Comparison of in vitro disc diffusion and time kill-kinetic assays for the evaluation of antimicrobial wound dressing efficacy

Authors

  • Corrie L. Gallant-Behm BSc,

    1. From the Departments of Microbiology and Infectious Diseasesa and Biologyb, University of Calgary, Calgary, Alberta, Canada; Nucryst Pharmaceuticals Corporationc, Fort Saskatchewan, Canada; Department of Chemical and Materials Engineeringd, University of Alberta, Edmonton, Alberta, Canada; and Departments of Surgery (Plastic)/Microbiology and Immunologye, University of Texas Medical Branch and Shriners Burns Institute for Children, Galveston, Texas.
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  • a Hua Q. Yin MD, PhD,

    1. From the Departments of Microbiology and Infectious Diseasesa and Biologyb, University of Calgary, Calgary, Alberta, Canada; Nucryst Pharmaceuticals Corporationc, Fort Saskatchewan, Canada; Department of Chemical and Materials Engineeringd, University of Alberta, Edmonton, Alberta, Canada; and Departments of Surgery (Plastic)/Microbiology and Immunologye, University of Texas Medical Branch and Shriners Burns Institute for Children, Galveston, Texas.
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  • c Shijie Liu PhD,

    1. From the Departments of Microbiology and Infectious Diseasesa and Biologyb, University of Calgary, Calgary, Alberta, Canada; Nucryst Pharmaceuticals Corporationc, Fort Saskatchewan, Canada; Department of Chemical and Materials Engineeringd, University of Alberta, Edmonton, Alberta, Canada; and Departments of Surgery (Plastic)/Microbiology and Immunologye, University of Texas Medical Branch and Shriners Burns Institute for Children, Galveston, Texas.
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  • d John P. Heggers PhD,

    1. From the Departments of Microbiology and Infectious Diseasesa and Biologyb, University of Calgary, Calgary, Alberta, Canada; Nucryst Pharmaceuticals Corporationc, Fort Saskatchewan, Canada; Department of Chemical and Materials Engineeringd, University of Alberta, Edmonton, Alberta, Canada; and Departments of Surgery (Plastic)/Microbiology and Immunologye, University of Texas Medical Branch and Shriners Burns Institute for Children, Galveston, Texas.
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  • e Rita E. Langford BSc,

    1. From the Departments of Microbiology and Infectious Diseasesa and Biologyb, University of Calgary, Calgary, Alberta, Canada; Nucryst Pharmaceuticals Corporationc, Fort Saskatchewan, Canada; Department of Chemical and Materials Engineeringd, University of Alberta, Edmonton, Alberta, Canada; and Departments of Surgery (Plastic)/Microbiology and Immunologye, University of Texas Medical Branch and Shriners Burns Institute for Children, Galveston, Texas.
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  • c Merle E. Olson DVM,

    1. From the Departments of Microbiology and Infectious Diseasesa and Biologyb, University of Calgary, Calgary, Alberta, Canada; Nucryst Pharmaceuticals Corporationc, Fort Saskatchewan, Canada; Department of Chemical and Materials Engineeringd, University of Alberta, Edmonton, Alberta, Canada; and Departments of Surgery (Plastic)/Microbiology and Immunologye, University of Texas Medical Branch and Shriners Burns Institute for Children, Galveston, Texas.
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  • a David A. Hart PhD,

    1. From the Departments of Microbiology and Infectious Diseasesa and Biologyb, University of Calgary, Calgary, Alberta, Canada; Nucryst Pharmaceuticals Corporationc, Fort Saskatchewan, Canada; Department of Chemical and Materials Engineeringd, University of Alberta, Edmonton, Alberta, Canada; and Departments of Surgery (Plastic)/Microbiology and Immunologye, University of Texas Medical Branch and Shriners Burns Institute for Children, Galveston, Texas.
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  • and a Robert E Burrell PhD b,d

    Corresponding author
    1. From the Departments of Microbiology and Infectious Diseasesa and Biologyb, University of Calgary, Calgary, Alberta, Canada; Nucryst Pharmaceuticals Corporationc, Fort Saskatchewan, Canada; Department of Chemical and Materials Engineeringd, University of Alberta, Edmonton, Alberta, Canada; and Departments of Surgery (Plastic)/Microbiology and Immunologye, University of Texas Medical Branch and Shriners Burns Institute for Children, Galveston, Texas.
      Dr. Robert E. Burrell, Room 524, Chemical and Materials Engineering Building, University of Alberta, Edmonton, Alberta, T6G 2G6 Canada. Fax: (780) 492-2881; Email: Robert.burrell@ualberta.ca.
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Dr. Robert E. Burrell, Room 524, Chemical and Materials Engineering Building, University of Alberta, Edmonton, Alberta, T6G 2G6 Canada. Fax: (780) 492-2881; Email: Robert.burrell@ualberta.ca.

Abstract

There is a plethora of new silver-containing dressings on the market today. Various manufacturers attempt to show that their dressings are the most efficacious and therefore should be preferentially employed by health care workers based on the results of their in vitro tests. However, there have been no studies that clearly identify which tests are appropriate for comparison purposes. The purpose of this study was to determine which in vitro test is most appropriate for evaluating the antimicrobial efficacy of silver-containing dressings. This was done by testing seven silver-containing dressings and two non-silver-containing topical agents against 17 clinically relevant microorganisms using zone of inhibition assays and time-kill kinetic assays in complex media. The results for the two assays were then correlated to determine whether the methods generated similar results. It was determined that the two methods do not correlate at all. This is most likely a result of the silver interacting with the media in the zone of inhibition test, thus invalidating the results of this test. We therefore conclude that zone of inhibition data generated for silver-containing dressings is of little value when assessing antimicrobial efficacy and that time-kill assays are of greater use.

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