Ag5IO6: novel antibiofilm activity of a silver compound with application to medical devices

This work explores the unique antibiofilm activity of pentasilver hexaoxoiodate (Ag5IO6). To test this activity, wound dressings were impregnated with Ag5IO6 and compared with various commercially available silver-containing dressings, as well as dressings containing chlorhexidine, iodine and polyhexamethylene biguanide (PHMB). The materials were tested against Pseudomonas aeruginosa, Staphylococcus aureus and Candida albicans for their ability to prevent micro-organism adherence, eliminate planktonic micro-organisms and disrupt/eliminate mature biofilms generated using the MBEC™ assay within 24 h of microbial exposure. Only the Ag5IO6-containing dressings were able to prevent adherence and eliminate surrounding planktonic micro-organisms for all species tested for ≥28 days of elution with log reductions >4. Two other silver dressings succeeded against P. aeruginosa only after 28 elution days, whilst the PHMB dressing succeeded after 28 days of elution against C. albicans only. Ag5IO6-containing dressings were able to generate >4 log reductions against all biofilms tested. The only commercial dressings able to generate >4 log reductions against biofilms were iodine against P. aeruginosa and S. aureus, and PHMB against S. aureus. The Ag5IO6 dressings demonstrated complete kill (>4 log reduction) in a standard 30-min planktonic log reduction assay against all species. These results demonstrate that Ag5IO6 has superior activity to a number of antimicrobials, with broad-spectrum efficacy that includes long-term prevention of microbial adherence, rapid kill of planktonic micro-organisms, and the ability to disrupt and eliminate mature biofilms. Thus, Ag5IO6 may be a valuable antimicrobial agent for use in a number of medical device applications, including wound dressings, various catheters or implants.