Purpose: Two commercially available bandage strips were chosen for this study. Both strips are marketed as a Curad® brand strip containing silver as the active ingredient, one had silver present on the absorbent pad, while the other contains silver in a gel residing on the pad. The purpose of this analysis was to determine the construction, silver release rates, % silver, and zones of inhibition for four different organisms using Kirby-Bauer testing for these silver bandage strips
Key
|
Bandage Number:
|
|
1
|
Curad® Silver
|
|
2
|
Curad® Silver Gel
|
Kirby Bauer Test Results:
The zone of inhibition calculation. The zone of inhibition for each bandage strip was calculated by subtracting the area of the observed clear zone around each pad from the area of the pad and reported in mm2. The results displayed are the average of two independent trials for each bandage strip.
In vitro antimicrobial activities of bandage strips. A modified Kirby-Bauer technique was used to assess the antimicrobial activity of each of the bandage strips. Four clinical isolates (Staphylococcus aureus ATCC 33591 (Methacillin Resistant- MRSA), Staphylococcus epidermis ATCC12228, Pseudomonas aeruginosa ATCC 9027, and Candida albicans ATCC 10231) were used in this study. Staphylococcus aureus (MRSA), Pseudomonas aeruginosa, and Staphylococcus epidermis were grown for 24 hours in Tryptic Soy Media at 37oC and diluted to 0.5 MacFarland Standard (equivalent to 1.5 x 108 CFU/mL). A cotton swab was placed in each suspension and pressed against the inside of the tube to remove excess liquid. Each swab was then used to streak a 150 X 15mm Mueller-Hinton agar plate. The plate was rotated by 90o and re-swabbed. The
rotation and swabbing process was repeated and the plate was allowed to dry for 3-5 minutes. The test bandage pads were then transferred to the agar plates using flame-sterilized forceps. The plates were then placed in an incubator at 37oC and held for 24 hours. In the case of Candida albicans, the same procedure was used with the exception that the organism was grown for 24 hours in Sabourand Dextrose media and
cultured on 100 x 15mm plates containing Sabourand Dextrose agar. At the end of 24 hours, the zone of inhibition was measured, and the pad was removed and transferred to a newly prepared culture plate. The test was repeated in this manner for a total of seven days.
|
|
Pseudomonas aeruginosa
(ATCC 9027)
Day # 1 - Pseudomonas aeruginosa (ATCC 9027)
|
Zone of Inhibition
|
|
|
Trial # 1
|
Trial # 2
|
Average
|
|
Bandage
|
Width (mm)
|
Length (mm)
|
Width (mm)
|
Length (mm)
|
Width (mm)
|
Length (mm)
|
Zone Area (mm2)
|
|
1
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0
|
|
2
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0
|
Day # 2 - Pseudomonas aeruginosa (ATCC 9027)
|
Zone of Inhibition
|
|
|
Trial # 1
|
Trial # 2
|
Average
|
|
Bandage
|
Width (mm)
|
Length (mm)
|
Width (mm)
|
Length (mm)
|
Width (mm)
|
Length (mm)
|
Zone Area (mm2)
|
|
1
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0
|
|
2
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0
|
Day # 3 -
Pseudomonas aeruginosa
(ATCC 9027)
|
Zone of Inhibition
|
|
|
Trial # 1
|
Trial # 2
|
Average
|
|
Bandage
|
Width (mm)
|
Length (mm)
|
Width (mm)
|
Length (mm)
|
Width (mm)
|
Length (mm)
|
Zone Area (mm2)
|
|
1
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0
|
|
2
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0
|
Day # 4 -
Pseudomonas aeruginosa
(ATCC 9027)
|
Zone of Inhibition
|
|
|
Trial # 1
|
Trial # 2
|
Average
|
|
Bandage
|
Width (mm)
|
Length (mm)
|
Width (mm)
|
Length (mm)
|
Width (mm)
|
Length (mm)
|
Zone Area (mm2)
|
|
1
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0
|
|
2
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0
|
Day # 5 -
Pseudomonas aeruginosa
(ATCC 9027)
|
Zone of Inhibition
|
|
|
Trial # 1
|
Trial # 2
|
Average
|
|
Bandage
|
Width (mm)
|
Length (mm)
|
Width (mm)
|
Length (mm)
|
Width (mm)
|
Length (mm)
|
Zone Area (mm2)
|
|
1
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0
|
|
2
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0
|
Day # 6 -
Pseudomonas aeruginosa
(ATCC 9027)
|
Zone of Inhibition
|
|
|
Trial # 1
|
Trial # 2
|
Average
|
|
Bandage
|
Width (mm)
|
Length (mm)
|
Width (mm)
|
Length (mm)
|
Width (mm)
|
Length (mm)
|
Zone Area (mm2)
|
|
1
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0
|
|
2
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0
|
Day # 7 -
Pseudomonas aeruginosa
(ATCC 9027)
|
Zone of Inhibition
|
|
|
Trial # 1
|
Trial # 2
|
Average
|
|
Bandage
|
Width (mm)
|
Length (mm)
|
Width (mm)
|
Length (mm)
|
Width (mm)
|
Length (mm)
|
Zone Area (mm2)
|
|
1
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0
|
|
2
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0
|
|
Staphylococcus aureus
(ATCC 33591)
Day # 1 -
Staphylococcus aureus
(ATCC 33591)
|
Zone of Inhibition
|
|
|
Trial # 1
|
Trial # 2
|
Average
|
|
Bandage
|
Width (mm)
|
Length (mm)
|
Width (mm)
|
Length (mm)
|
Width (mm)
|
Length (mm)
|
Zone Area (mm2)
|
|
1
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0
|
|
2
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0
|
Day # 2 -
Staphylococcus aureus
(ATCC 33591)
|
Zone of Inhibition
|
|
|
Trial # 1
|
Trial # 2
|
Average
|
|
Bandage
|
Width (mm)
|
Length (mm)
|
Width (mm)
|
Length (mm)
|
Width (mm)
|
Length (mm)
|
Zone Area (mm2)
|
|
1
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0
|
|
2
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0
|
Day # 3 -
Staphylococcus aureus
(ATCC 33591)
|
Zone of Inhibition
|
|
|
Trial # 1
|
Trial # 2
|
Average
|
|
Bandage
|
Width (mm)
|
Length (mm)
|
Width (mm)
|
Length (mm)
|
Width (mm)
|
Length (mm)
|
Zone Area (mm2)
|
|
1
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0
|
|
2
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0
|
Day # 4 -
Staphylococcus aureus
(ATCC 33591)
|
Zone of Inhibition
|
|
|
Trial # 1
|
Trial # 2
|
Average
|
|
Bandage
|
Width (mm)
|
Length (mm)
|
Width (mm)
|
Length (mm)
|
Width (mm)
|
Length (mm)
|
Zone Area (mm2)
|
|
1
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0
|
|
2
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0
|
Day # 5 -
Staphylococcus aureus
(ATCC 33591)
|
Zone of Inhibition
|
|
|
Trial # 1
|
Trial # 2
|
Average
|
|
Bandage
|
Width (mm)
|
Length (mm)
|
Width (mm)
|
Length (mm)
|
Width (mm)
|
Length (mm)
|
Zone Area (mm2)
|
|
1
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0
|
|
2
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0
|
Day # 6 -
Staphylococcus aureus
(ATCC 33591)
|
Zone of Inhibition
|
|
|
Trial # 1
|
Trial # 2
|
Average
|
|
Bandage
|
Width (mm)
|
Length (mm)
|
Width (mm)
|
Length (mm)
|
Width (mm)
|
Length (mm)
|
Zone Area (mm2)
|
|
1
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0
|
|
2
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0
|
Day # 7 -
Staphylococcus aureus
(ATCC 33591)
|
Zone of Inhibition
|
|
|
Trial # 1
|
Trial # 2
|
Average
|
|
Bandage
|
Width (mm)
|
Length (mm)
|
Width (mm)
|
Length (mm)
|
Width (mm)
|
Length (mm)
|
Zone Area (mm2)
|
|
1
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0
|
|
2
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0
|
|
Staphylococcus epidermidis
(ATCC 12228)
Day # 1 -
Staphylococcus epidermidis (ATCC 12228)
|
Zone of Inhibition
|
|
|
Trial # 1
|
Trial # 2
|
Average
|
|
Bandage
|
Width (mm)
|
Length (mm)
|
Width (mm)
|
Length (mm)
|
Width (mm)
|
Length (mm)
|
Zone Area (mm2)
|
|
1
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0
|
|
2
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0
|
Day # 2 -
Staphylococcus epidermidis (ATCC 12228)
|
Zone of Inhibition
|
|
|
Trial # 1
|
Trial # 2
|
Average
|
|
Bandage
|
Width (mm)
|
Length (mm)
|
Width (mm)
|
Length (mm)
|
Width (mm)
|
Length (mm)
|
Zone Area (mm2)
|
|
1
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0
|
|
2
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0
|
Day # 3 -
Staphylococcus epidermidis (ATCC 12228)
|
Zone of Inhibition
|
|
|
Trial # 1
|
Trial # 2
|
Average
|
|
Bandage
|
Width (mm)
|
Length (mm)
|
Width (mm)
|
Length (mm)
|
Width (mm)
|
Length (mm)
|
Zone Area (mm2)
|
|
1
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0
|
|
2
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0
|
Day # 4 -
Staphylococcus epidermidis (ATCC 12228)
|
Zone of Inhibition
|
|
|
Trial # 1
|
Trial # 2
|
Average
|
|
Bandage
|
Width (mm)
|
Length (mm)
|
Width (mm)
|
Length (mm)
|
Width (mm)
|
Length (mm)
|
Zone Area (mm2)
|
|
1
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0
|
|
2
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0
|
Day # 5 -
Staphylococcus epidermidis (ATCC 12228)
|
Zone of Inhibition
|
|
|
Trial # 1
|
Trial # 2
|
Average
|
|
Bandage
|
Width (mm)
|
Length (mm)
|
Width (mm)
|
Length (mm)
|
Width (mm)
|
Length (mm)
|
Zone Area (mm2)
|
|
1
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0
|
|
2
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0
|
Day # 6 -
Staphylococcus epidermidis (ATCC 12228)
|
Zone of Inhibition
|
|
|
Trial # 1
|
Trial # 2
|
Average
|
|
Bandage
|
Width (mm)
|
Length (mm)
|
Width (mm)
|
Length (mm)
|
Width (mm)
|
Length (mm)
|
Zone Area (mm2)
|
|
1
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0
|
|
2
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0
|
Day # 7 -
Staphylococcus epidermidis (ATCC 12228)
|
Zone of Inhibition
|
|
|
Trial # 1
|
Trial # 2
|
Average
|
|
Bandage
|
Width (mm)
|
Length (mm)
|
Width (mm)
|
Length (mm)
|
Width (mm)
|
Length (mm)
|
Zone Area (mm2)
|
|
1
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0
|
|
2
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0
|
Candida albicans
(ATCC 10231)
Day # 1 -
Candida albicans
(ATCC 10231)
|
Zone of Inhibition
|
|
|
Trial # 1
|
Trial # 2
|
Average
|
|
Bandage
|
Width (mm)
|
Length (mm)
|
Width (mm)
|
Length (mm)
|
Width (mm)
|
Length (mm)
|
Zone Area (mm2)
|
|
1
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0
|
|
2
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0
|
Day # 2 -
Candida albicans
(ATCC 10231)
|
Zone of Inhibition
|
|
|
Trial # 1
|
Trial # 2
|
Average
|
|
Bandage
|
Width (mm)
|
Length (mm)
|
Width (mm)
|
Length (mm)
|
Width (mm)
|
Length (mm)
|
Zone Area (mm2)
|
|
1
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0
|
|
2
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0
|
Day # 3 -
Candida albicans
(ATCC 10231)
|
Zone of Inhibition
|
|
|
Trial # 1
|
Trial # 2
|
Average
|
|
Bandage
|
Width (mm)
|
Length (mm)
|
Width (mm)
|
Length (mm)
|
Width (mm)
|
Length (mm)
|
Zone Area (mm2)
|
|
1
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0
|
|
2
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0
|
Day # 4 -
Candida albicans
(ATCC 10231)
|
Zone of Inhibition
|
|
|
Trial # 1
|
Trial # 2
|
Average
|
|
Bandage
|
Width (mm)
|
Length (mm)
|
Width (mm)
|
Length (mm)
|
Width (mm)
|
Length (mm)
|
Zone Area (mm2)
|
|
1
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0
|
|
2
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0
|
Day # 5 -
Candida albicans
(ATCC 10231)
|
Zone of Inhibition
|
|
|
Trial # 1
|
Trial # 2
|
Average
|
|
Bandage
|
Width (mm)
|
Length (mm)
|
Width (mm)
|
Length (mm)
|
Width (mm)
|
Length (mm)
|
Zone Area (mm2)
|
|
1
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0
|
|
2
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0
|
Day # 6 -
Candida albicans
(ATCC 10231)
|
Zone of Inhibition
|
|
|
Trial # 1
|
Trial # 2
|
Average
|
|
Bandage
|
Width (mm)
|
Length (mm)
|
Width (mm)
|
Length (mm)
|
Width (mm)
|
Length (mm)
|
Zone Area (mm2)
|
|
1
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0
|
|
2
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0
|
Day # 7 -
Candida albicans
(ATCC 10231)
|
Zone of Inhibition
|
|
|
Trial # 1
|
Trial # 2
|
Average
|
|
Bandage
|
Width (mm)
|
Length (mm)
|
Width (mm)
|
Length (mm)
|
Width (mm)
|
Length (mm)
|
Zone Area (mm2)
|
|
1
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0
|
|
2
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0
|
Summary:
Pseudomonas aeruginosa
(ATCC 9027)
|
Zone of Inhibition (mm2)
|
|
Bandage
|
Day 1
|
Day 2
|
Day 3
|
Day 4
|
Day 5
|
Day 6
|
Day 7
|
|
1
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
|
2
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
Staphylococcus aureus
(ATCC 33591)
|
Zone of Inhibition (mm2)
|
|
Bandage
|
Day 1
|
Day 2
|
Day 3
|
Day 4
|
Day 5
|
Day 6
|
Day 7
|
|
1
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
|
2
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
Staphylococcus epidermidis
(ATCC 12228)
|
Zone of Inhibition (mm2)
|
|
Bandage
|
Day 1
|
Day 2
|
Day 3
|
Day 4
|
Day 5
|
Day 6
|
Day 7
|
|
1
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
|
2
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
Candida albicans
(ATCC 10231)
|
Zone of Inhibition (mm2)
|
|
Bandage
|
Day 1
|
Day 2
|
Day 3
|
Day 4
|
Day 5
|
Day 6
|
Day 7
|
|
1
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
|
2
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
0.0
|
|
Conclusion: At the conclusion of the 7-day test, each bandage pad was removed from the corresponding culture plate and swabbed using a sterile cotton-swab stick. The cotton swabs used on the bandage strips from the Staphylococcus aureus (MRSA), Pseudomonas aeruginosa, and Staphylococcus epidermis culture plates were then placed in tryptic soy broth, while the cotton swab from the Candida albicans plate was placed in Sabourand Dextrose media. Observations of the presence of growth by noting the turbidity of the media for each bandage/strip combination are shown below:
|
Growth Tests after 7 day Kirby Bauer:
|
|
Pseudomonas
aeruginosa
|
Staphylococcus
aureus
|
Staphylococcus
epidermidis
|
Candida
albicans
|
|
Bandage
|
Trial #1
|
Trial #2
|
Trial #1
|
Trial #2
|
Trial #1
|
Trial #2
|
Trial #1
|
Trial #2
|
|
1
|
+++
|
+++
|
+++
|
+++
|
+++
|
+++
|
+++
|
+++
|
|
2
|
+++
|
+++
|
+++
|
+++
|
+++
|
+++
|
+++
|
+++
|
|
|
+++ Indicates Growth on Bandage Pad at Conclusion of Seven Day Test
--- Indicates No Growth on Bandage Pad at Conclusion of Seven Day Test
|
|
|
Construction of bandage: The underlying polymer surface is believed to be polyethylene based on FT-IR analysis and comparison to the Hummel Polymer Spectral library. The polyethylene is coated with metal through a vapor deposition process. The percentage of silver present, by weight, in each dressing was determined by taking a known weight of each material, dissolving it in concentrated nitric acid (Fisher, ACS Reagent Grade), diluting to 50 milliliters, and measuring the silver ion concentration using atomic absorption spectrometry as noted previously. Silver percentages of the dressings were then calculated.
The Curad package reports a wide range of 60-460 mg/m2 silver in the bandage. AA analysis performed here indicates that the bandages tested had 248 mg/m2. The percentage of the metal deposition is 4.29% by weight, of which 23.8% has been determined to be Ag, with the rest presumed to be aluminum as indicated by the packaging label.
|
Silver Release Tests:
Measurements. To determine the silver released from the subject dressings under static conditions, the pad of each dressing was placed in separate stoppered 250 mL Erlenmeyer flask containing 250 mL of Tryptic Soy Broth and stirred gently with a mechanical stirrer. Each flask was placed in a thermostated water bath at 298K. After 1, 2, 4, 8, 16, 24, 48, 72, 120, 192, and 288 hours, 1.0 mL of the broth was removed and placed in amber vials to which 50µL of 50% nitric acid was added as a preservative. The vials were stored at 278K to await analysis. At the end of the sample collection period, the samples were filtered through a 0.22µm syringe filter, and analyzed for silver ion concentration by flame atomic absorption using the 328.1 nm line of a Perkin-Elmer Lumina Ag Lamp in a Perkin-Elmer Aanalyst 300 Atomic Absorption Spectrometer. Each experiment was performed in duplicate.
|
|
1 hr
|
2 hr
|
4 hr
|
8 hr
|
24 hr
|
48 hr
|
|
Curad Silver Bandage
|
<1ppm
|
<1ppm
|
<1ppm
|
<1ppm
|
<1ppm
|
<1ppm
|
|
Curad Gel Bandage
|
<1ppm
|
<1ppm
|
<1ppm
|
<1ppm
|
<1ppm
|
<1ppm
|
|
