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 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 8 h 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.
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