Find your Coloplast country website

In vitro evaluation of Biatain® Silicone Ag and Biatain® Ag against biofilms and a broad range of microorganism


Clinically, implementation of biofilm based wound management has recently gained increasing attention4 and ideally, evaluation of antimicrobial wound dressings should include biofilm models aswell as standard antimicrobial tests. Biatain Silicone Ag and Biatain Ag were tested in two different in vitro test methods, a wound biofilm model and a standard antimicrobial test over time. As biofilms in non-healing wounds are heterogeneously distributed in the wound, including in the tissue below the wound bed 3, Biatain Silicone Ag and Biatain Agwere evaluated in an in vitro wound biofilm model that specifically addresses the problematic biofilms heterogeneously embedded in the wound environment. The study was published at EWMA 201820

Wound biofilm model

The aim of this test was to evaluate the efficacy of Biatain Silicone Ag and Biatain Ag against maturebiofilms and in the prevention of biofilm formation in a biofilm model simulating biofilms embedded inthe wound environment.


The in vitro wound biofilm model (WBM) is based on a study by S. Crone et al. and was developed at Costerton Biofilm Center, University of Copenhagen 30. The model consists of biofilm aggregates (either P. aeruginosa or S. aureus) embedded and grown in semi-solid agar. S. aureus and P. aeruginosa are both keen biofilm formers and will form mature biofilms within 24 hours in vitro. The microorganisms were inoculated into the semi-solid agar containing nutrients and either grown to mature biofilms for 24 hours or treated shortly after inoculation to demonstrate biofilm prevention. In both test setups, the microorganisms/biofilms were subsequently exposed for 24 hours to samples of Biatain Silicone Ag,Biatain Ag or control dressings without silver (Figure 1).

Model drawing of the WBM illustrating biofilms embedded in the agar. 

Figure 1


Both Biatain® Silicone Ag and Biatain Ag showed statistically significant effect against mature biofilmsof S. aureus and P. aeruginosa, compared to control dressings without silver (Figure 2A & B). Both testdressings reduced mature P. aeruginosa biofilms by more than 99.99% and mature S. aureus biofilmsby 99.3% (Biatain Silicone Ag) and 99.93% (Biatain Ag), (p<0.001 vs. control for all, Students T-test).The variation in results between different bacterial strains is expected and caused by the differences insusceptibility of microorganisms to silver.

Killing of mature biofilms tested in the WBM. 

The results are shown as geometrical mean of CFU/ml ± standard deviation (SD). N=20 samples. The horizontal line represents limit of detection at 25 CFU/ml (CFU=Colony Forming Unit).

Figure 2

Biatain Silicone Ag and Biatain Ag equally prevented growth of biofilms of S. aureus and P. aeruginosa (p<0.001 vs. control for all, Students T-test) to the limit of detection which was set to 25 CFU/m l (Figure 3A & B).

Prevention of biofilm formation tested in the WBM. 

The results are shown as geometricalmean of CFU/ml ± SD. N=20 samples. The horizontal line represents limit of detection at 25 CFU/ml.

Figure 3


Biatain® Silicone Ag and Biatain Ag were effective against mature biofilms and in prevention of biofilm formation. Both treatment of mature biofilms and prevention of biofilm formation are essential strategies in the framework for the treatment of wounds with biofilms 4. The differences in the efficacy against mature S. aureus and P. aeruginosa biofilms were expected and most likely caused by differences in susceptibility of the two microorganisms to silver. A generally accepted explanation to this, is the structural differences in the cell walls of Gram-positive and Gram-negative bacteria. Gram positive bacteria such as S. aureus have thicker cell walls that are more difficult for silver ions to penetrate31,32. Additionally, microbiological variation also cause some variation in test results, e.g. as the difference seen for S. aureus and the two tested products.

Standard antimicrobial testing over 7 days

The “Standard test method for determining the antimicrobial activity of antimicrobial agents under dynamic contact conditions”, ASTM E2149-13a31 enables a simple, standard evaluation of antimicrobial wound dressings against a wide range of pathogenic microorganisms normally found in non-healing wounds at time points representing relevant wear times.

Method description

Tests of Biatain Silicone Ag and Biatain Ag were performed over a 7-day period. Dressing samples were submerged in separate Erlenmeyer flasks containing a microbial monoculture with a starting concentration of 105-106 CFU/ml. The samples were incubated for 24 hours and then moved to newflasks, every day for 7 days. This challenges the samples as it is repeatedly exposed to excessive liquid containing high concentration of microorganisms (Figure 4).

Illustration of the E2149-13a test methods. 

Figure 4

The antimicrobial activity was evaluated based on the log reduction results. The current log reduction requirements for antimicrobial wound dressings is defined as a log 3 reduction compared with the start concentration of microorganisms (prEN16756)34

Six microorganisms were tested in the model, representing some of the most prevalent and pathogenic microorganisms found in infected wounds35,37, including antibiotic resistant bacteria, and broadly covering the microbial differences between Gram-positive bacteria, Gram-negative bacteria and fungi:

• Staphylococcus aureus (Gram-positive bacteria)

• Pseudomonas aeruginosa (Gram-negative bacteria)

• Methicillin-resistant Staphylococcus aureus (MRSA) (Gram-positive bacteria)

• Vancomycin-resistant Enterococci (VRE) (Gram-positive bacteria)

• Candida albicans (yeast)

• Aspergillus brasiliensis (mold)



Both dressings reduced all six tested microorganisms, including the antibiotic resistant strains, by morethan log 3. The antimicrobial activity was similar on day 1 and 7 (Figure 5 A & B) indicating asustained and effective release of silver up to 7 days. The variation in results between differentmicroorganisms is expected and caused by the differences in susceptibility of microorganisms to silverand general microbiological variation.

Antimicrobial efficacy tested according to ASTM E2149-13a against a broad range of microorganisms. 

Figure 5


The ASTM E2149-13a test provides information about antimicrobial efficacy of a wound dressingagainst a broad range of planktonic microorganisms over time. The antimicrobial efficacy of both Biatain® Silicone Ag and Biatain Ag was sustained for 7 days with the daily challenge of new freshlycultured microorganisms.


The test represents a worst-case scenario. In non-healing wounds, new microorganisms would not besupplied every day and the amount of released silver would accumulate in the wound bed, resulting ina higher concentration of silver over time and a potentially greater antimicrobial effect than in the invitro situation. On the other hand, this standard test does not consider the presence and complexity ofmicrobial biofilms and only provides information about the basic antimicrobial activity. Therefore, thetest results should not be the sole basis for an antimicrobial product evaluation.


Conclusion on in vitro tests

Biatain Silicone Ag and Biatain Ag dressings are modern wound dressings containing the antimicrobial agent silver with an intended use for infected wounds and wounds at risk of infection. Biatain Silicone Agand Biatain Ag demonstrated antimicrobial efficacy against a wide range of pathogenic microorganisms commonly found in non-healing and infected wounds. The antimicrobial effect was continuous for 7 days with daily challenge of freshly cultured microorganisms. Biatain Silicone Ag and Biatain Ag also demonstrated statistically significant efficacy against mature biofilms of both S. aureus and P. aeruginosa, and in prevention of biofilm formation in an embedded wound biofilm model. Both treatment of mature biofilms and prevention of biofilm formation are essential strategies in the framework for the treatment of wound infection 4

Reference list

See full list of references

1. International Wound Infection Institute (IWII). Wound infection in clinical practice. Wounds International. 2016.

2. Coloplast A/S, ReD associates. Data on file. 2014.

3. Schultz G, Bjarnsholt T, James GA, Leaper DJ, McBain AJ, Malone M, et al. Consensus guidelines for the identification and treatment ofbiofilms in chronic nonhealing wounds. Wound Repair and Regeneration. 2017;25(5):744-57.

4. World Union of Wound Healing Societies (WUWHS). Florence Congress, Position Document. Management of biofilm. 2016.

5. Appropriate use of silver dressings in wounds. An expert working group consensus. International consensus. London; 2012.

6. Lansdown AB. A review of the use of silver in wound care: facts and fallacies. British Journal of Nursing. 2004;13(6):s6-19.

7. Rodriguez-Arguello J, Lienhard K, Patel P, Geransar R, Somayaji R, Parsons L, et al. A Scoping Review of the Use of Silver-impregnatedDressings for the Treatment of Chronic Wounds. Ostomy Wound Management. 2018;64(3):14-31.

8. Dissemond J, Bottrich JG, Braunwarth H, Hilt J, Wilken P, Munter KC. Evidence for silver in wound care - meta-analysis of clinical studiesfrom 2000-2015. Journal of the German Society of Dermatology. 2017;15(5):524-35.

9. Norman G, Westby MJ, Rithalia AD, Stubbs N, Soares MO, Dumville JC. Dressings and topical agents for treating venous leg ulcers.Cochrane Database of Systematic Reviews. 2018(6):1-289.

10. Münter KC, Beele H, Russell L, Crespi A, Grochenig E, Basse P, et al. Effect of a sustained silver-releasing dressing on ulcers with delayedhealing: the CONTOP study. Journal of wound care. 2006;15(5):199-206.

11. Jørgensen B, Price P, Andersen KE, Gottrup F, Bech-Thomsen N, Scanlon E, et al. The silver-releasing foam dressing, Contreet Foam,promotes faster healing of critically colonised venous leg ulcers: a randomised, controlled trial. International wound journal. 2005;2(1):64-73.

12. Rayman G, Rayman A, Baker NR, Jurgeviciene N, Dargis V, Sulcaite R, et al. Sustained silver-releasing dressing in the treatment of diabeticfoot ulcers British Journal of Nursing. 2004;14(2);109-14.

13. Humbert P, Zuccarelli F, Debure C, Vendeaud Busquet F, Bressieux J-M, Bedane C, et al. Leg Ulcers Presenting Local Signs of Infection:Interest of Biatain Argent Wound Dressing. Journal des Plaies et Cicatrisations. 2006;52(9):41-7.

14. Lázaro-Martínez JL, Álvaro-Afonso FJ, García-Álvarez Y, García-Morales E, Sanz-Corbalán I, Molines-Barroso RJ. Clinical and microbiologicaleffectiveness of a hydropolymer alveolar dressing with ionic silver complex and silicone adhesive. Poster, EWMA(EPP021); 2018.

15. Leaper D, Münter C, Meaume S, Scalise A, Mompó NB, Jakobsen BP, et al. The Use of Biatain Ag in Hard-to-Heal Venous Leg Ulcers:Meta-Analysis of Randomised Controlled Trials. PLoS ONE. 2013;8(7):e67083.

16. Jemec GB, Kerihuel JC, Ousey K, Lauemoller SL, Leaper DJ. Cost-Effective Use of Silver Dressings for the Treatment of Hard-to-HealChronic Venous Leg Ulcers. Plos One. 2014;9(6):e100582.

17. Mouës C, Heule F, Legerstee R, Hovius S. Five Millennia of Wound Care Products - What is New? A Literature Review. Ostomy WoundManagement. 2009;55(3):16-8.

18. Sibbald R, Williamson D, Orsted H, Campbell K, Keast D, Krasner D, et al. Preparing the Wound Bed - Debridement, Bacterial Balance, andMoisture Balance. Ostomy Wound Management. 2000;46(11):14-35.

19. Adderley UJ. Managing wound exudate and promoting healing. British Journal of Community Nursing. 2010;15(3):15-20.

20. Christiansen C, Huniche GB, Allesen-Holm M. In vitro evaluation of a silver foam dressing with and without silicone adhesive againstbiofilms and a broad range of microorganisms. Poster, EWMA(EPP025); 2018.

21. Lansdown AB. Silver in health care: antimicrobial effects and safety in use. Current Problems in Dermatology. 2006;33:17-34.

22. Percival SL, Thomas J, Linton S, Okel T, Corum L, Slone W. The antimicrobial efficacy of silver on antibiotic-resistant bacteria isolated fromburn wounds. International wound journal. 2012;9(5):488-93.

23. Böttrich JG, Brill FHH, Dissemond J, Steinmann J, Münter KC, Schümmelfeder F, et al. A Systematic Review of the Risk of BacterialResistance to Silver. Poster, EWMA; 2018.

24. Percival SL, Woods E, Nutekpor M, Bowler P, Radford A, Cochrane C. Prevalence of Silver Resistance in Bacteria Isolated from DiabeticFoot Ulcers and Efficacy of Silver-Containing Wound Dressings. Ostomy Wound Management. 2008;54(3):30-40.

25. Kostenko V, Lyczak J, Turner K, Martinuzzi RJ. Impact of Silver-Containing Wound Dressings on Bacterial Biofilm Viability and Susceptibilityto Antibiotics during Prolonged Treatment. Antimicrobial Agents and Chemotherapy. 2010;54(12):5120-31.

26. Burger C, Lemoult S, Andersen MB. Silver release profile and antibacterial effect of a new silver foam dressing with silicone adhesive.Poster, EWMA(EPP025); 2018.

27. Malone M, Bjarnsholt T, McBain AJ, James GA, Stoodley P, Leaper D, et al. The prevalence of biofilms in chronic wounds: a systematicreview and meta-analysis of published data. Journal of wound care. 2017;26(1):20-5.

28. Bjarnsholt T. The Role of Bacterial Biofilms in Chronic Infections. Acta pathologica, microbiologica, et immunologica Scandinavica.2013;121(s136):1-58.

29. Costerton JW. Bacterial Biofilms: A Common Cause of Persistent Infections. Science. 1999;284(5418):1318-22.

30. Crone S, Garde C, Bjarnsholt T, Alhede M. A novel in vitro wound biofilm model used to evaluate low-frequency ultrasonic-assisted wounddebridement. Journal of wound care. 2015;24(2):64-72.

31. Bessa LJ, Fazii P, Di Giulio M, Cellini L. Bacterial isolates from infected wounds and their antibiotic susceptibility pattern: some remarksabout wound infection. International wound journal. 2013;12(1):47-52.

32. Yin HQ, Langford R, Burrell RE. Comparative Evaluation of the Antimicrobial Activity of ACTICOAT Antimicrobial Barrier Dressing. Journalof Burn Care & Rehabilitation. 1999;20(3):195-200.

33. ASTM E2149-13a, Standard Test Method for Determining the Antimicrobial Activity of Antimicrobial Agents Under Dynamic ContactConditions. ASTM International. 2013.

34. prEN16756 (draft). Antimicrobial wound dressings – Requirements and test methods. 2014.

35. Howell-Jones RS, Wilson MJ, Hill KE, Howard AJ, Price PE, Thomas DW. A review of the microbiology, antibiotic usage and resistance inchronic skin wounds. Journal of Antimicrobial Chemotherapy. 2005;55(2):143-9.

36. Bowler PG, Duerden BI, Armstrong DG. Wound Microbiology and Associated Approaches to Wound Management. Clinical MicrobiologyReviews. 2001;14(2):244-69.

37. Daeschlein G. Antimicrobial and antiseptic strategies in wound management. International wound journal. 2013;10 Suppl 1:9-14.

38. Thomas S. Laboratory findings on the exudate-handling capabilities of cavity foam and foam-film dressings. Journal of wound care.2010;19(5):192-9.

39. White R, Cutting KF. Modern exudate management: a review of wound treatments. Poster, EWMA(EPP025); 2018.

40. Romanelli M, Vowden K, Weir D. Exudate management made easy. Wounds International. 2010;1(2):1-6.

41. Andersen MB. Comparison of 24 hours fluid handling and absorption under pressure between four wound dressings with Ag and siliconeadhesive. EWMA(EP296); 2016.

42. Baños AM, Nogueras FI, Palomar LF. Clinical evaluation of a silver dressing in the treatment of infected and colonized ulcers. Revista deenfermería. 2008;31(3):42-8.

43. Senet P, Bause R, Jorgensen B, Fogh K. Clinical efficacy of a silver-releasing foam dressing in venous leg ulcer healing: a randomisedcontrolled trial. International wound journal. 2014;11(6):649-55.

44. Flanagan M. Wound measurement: can it help us to monitor progression to healing? Journal of wound care. 2003;12(5):189-94.

View desktop version