Impact of Silver-Containing Wound Dressings on Bacterial Biofilm Viability and Susceptibility to Antibiotics during Prolonged Treatment

Abstract

The long-term antimicrobial efficacy of silver dressings against bacterial biofilms was investigated in a 7-day treatment in vitro model where the protein-rich medium was refreshed daily in order to mimic the conditions found in a wound bed. The use of plate-to-plate transfer assays demonstrated measurable differences in the effectivenesses of several silver dressings on the viability of biofilm bacteria and their susceptibility to antibiotics. Whereas after the first day of treatment, all dressings used resulted in a significant reduction in the number of viable cells in the biofilms and disruption of the biofilm colonies, during prolonged treatment, the efficacy of dressings with hydrophilic base materials diminished with daily transfers, and bacterial populations recovered. For dressings with hydrophobic base materials, the level of efficacy correlated with the silver species loaded. Biofilm bacteria, which survived the initial silver treatment, were susceptible to tobramycin, ciprofloxacin, and trimethoprim-sulfamethoxazole, in contrast to untreated biofilms, which were highly tolerant to the same antibiotics. This acquired susceptibility was unaffected by the longevity of pretreatment with the silver dressings but depended on the dressing used. The antimicrobial efficacy of the dressings correlated with the type of the dressing base material and silver species loaded.

Optimization and integration of nanosilver on polycaprolactone nanofibrous mesh for bacterial inhibition and wound healing in vitro and in vivo

“…As shown in Figure 6, extensive bacterial colonization produced by the proliferation of S. aureus, E. coli or A. baumannii was grouped on the surfaces of PCL, PCL/DA and PCL/NS0.5 films, and partial bacteria were encased in the polymeric matrix, which suggested the formation of biofilms. 43,44 In contrast, even though several bacteria could be observed on the surfaces of PCL/NS1.0 and PCL/NS2.0 films, no obvious polymeric matrix was found around the S. aureus, E. coli and A. baumannii bacteria, indicating that PCL/NS1.0 and PCL/NS2.0 could inhibit the formation of biofilms. Moreover, the area covered by the biofilms or bacteria on PCL/NS1.0 and PCL/NS2.0 surfaces were significantly smaller than that on the PCL, PCL/DA and PCL/NS0.5 surfaces.…”

Next Science Wound Gel Technology, a Novel Agent That Inhibits Biofilm Development by Gram-Positive and Gram-Negative Wound Pathogens

“…In comparison, NxtSc-G5 alone reduced the viability of 5 different wound pathogens by 6 to 8 log 10 CFU/disc in vitro and eliminated infections with these organisms in vivo. Furthermore, the effectiveness of silver dressings depends on the release of silver ions from the dressing and thus gradually decreases over time (29,51), whereas NxtSc-G5 was stable in vivo for up to 5 days. Therefore, NxtSc-G5 will likely maintain its effectiveness, although clinical studies are essential to corroborate our findings.…”

“…Systemic antimicrobials are added when the infection is deep and/or other infections are present (1)(2)(3)6). Numerous in vitro and clinical studies have evaluated the ability of topical antimicrobials to eliminate biofilms formed by wound pathogens, with variable efficacies being reported (27)(28)(29)(30)(31). Thus, there is a need for additional agents that not only can kill planktonic bacteria but also can disrupt biofilms and kill the bacteria within them.…”

Potential risks and benefits of nanotechnology: perceptions of risk in sunscreens

“…2006;Fernandez et al 2010a,b;MarambioJones and Hoek 2010;Su et al 2011). Ag-NPs have also been reported to have activity against bacterial biofilms (Kostenko et al 2010;Huang et al 2011). The bactericidal activity of Ag-NPs can be improved with combination with polymers such as chitosan and cationic polysaccharide (Banerjee et al 2010).…”

“…The antimicrobial activity of ionic silver, sustainability and decreased interference with dressings, decreased toxicity, and increased wound healing and fluid handling can be improved with combination with appropriate polymers (Maillard and Denyer 2006a,b). Kostenko et al (2010) and Toy and Macera (2011) review a number of commercially available ionic silver and Ag-NPs dressings.…”