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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 evaluation of the MLN and LQbATP assay results, data was transformed to read the growth of S. aureus (a) and P. aeruginosa (b) in [%] compared to the medium control. It was found that the basic materials alginate, CMC, and PU-foam with TLC did not significantly affect bacterial growth. Extracts of alginate + ionic-Ag and alginate + nano-Ag demonstrated a complete reduction of S. aureus and P. auruginosa. Differing results were found for the extracts of CMC with Ag+ and PU-foam with TLC/Ag+. Here, the LQbATP did not show an equal reduction of microbial growth compared to MLN where inhibition of bacterial growth was clearly observable
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Fig3: For evaluation of the MLN and LQbATP assay results, data was transformed to read the growth of S. aureus (a) and P. aeruginosa (b) in [%] compared to the medium control. It was found that the basic materials alginate, CMC, and PU-foam with TLC did not significantly affect bacterial growth. Extracts of alginate + ionic-Ag and alginate + nano-Ag demonstrated a complete reduction of S. aureus and P. auruginosa. Differing results were found for the extracts of CMC with Ag+ and PU-foam with TLC/Ag+. Here, the LQbATP did not show an equal reduction of microbial growth compared to MLN where inhibition of bacterial growth was clearly observable

Mentions: Using LQbATP, similar results were obtained in regard to the basic materials that did not significantly affect bacterial growth (Fig. 3). Moreover, extracts of alginate + ionic-Ag and alginate + nano-Ag also demonstrated a complete reduction of S. aureus and P. auruginosa. However, differing results were found for the extracts of CMC with Ag+ and PU-foam with TLC/Ag+ against both, S. aureus (Fig. 3a) and P. aeruginosa (Fig. 3b). Here, the LQbATP did not show an equal reduction of microbial growth compared to the MLN where the inhibition of bacterial growth was clearly observable.Fig. 3


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 evaluation of the MLN and LQbATP assay results, data was transformed to read the growth of S. aureus (a) and P. aeruginosa (b) in [%] compared to the medium control. It was found that the basic materials alginate, CMC, and PU-foam with TLC did not significantly affect bacterial growth. Extracts of alginate + ionic-Ag and alginate + nano-Ag demonstrated a complete reduction of S. aureus and P. auruginosa. Differing results were found for the extracts of CMC with Ag+ and PU-foam with TLC/Ag+. Here, the LQbATP did not show an equal reduction of microbial growth compared to MLN where inhibition of bacterial growth was clearly observable
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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

Fig3: For evaluation of the MLN and LQbATP assay results, data was transformed to read the growth of S. aureus (a) and P. aeruginosa (b) in [%] compared to the medium control. It was found that the basic materials alginate, CMC, and PU-foam with TLC did not significantly affect bacterial growth. Extracts of alginate + ionic-Ag and alginate + nano-Ag demonstrated a complete reduction of S. aureus and P. auruginosa. Differing results were found for the extracts of CMC with Ag+ and PU-foam with TLC/Ag+. Here, the LQbATP did not show an equal reduction of microbial growth compared to MLN where inhibition of bacterial growth was clearly observable
Mentions: Using LQbATP, similar results were obtained in regard to the basic materials that did not significantly affect bacterial growth (Fig. 3). Moreover, extracts of alginate + ionic-Ag and alginate + nano-Ag also demonstrated a complete reduction of S. aureus and P. auruginosa. However, differing results were found for the extracts of CMC with Ag+ and PU-foam with TLC/Ag+ against both, S. aureus (Fig. 3a) and P. aeruginosa (Fig. 3b). Here, the LQbATP did not show an equal reduction of microbial growth compared to the MLN where the inhibition of bacterial growth was clearly observable.Fig. 3

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