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

Abstract

As antimicrobial resistance continues to increase, 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 does not promote the development of resistant strains. 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. A minimum inhibitory concentration (MIC) microbroth dilution method was performed against 12 meticillin-resistant (MRSA) and eight meticillin-susceptible (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 MIC doses of ILαD and PVP-I. The MIC values of ILαD and PVP-I against the MRSA strains were 125mg/L and 31.25mg/L, respectively. Time-kill and post-antibiotic effect studies of ILαD revealed a log10 reduction factor of 3 within 8h of exposure at a 2×MIC dose; the post-antibiotic effect was calculated at 5±0.3h. Cell viability was affected slightly at the MIC dose of ILαD, 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 overcomes the clinical limitations of PVP-I.