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An in vitro comparison of two silver-containing antimicrobial wound dressings
Samuel J Hooper1, David W Williams, David W Thomas
1Cardiff University Dental Hospital, Wales, UK.
Abstract:
Preclinical studies have shown that release of silver by different wound dressings varies. The purpose of this in vitro study was to compare the antimicrobial activity of silver alginate (SA) and silver carboxymethylcellulose (SCM) dressings. An- timicrobial activity was tested using nine bacterial strains with log10 reduction and corrected zone of inhibition (CZOI) as- says. Antimicrobial effect was visualized using confocal microscopy (CLSM). Log10 reduction was comparable between both dressings for Staphylococcus aureus NCIMB 9518, Candida albicans ATCC 90028, Finegoldia magna NCTC 11804T, and Pseudomonas aeruginosa NCTC 10662. Log10 reduction was higher for SCM than SA dressing-exposed Escherichia coli (P = 0.035) and P. aeruginosa ATCC 15692 (P = 0.032), and lower for SCM than SA dressing-exposed Streptococcus pyogenes (P = 0.007), Peptoniphilus asaccharolyticus (P = 0.045), and S. aureus NCTC 8325 (P = 0.012). Both dressings were equivalent against four strains (5 to 8 days' activity) in the CZOI assay. SA dressing silver activity lasted >24 hours longer than SCM activity when exposed to C. albicans (9 days' activity), E. coli (7 days' activity), F. magna (5 days' activity), and P. asaccharolyticus (5 days' activity), whereas the SMC exhibited greater persistence against S. pyogenes (13 days' activity). CLSM showed complete kill of S. aureus after 20 hours for both dressings. The results of this study confirm the broad-spectrum, in vitro activity of some dressings containing ionic silver. The in vitro antimicrobial efficacy of both wound dressings was comparable, but clinical studies comparing the efficacy and effectiveness of silver-containing dressings to nonionic silver-containing dressings are needed.
Insights
This study compared silver alginate (SA) and silver carboxymethylcellulose (SCM) wound dressings. Both dressings showed comparable in vitro antimicrobial activity, though differences were noted against specific bacterial strains and in silver ion release duration.
Area of Science:
- Wound healing and biomaterials science
- Antimicrobial efficacy testing
- In vitro microbiology
Background:
- Silver-containing wound dressings are utilized for their antimicrobial properties.
- The release kinetics and efficacy of silver ions can vary significantly between different dressing formulations.
- Understanding the comparative antimicrobial activity of various silver dressings is crucial for optimizing wound care.
Purpose of the Study:
- To compare the in vitro antimicrobial activity of silver alginate (SA) and silver carboxymethylcellulose (SCM) wound dressings.
- To evaluate the duration of antimicrobial effect and silver ion release for both SA and SCM dressings.
- To assess the efficacy against a panel of relevant bacterial and fungal strains.
Main Methods:
- In vitro testing of antimicrobial activity using log10 reduction assays.
- Determination of corrected zone of inhibition (CZOI) to assess the duration of antimicrobial effect.
- Confocal laser scanning microscopy (CLSM) for visualization of antimicrobial effects.
- Testing against nine different bacterial and fungal strains.
Main Results:
- Log10 reduction was comparable between SA and SCM for four strains, but SCM showed higher activity against E. coli and P. aeruginosa ATCC 15692, while SA was more effective against S. pyogenes, P. asaccharolyticus, and S. aureus NCTC 8325.
- Both dressings demonstrated equivalent antimicrobial activity duration against four strains in the CZOI assay (5-8 days).
- SA dressing exhibited longer silver activity than SCM against C. albicans, E. coli, F. magna, and P. asaccharolyticus, whereas SCM showed greater persistence against S. pyogenes.
Conclusions:
- Both silver alginate and silver carboxymethylcellulose dressings exhibit broad-spectrum in vitro antimicrobial activity.
- The antimicrobial efficacy of the two dressings is largely comparable, with specific differences in activity against certain microorganisms and duration of effect.
- Further clinical studies are needed to compare the efficacy of ionic silver dressings with non-ionic silver formulations in real-world wound management scenarios.
