The influence of the chemical behaviour of iodine on the germicidal action of disinfectant solutions containing iodine

Despite centuries of research on this chemical element, the ability of iodine to form complexes with water-soluble polymers and various other molecules remains a topic of great interest. The fascination with iodine and iodophors arises from their remarkable antimicrobial properties against a wide range of pathogens. This review encompasses historical information on iodine and iodophors, showcases existing iodine-containing products available in the market, explores the diverse physicochemical methods employed to study polymer-iodine complexes, and assesses recently published studies on iodophors. Recent advances in this field include the use of new experimental techniques to get new insights into the mechanisms of complexation and structure of these complexes; preparation of iodophors using novel polymers, nano- and micro-particles; and fabrication of antimicrobial surfaces capable of slow iodine release.

There is no standard protocol for the evaluation of antiseptics used for skin and mucous membranes in the presence of interfering substances. Our objective was to suggest trial conditions adapted from the NF EN 13727 standard, for the evaluation of antiseptics used in gynecology and dermatology.

Three antiseptic solutions were tested in vitro: a chlorhexidine-benzalkonium (CB) combination, a hexamidine-chlorhexidine-chlorocresol (HCC) combination, and povidone iodine (P). The adaptation of trial conditions to the standard involved choosing dilutions, solvent, and interfering substances. The activity of solutions was assessed on the recommended strains at concentrations of 97% (pure solution), 50%, and 10% (diluted solution), and 1%. A logarithmic reduction ≥ 5 was expected after 60 seconds of contact, to meet requirements of bactericidal activity.

HCC did not present any bactericidal activity except on P. aeruginosa at a concentration of 97%. P was not bactericidal on E. hirae at any concentration and on S. aureus at 97%. CB had the most homogeneous bactericidal activity with a reduction > 5 log on the 4 bacterial strains at concentrations of 97%, 50% and 10%.

Adapting the NF EN 13727 standard allowed assessing the 3 tested solutions: only CB was bactericidal in dirty conditions. This study proved the possibility of validating antiseptic choice in vitro, in current practice conditions, for adjunctive treatment of skin and mucous membranes disorders, primarily of bacterial origin or with a potential of superinfection.

L’évaluation des antiseptiques à visée cutanéomuqueuse, en présence de substances interférentes, ne fait l’objet d’aucun protocole normatif. Notre objectif était de proposer des conditions d’essai adaptées de la norme NF EN 13727 pour l’évaluation d’antiseptiques utilisés en gynécologie et dermatologie.

Trois antiseptiques : une association chlorhexidine-benzalkonium (CB), une association hexamidine-chlorhexidine-chlorocrésol (HCC) et la povidone iodée (P) ont été testés in vitro. L’adaptation des conditions d’essai de la norme a concerné le choix des dilutions, du diluant et des substances interférentes. L’activité des produits a été évaluée sur les souches de la norme aux concentrations de 97 % (utilisation pure), de 50 % et 10 % (utilisation diluée) et de 1 %. Pour répondre aux exigences de bactéricidie, une réduction logarithmique ≥ 5 était attendue pour 60 secondes de contact.

HCC n’avait pas d’activité bactéricide à l’exception de la concentration à 97 % sur P. aeruginosa. P n’avait pas d’activité bactéricide sur E. hirae, quelle que soit la concentration testée, ni sur S. aureus à 97 %. CB avait l’activité bactéricide la plus homogène avec réduction > 5 log sur les 4 souches bactériennes à 97 %, 50 % et 10 %.

L’adaptation de la norme NF EN 13727 permet de discriminer les 3 produits testés : seul CB était bactéricide en conditions de saleté. Ce travail souligne la possibilité de valider le choix des antiseptiques in vitro dans des conditions représentatives de la pratique, dans le traitement d’appoint des affections cutanéomuqueuses primitivement bactériennes ou susceptibles de se surinfecter.

In this study, the resistance of biodegradable biomaterials, composed of blends of poly(ε-caprolactone) (PCL) and the polymeric antimicrobial complex, polyvinylpyrrolidone–iodine (PVP-I) to the adherence of a clinical isolate of Escherichia coli is described. Blends of PCL composed of a range of high (50,000 g mol⁻¹) to low (5000 g mol⁻¹) molecular weight ratios of polymer and either devoid of or containing PVP-I (1% w/w) were prepared by solvent evaporation. Following incubation (4 h), there was no relationship between m. wt. ratio of PCL in films devoid of PVP-I and adherence of E. coli. Conversely, microbial adherence to PCL containing PVP-I decreased as the ratio of high:low m. wt. polymer was decreased and was approximately 1000 fold lower than that to comparator films devoid of PVP-I. Following periods of immersion of PVP-I containing PCL films under sink conditions in phosphate buffered saline, subsequent adherence of E. coli was substantially reduced for 2 days (40:60 m. wt. ratio) and 6 days (100:0 m. wt. ratio). Concurrent exposure of PCL and E. coli to sub-minimum inhibitory concentrations (sub-MIC) of PVP-I significantly reduced microbial adherence to the biomaterial; however, the molecular weight ratio of PCL did not affect this outcome. Pretreatment of PCL with similar sub-MIC of PVP-I prior to inclusion within the microbial adherence assay significantly decreased the subsequent adherence of E. coli. Greatest reduction in adherence was observed following treatment of PCL (40:60 m. wt. ratio) with 0.0156% w/w PVP-I. In conclusion, this study has illustrated the utility of PVP-I as a suitable therapeutic agent for incorporation within PCL as a novel biomaterial. Due to the combined antimicrobial and biodegradable properties, these biomaterials offer a promising strategy for the reduction in medical device related infection.