Technology and product reviews
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1. Two bacterial species (Pseudomonas aeruginosa and Staphylococcus aureus) were made into seeded agar plates and studied
2. After a four-hour incubation period, a silver- containing dressing was aseptically applied to the centre of the seeded-agar plate
3. There were marked differences in the adherence of fibroblasts to the silver- containing dressings tested
4. The wound surface contace layer (WSCL) of foam A was observed to have random and irregular shaped surface openings [Figure 6a], while foams B and C had regular,
uniformly distributed, equally sized and approximately 1mm diameter circular perforations in the adhesive
Dressing Bactericidal
HF-Ag AL-Ag Foam A Foam B Foam C
Notes: *The comments regarding bacteriostatic activity (eg stab culture of the seeded agar plate) are the result of visual observations of DEA plates (n=3 unless stated)
+The comments regarding bactericidal activity (eg stab culture of simulated colonised wound surface) are the result of visual observations of DEA plates (n=3 unless stated)
Table 3 – Bacteriostatic and bactericidal properties of the dressings tested.
percentage terms for the gelling dressings. The greatest relative (54%) and absolute reduction (25,166 cells/cm2
) in cell adherence
was observed for AL-Ag. However, the HF-Ag had the lowest adherence in both dry and hydrated states in this in vitro model.
Microscopy Light microscopy revealed that the HF-Ag dressing was composed of randomly oriented uniform fibres as previously described[6]
. The
surface of this dressing was difficult to define as it was not flat, smooth or regular. There were no observed differences between the sides (or faces). None of the dressing fibres were occluded, therefore all of the surface area (100%) would be available for absorption of fluids from a wound [Figures 2a and 3a]. The AL-Ag dressing had a similar physical
fibre-pad structure [Figure 2b]. However, at a higher magnification (x50) two different fibre types could be identified [Figure 2c]. One fibre was observed to be dark in colour (possibly the metallic silver-coated nylon fibres described by the manufacturer), while the other fibre was observed to be more translucent (possibly the gelling alginate fibre). The fibre pad of the AL-Ag dressing was wrapped in a thin ‘plastic sleeve’ perforated with regular and approximately oval holes. These holes were visibly observed in Figure 2b, are highlighted in Figure 2c, and were most clearly visible in the SEM image [Figure 3b]. The size (approximately 2.0mm maximum
43 Wounds International Vol 2 | Issue 4 | ©Wounds International 2011
x 1.3mm minimum) and area of these perforations was measured by image analysis and it was estimated that they constituted approximately 40% of the surface area of the dressing. The thin film of the sleeve was visually observed to be a barrier to liquid water (data not shown). The wound surface contact layer (WSCL)
of each foam dressing was observed to be a transparent and perforated layer which appeared to be well attached to the translucent bulk foam structure behind [Figures 4a, b and c]. The WSCLs of foams B and C were visually similar and regular, but that of foam A appeared to be somewhat different and more random in structure. Similarly, the foam components of foams B and C appeared visually to be similar but different from foam A. However, scanning electron micrographs of the three foams demonstrated that they shared many structural similarities and were observed to be composed of a series of interconnecting chambers [Figures 5a, b and c]. The WSCL of foam A was observed to
have random and irregular shaped surface openings [Figure 6a]. In comparison, foams B and C had regular, uniformly distributed, equally sized and approximately 1mm diameter circular perforations in the adhesive [Figures 6b and c]. An estimation of exposed accessible pores in foam A was <7%, whereas foams B and C gave areas of approximately 10%. The WSCL surfaces
P. aeruginosa Bacteriostatic
S. aureus
No effect detected
Bactericidal Bacteriostatic
No effect detected
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