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In vitro assessment of the antimicrobial activity of wound dressings: influence of the test method selected and impact of the pH.

Wiegand C, Abel M, Ruth P, Elsner P, Hipler UC - J Mater Sci Mater Med (2015)

Bottom Line: They did not exhibit any antimicrobial effects in the ADT, MLN or LQbATP, since these methods depend on diffusion/extraction of an active agent.However, they showed a strong antimicrobial effect in the challenge tests as they possess a high absorptive capacity, and are able to bind and sequester micro-organisms present.Therefore, it seems recommendable to choose several tests to distinguish whether a material conveys an active effect or a passive mechanism.

View Article: PubMed Central - PubMed

Affiliation: Department of Dermatology, University Hospital Center Jena, Erfurter Str. 35, 07740, Jena, Germany, C.Wiegand@med.uni-jena.de.

ABSTRACT
Antibacterial activity of dressings containing antimicrobials is mostly evaluated using in vitro tests. However, the various methods available differ significantly in their properties and results obtained are influenced by the method selected, micro-organisms used, and extraction method, the degree of solubility or the diffusability of the test-compounds. Here, results on antimicrobial activity of silver-containing dressings obtained by agar diffusion test (ADT), challenge tests (JIS L 1902, AATCC 100), and extraction-based methods (microplate laser nephelometry (MLN), luminescent quantification of bacterial ATP (LQbATP)) using Staphylococcus aureus and Pseudomonas aeruginosa were evaluated. Furthermore, the effect of the pH on antibacterial efficacy of these dressings was investigated. All silver-containing dressings exerted antimicrobial activity in all in vitro tests and results correlated considerably well. Differences were observed testing the agent-free basic materials. They did not exhibit any antimicrobial effects in the ADT, MLN or LQbATP, since these methods depend on diffusion/extraction of an active agent. However, they showed a strong antimicrobial effect in the challenge tests as they possess a high absorptive capacity, and are able to bind and sequester micro-organisms present. Therefore, it seems recommendable to choose several tests to distinguish whether a material conveys an active effect or a passive mechanism. In addition, it could be shown that release of silver and its antimicrobial efficacy is partially pH-dependent, and that dressings themselves affect the pH. It can further be speculated that dressings' effects on pH and release of silver ions act synergistically for antimicrobial efficacy.

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Related in: MedlinePlus

For the ADT, MH2 agar plates were inoculated with S. aureus or P. aeruginosa and incubated with the wound dressing samples at 37 °C for 24 h. Afterwards, the zone of inhibition (ZOI) was measured. Pictures show the photographic documentation of representative ADT results
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Fig1: For the ADT, MH2 agar plates were inoculated with S. aureus or P. aeruginosa and incubated with the wound dressing samples at 37 °C for 24 h. Afterwards, the zone of inhibition (ZOI) was measured. Pictures show the photographic documentation of representative ADT results

Mentions: Dressings without active agent, such as alginate, CMC and PU-foam with TLC, had no effect in the ADT (Fig. 1). On the other hand, the silver-containing dressings, alginate + ionic-Ag, alginate + nano-Ag and CMC with Ag+, exhibited a formation of a distinct zone of inhibition (ZOI) for both, S. aureus and P. aeruginosa. It was further noted that the effect on S. aureus was slightly higher compared to P. aeruginosa. In contrast, for PU-foam with TLC/Ag+ inhibition of bacterial growth was only found directly under the sample and no ZOI was formed.Fig. 1


In vitro assessment of the antimicrobial activity of wound dressings: influence of the test method selected and impact of the pH.

Wiegand C, Abel M, Ruth P, Elsner P, Hipler UC - J Mater Sci Mater Med (2015)

For the ADT, MH2 agar plates were inoculated with S. aureus or P. aeruginosa and incubated with the wound dressing samples at 37 °C for 24 h. Afterwards, the zone of inhibition (ZOI) was measured. Pictures show the photographic documentation of representative ADT results
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4325976&req=5

Fig1: For the ADT, MH2 agar plates were inoculated with S. aureus or P. aeruginosa and incubated with the wound dressing samples at 37 °C for 24 h. Afterwards, the zone of inhibition (ZOI) was measured. Pictures show the photographic documentation of representative ADT results
Mentions: Dressings without active agent, such as alginate, CMC and PU-foam with TLC, had no effect in the ADT (Fig. 1). On the other hand, the silver-containing dressings, alginate + ionic-Ag, alginate + nano-Ag and CMC with Ag+, exhibited a formation of a distinct zone of inhibition (ZOI) for both, S. aureus and P. aeruginosa. It was further noted that the effect on S. aureus was slightly higher compared to P. aeruginosa. In contrast, for PU-foam with TLC/Ag+ inhibition of bacterial growth was only found directly under the sample and no ZOI was formed.Fig. 1

Bottom Line: They did not exhibit any antimicrobial effects in the ADT, MLN or LQbATP, since these methods depend on diffusion/extraction of an active agent.However, they showed a strong antimicrobial effect in the challenge tests as they possess a high absorptive capacity, and are able to bind and sequester micro-organisms present.Therefore, it seems recommendable to choose several tests to distinguish whether a material conveys an active effect or a passive mechanism.

View Article: PubMed Central - PubMed

Affiliation: Department of Dermatology, University Hospital Center Jena, Erfurter Str. 35, 07740, Jena, Germany, C.Wiegand@med.uni-jena.de.

ABSTRACT
Antibacterial activity of dressings containing antimicrobials is mostly evaluated using in vitro tests. However, the various methods available differ significantly in their properties and results obtained are influenced by the method selected, micro-organisms used, and extraction method, the degree of solubility or the diffusability of the test-compounds. Here, results on antimicrobial activity of silver-containing dressings obtained by agar diffusion test (ADT), challenge tests (JIS L 1902, AATCC 100), and extraction-based methods (microplate laser nephelometry (MLN), luminescent quantification of bacterial ATP (LQbATP)) using Staphylococcus aureus and Pseudomonas aeruginosa were evaluated. Furthermore, the effect of the pH on antibacterial efficacy of these dressings was investigated. All silver-containing dressings exerted antimicrobial activity in all in vitro tests and results correlated considerably well. Differences were observed testing the agent-free basic materials. They did not exhibit any antimicrobial effects in the ADT, MLN or LQbATP, since these methods depend on diffusion/extraction of an active agent. However, they showed a strong antimicrobial effect in the challenge tests as they possess a high absorptive capacity, and are able to bind and sequester micro-organisms present. Therefore, it seems recommendable to choose several tests to distinguish whether a material conveys an active effect or a passive mechanism. In addition, it could be shown that release of silver and its antimicrobial efficacy is partially pH-dependent, and that dressings themselves affect the pH. It can further be speculated that dressings' effects on pH and release of silver ions act synergistically for antimicrobial efficacy.

Show MeSH
Related in: MedlinePlus