Rapid broad-spectrum activity of molecular iodine against multidrug-resistant bacterial and fungal pathogens without residual staining

ABSTRACT Povidone iodine (PVP-I) is a widely used topical antiseptic with broad antimicrobial activity, but its clinical utility can be limited by skin irritation, slow drying, and persistent staining of skin, textiles, and surfaces. Here, we evaluated reformulated molecular iodine (I 2 ) products as potential non-staining alternatives with retained or enhanced antimicrobial efficacy. Three I 2 formulations (soak, nasal antiseptic, and hand ointment) were tested against 17 clinically relevant bacterial and fungal pathogens, including multidrug-resistant organisms and emerging nosocomial pathogens. Antimicrobial performance was assessed by quantitative kill assays, textile staining studies, and persistence testing on dried surfaces. All three I 2 formulations demonstrated broad-spectrum activity against all organisms tested, with rapid 3–4 log 10 reduction in colony-forming units (CFUs) or >99.9% killing commonly achieved within 15 s; selected fungal species required longer contact times or higher concentrations for maximal activity. Potent activity was observed against major healthcare-associated bacterial pathogens, including Staphylococcus aureus , Enterococcus faecalis , Klebsiella pneumoniae , and Pseudomonas aeruginosa , as well as fungal pathogens including Candida albicans and Candidozyma auris . Compared with PVP-I, I 2 exhibited minimal residual staining and was readily removed from porous hospital textiles after brief water rinsing. Surface persistence studies further demonstrated sustained antimicrobial activity after drying. These findings indicate that I 2 retains the broad-spectrum efficacy of traditional iodophors while offering practical advantages in material compatibility and reduced residual staining. I 2 formulations may, therefore, represent useful alternatives for topical antisepsis and environmental decontamination in high-throughput healthcare settings where both antimicrobial performance and staining-related costs are important considerations.