An In Vitro Analysis of the Antimicrobial Activity of a Silver Containing Collagen Dressing over Seven Days

Aim: Collagen dressings are often used in the treatment of recalcitrant wounds due to their ability to act as a sacrificial substrate for proteases while maintaining a moist wound environment. The addition of silver to collagen dressings may be useful in preventing dressing colonization and potential wound infection. The antimicrobial activity of a novel collagen-biopolymer dressing composed of collagen, carboxymethylcellulose (CMC), alginate, ethylenediaminetetraacetic acid (EDTA) and silver was assessed in vitro through a 7-day Kirby-Bauer assay against five common wound pathogens.

Method: Samples of collagen-biopolymer dressing with silver were transferred daily to fresh Mueller Hinton Agar plates inoculated with methicillin-resistant Staphylococcus aureus (MRSA), Pseudomonas aeruginosa, Escherchia coli, vancomycin-resistant Enterococcus faecalis (VRE), or Candida albicans. The zone of inhibition (ZOI) was calculated by subtracting the sample width from the diameter of the clear zone (in mm).

Results/Discussion: The collagen-biopolymer dressing with silver produced a ZOI on each day of the 7-day study against all of the microorganisms tested. The largest ZOIs were observed for MRSA (18-21 mm) and C. albicans (8-10 mm). Smaller ZOIs were consistently recorded for E. coli (1-3 mm), P. aeruginosa (2-4 mm), and VRE (1-3 mm).

Conclusion: The collagen, EDTA, CMC, alginate and silver dressings demonstrated sustained antimicrobial activity in a 7-day Kirby-Bauer challenge with MRSA, P. aeruginosa, E. coli, VRE, and C. albicans, indicating its ability to protect the wound from external contamination while aiding in the epithelialization of the wound bed through binding of excess MMPs and maintenance of a moist wound environment.