Iodine-Lithium-alpha-Dextrin (ILαD) against Staphylococcus aureus skin infections: A comparative study of in vitro bactericidal activity and cytotoxicity between ILαD and Povidone-Iodine.

As antimicrobial resistance continuously increases, revisiting old antimicrobial agents, modified to enhance efficacy and safety, becomes important. Iodine has been widely used for more than 150 years as a wound and skin disinfectant; it is an effective broad range bactericide, and to date, it lacks reports of resistance development. The most important iodine-based agent is Povidone-Iodine (PVP-I) which provides excellent antibacterial activity. However, its safety profile has been questioned.To evaluate the in vitro antibacterial efficacy and kinetic properties of a novel iodine-based compound, Iodine Lithium alpha-Dextrin (ILαD), against Staphylococcus aureus, and compare the in vitro cytotoxicity profiles of ILαD and PVP-I.An MIC microbroth dilution method was performed against 12 meticillin-resistant (MRSA) and 8 meticillin-sensitive (MSSA) S. aureus clinical isolates using ILαD and PVP-I. Time-kill and post-antibiotic effect studies of ILαD provided rate-of-kill information. MTT cytotoxicity assays were performed using three cell lines, treated with the MIC doses of ILαD and PVP-I.The MIC values of ILαD and PVP-I against the MRSA strains were 125 mg/L and 31.25 mg/L respectively. Time-kill and post-antibiotic effect studies of ILαD revealed a log10 reduction factor of 3 within 8h exposure at a 2xMIC dose; the post-antibiotic effect was calculated at 5±0.3h. Cell viability at the MIC dose of ILαD was slightly affected while the MIC dose of PVP-I exerted a strong cell growth inhibitory effect of 90-95%.ILαD could be a promising solution against staphylococcal infections as it is effective, does not promote the development of resistant strains and in vitro testing indicates that it may be safer than PVP-I. Further studies are justified to determine whether ILαD does indeed overcome the clinical limitations of PVP-I.