A laboratory study tested a carboxymethyl cellulose (CMC) burn dressing containing 1.2% ionic silver for its antimicrobial efficacy and silver availability over 21 days against Staphylococcus aureus and Pseudomonas aeruginosa in a simulated wound fluid model. The silver CMC dressing rapidly reduced high populations of both bacteria throughout testing and maintained silver availability even after dehydration and rehydration, showing promise for treating partial thickness burns for up to 21 days.

1. A laboratory study was undertaken to investigate the availability and anti-
microbial efficacy of silver within a carboxymethyl cellulose (CMC) dress-
ing for the management of partial thickness burns (PTB). The intended use
of the burn dressing is for it to be applied to a clean PTB wound and left in
place until the wound has reepithelialised up to a maximum of 21 days. It
is therefore important for the silver content to remain effective throughout
this period. The burn dressing is made up of a non-woven CMC fabric with
nylon stitchbonding and contains 1.2 % ionic silver (Figure 1).
Figure 1. Silver CMC Burn Dressing
Antimicrobial Efficacy:
An in vitro simulated wound fluid model was used to evaluate the anti-
microbial activity of the silver CMC burn dressing against Staphylo-
coccus aureus and Pseudomonas aeruginosa, 3 replicates were test-
ed per challenge organism. Dressing samples were incubated with
the challenge organism (~1 x 106
cfu/ mL) for 21 days, with re-inocula-
tion of the challenge organism at days 4, 9 and 17 (at least 1x105
cfu)
labelled R1, R2 and R3, to simulate wound conditions. The equivalent
CMC burn dressings without silver were used as the negative control.
The in vitro simulated wound fluid model data show that the
silver CMC burn dressing rapidly and repeatedly reduced
high populations of the challenge organisms throughout
the test period of 21 days. Silver availability testing shows
that silver is available throughout the test period and that
availability is not adversely affected by dehydration and
subsequent re-hydration of the dressing material.
Silver CMC burn dressing is AQUACEL®
Ag BURN Dressing, CMC Dressing is AQUACEL®
Dressing
®/ ™ indicated a trademark of ConvaTec Inc.
©2013 ConvaTec Inc. AP-013566-MM
In Vitro Studies on a Silver CMC Burn Dressing
Lucy Ballamy, Victoria Towers, Darryl Short and Sarah Welsby
Antimicrobial Efficacy:
The silver CMC burn dressing was efficacious against both S. aureus and P.
aeruginosa in the simulated wound fluid model over 21 days, as shown in Figure
2.
Figure 2. Antimicrobial Efficacy
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Timepoint (Days)
SilverAvailability(ppm)
Silver Availability Analysis:
The availability of silver from the silver CMC burn dressing was analysed by im-
mersing dressing samples in 0.9 % w/v sodium chloride (saline solution) over a
28 day period at 37O
C with stirring. Aliquots of the solution were taken after 7, 11,
18, 25 and 28 days and tested for silver using a Perkin Elmer AAnalyst Atomic
Absorption Spectrophotometer. At days 7 and 18 the dressing samples were re-
moved from the saline solution and dried out for 24 hours before being replaced
into fresh saline which created a further challenge and was designed to mimic
a burn wound drying out and then being rehydrated with saline. The experiment
was carried out in triplicate.
Figure 3. Silver Availability Analysis
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Silver CMC Burn Dressing vs S. aureus (n=3) CMC Dressing vs S. aureus (negative control, n=3)
Silver CMC Burn Dressing vs P. aeruginosa (n=3) CMC Dressing vs P. aeruginosa (negative control, n=3)
R1
R2
R3
TotalViableCounts(Log10cfu/mL)
Timepoint (Days)
Silver Availability Analysis:
The silver availability test showed the silver content of the silver CMC dress-
ing at 28 days was comparable to that after 7 days as shown in Figure 3.