Antibiofilm Efficacy of an Iodine Dressing and Comparator Dressings Against a Multispecies Biofilm, Anaerobic Biofilm and Fungal Biofilm

Abstract Body: Although biofilms can be formed by a single species, they are generally multispecies and can comprise of aerobic bacteria, anaerobic bacteria, fungi and yeasts. Biofilms are difficult to treat once formed, as they have increased tolerance to the immune system and antimicrobials that their planktonic counterparts are more susceptible to. Biofilm formation in wounds can lead to infection, increased inflammation and delayed wound healing. The aim of this study was to evaluate the antibiofilm efficacy of an iodine dressing and comparative antimicrobial dressings against a multispecies biofilm and also anaerobic and fungal biofilms.   Antibiofilm efficacy of Candida albicans was evaluated following an adapted version of ASTM E2871-13 ‘Standard test method for evaluating disinfectant efficacy against Pseudomonas aeruginosa biofilm grown in CDC biofilm reactor using single tube method’. Antibiofilm efficacy of a multispecies biofilm was evaluated by inoculating filter discs and incubating them on a nutrient hydrogel. Antibiofilm efficacy of Bacteroides fragilis was evaluated by growing the biofilm in a 12 well plate under anaerobic conditions. Following biofilm growth, dressings were hydrated and put in direct contact with the biofilms and incubated for 24 hours. Biofilms were added to a broad-spectrum neutraliser and sonicated, serial diluted and plated onto TSA. Plates were incubated at 37°C overnight and the following day colony counts were enumerated.   Following 24-hour treatment of C. albicans with an iodine dressing, no growth was observed, showing a 5-log reduction in fungal density (p 0.0277). Following treatment of a multispecies biofilm with an iodine dressing, nanocrystalline silver dressing, silver foam dressing and silver carboxymethlycellulose dressing no growth was observed showing a 7 log reduction in bacterial density (p < 0.05).   The iodine dressing shows potent antibiofilm efficacy against representative fungal, anaerobic and multispecies biofilms in vitro. The data shows the potential for the iodine dressing to treat and eradicate biofilms.