Enhanced bactericidal effects of povidone-iodine in the presence of silver ions

The rising prevalence of antibiotic-resistant infections worldwide necessitates the development of innovative antimicrobial systems for effective pathogen control. This study investigates the synergistic bactericidal effects of a combined system comprising povidone-iodine (PVP–I) and silver ions (Ag(I)). The PVP-I/Ag(I) system exhibited enhanced bactericidal activity against four key surrogate bacterial species: two Gram-negative bacteria, Escherichia coli (E. coli) and Pseudomonas aeruginosa (P. aeruginosa), and two Gram-positive bacteria, Staphylococcus aureus (S. aureus) and Bacillus subtilis (B. subtilis). Our experiments revealed that Ag(I) interacts with iodide ions (I⁻) to form silver iodide (AgI). This reaction promotes the formation of hypoiodous acid (HOI), a more potent bactericidal agent than other reactive iodine species (RIS), by shifting the equilibrium of RIS released from PVP-I. Under representative conditions ([PVP-I]₀ = 1 mg/L, [Ag(I)]₀ = 5 μM, pH = 7.3), the concentration of HOI in the PVP-I/Ag(I) system was 2.4–3.9 times higher than in the PVP-I system alone, aligning with theoretical predictions. The bactericidal efficacy of the PVP-I/Ag(I) system was influenced by pH variations, affecting HOI formation. This system represents a promising tool for rapid and effective microbial control, potentially enhancing public health outcomes.