Cadexomer Iodine - disruption of a variety of micro-organisms grown in pre-established single and mixed species biofilms

Objectives: The simplistic definition of a biofilm is a structured community of bacterial cells enclosed in a self-produced polysaccharide matrix, which adheres to an inert or living surface. Several authors have stated that nearly 2/3 of chronic wounds contain bioburden in the form of biofilms. It has been reported that biofilm-associated infections exceeds $1 billion/year in the US. The objective of this study was to evaluate the ability of cadexomer iodine dressings to disrupt established biofilms in vitro over a 24 h period using single and mixed species biofilm models was investigated.

Methodology: Biofilms were grown in a 96-well microtitre plate where the lid was replaced by a specialized lid system with peg protrusions that sit directly into the wells. For each dressing tested, replicates were aseptically placed into appropriate wells of a fresh 96-well microtitre plate. Following two wash steps to remove excess stain and subsequent elution of the remaining stain in ethanol, the optical density (OD) at 570 nm was then measured for each well.

Key results:  Data were grouped into strong biofilm, moderate biofilm, weak biofilm or no biofilm categories. The results indicate that with the exception of S. aureus, the biofilms were disrupted in the presence of cadexomer iodine dressings when compared to filter paper controls.

Conclusions:

• P. aeruginosa produced a strong biofilm; in the presence of cadexomer iodine this was disrupted to a weak biofilm.

• S. aureus produced a strong biofilm; cadexomer iodine failed to substantially disrupt the biofilm formed.

• Mixed species Pressure Ulcer (PU) inoculum produced a moderate biofilm; in the presence of cadexomer iodine this was disrupted to a weak biofilm.

• Mixed species Diabetic Foot Ulcer (DFU) inoculum produced a strong biofilm; in the presence of cadexomer iodine this was disrupted to a moderate biofilm.