and 3 control). Using sterile technique each test site received a 1" X 1" gauze sample which was taped to the skin by 1/2" wide, waterproof tape. Each gauze sample first received 0.45 ml of wetting solution, then the surface of the saturated gauze was contaminated uniformly by adding dropwise 0.05 ml of saline containing 10, penicillin-resistant, Staphylococcus epidermidis (ATCC # 27626). After 10 minutes the gauze was occluded with an impermeable plastic film and held in place with an adhesive transparent film dressing. Each site was independent and self-contained. Twenty-four hours later the presence of the contaminating organism was quantitated in the gauze and on the skin surface below the gauze. Bacterial Quantitation Gauze Using aseptic technique, the gauze was exposed. With sterile scissors and forceps the gauze sample was cut along the tape edges and removed. The gauze sample (0.5" X 0.5") was immersed in 25 ml of sterile neutralizer solution and agitated with a mechanical shaker for 5 minutes. The number of challenge organisms remaining in the gauze was quantitated by standard serial dilution and plating techniques using selective trypticase soy agar containing 25 mcg/ml penicillin G. Results were reported as log 10 of colony forming units (CFU) per cm. The minimum detectable level of CFU in the gauze sample was 156 (log=2.19).