Use of Polyguanidine-Derivatives-Based Biocides for Microbial Growth Inhibition and for the Development of a Novel Polyethylene-Based Composite Material Resistant to the Formation of Multispecies Microbial Biofilms

This study aimed to investigate the dependence of the biocidal activity of polyguanidine (co)polymers on their structure during the formation of biofilms by active PE-degrading cultures of model microorganisms. The Bc-2 copolymer of methacryloyl guanidine hydrochloride (MGHC) and diallyldimethylammonium chloride (DADMAC), which suppressed both the formation of biofilms and the growth of planktonic cultures, exhibited the highest activity. When PE was exposed in tropical soil, the composition of the microbial community on the PE surface differed significantly from that of the community in the surrounding soil. In particular, the proportion of Actinobacteria increased from 7% to 29%, while the proportion of Bacteroidetes decreased from 38% to 8%. Keywords: biofilms, polyhexamethylene guanidine salts, dynamics of biofilm formation, antibiofilm effect, composite materials

eDNA Inactivation and Biofilm Inhibition by the Polymeric Biocide Polyhexamethylene Guanidine Hydrochloride (PHMG-Cl)

The choice of effective biocides used for routine hospital practice should consider the role of disinfectants in the maintenance and development of local resistome and how they might affect antibiotic resistance gene transfer within the hospital microbial population. Currently, there is little understanding of how different biocides contribute to eDNA release that may contribute to gene transfer and subsequent environmental retention. Here, we investigated how different biocides affect the release of eDNA from mature biofilms of two opportunistic model strains Pseudomonas aeruginosa ATCC 27853 (PA) and Staphylococcus aureus ATCC 25923 (SA) and contribute to the hospital resistome in the form of surface and water contaminants and dust particles. The effect of four groups of biocides, alcohols, hydrogen peroxide, quaternary ammonium compounds, and the polymeric biocide polyhexamethylene guanidine hydrochloride (PHMG-Cl), was evaluated using PA and SA biofilms. Most biocides, except for PHMG-Cl and 70% ethanol, caused substantial eDNA release, and PHMG-Cl was found to block biofilm development when used at concentrations of 0.5% and 0.1%. This might be associated with the formation of DNA–PHMG-Cl complexes as PHMG-Cl is predicted to bind to AT base pairs by molecular docking assays. PHMG-Cl was found to bind high-molecular DNA and plasmid DNA and continued to inactivate DNA on surfaces even after 4 weeks. PHMG-Cl also effectively inactivated biofilm-associated antibiotic resistance gene eDNA released by a pan-drug-resistant Klebsiella strain, which demonstrates the potential of a polymeric biocide as a new surface-active agent to combat the spread of antibiotic resistance in hospital settings.

Antimicrobial activity of polyhexamethylene guanidine hydrochloride derivatives against multi-resistant strains of microorganisms

The resistance of bacteria to the disinfectants used is one of the pressing health problems that need to be addressed in order to prevent the formation and spread of resistant strains. This leads to a sharp decrease in the effectiveness of anti-epidemic measures and contributes to maintaining a high level of morbidity. In the context of the growing incidence of HAIs, their polyetiology, the large adaptive potential of opportunistic microorganisms, and the growing resistance to antimicrobial drugs, it is necessary to search for new or modify the corresponding substances of plant or synthetic origin that have antimicrobial action and are used as antimicrobial agents. One of the representatives of this class of compounds are polyguanidines, characterized by high antimicrobial activity and low toxicity. Due to the high reactivity of the guanidine group, as well as the ease of synthesis and the relative availability of raw materials, N-phenyl- and N-octyl-substituted derivatives of polyhexamethylene guanidine hydrochloride were obtained by melt polycondensation, their molecular weight characteristics were determined, and the structure was investigated by IR spectroscopy. An earlier study of the acute toxicity of polyhexamethylene guanidine hydrochloride derivatives after a single oral intake of drugs into the body of laboratory animals (white mice) made it possible to establish the following LD50 values: polyhexamethylene guanidine hydrochloride - 850.0 ± 112.02 mg / kg; N-phenyl-substituted polyhexamethylene guanidine hydrochloride - 1399.9 ± 120.51 mg / kg; N-octyl-substituted polyhexamethylene guanidine hydrochloride - 1150.0 ± 137.40 mg / kg. The obtained values, according to the tabulation of hazard classes, allow the synthesized derivatives to be classified into the fourth hazard class and open up the possibility of using disinfectants as active components. The evaluation of the antibacterial properties of the samples was carried out by the method of serial dilutions in agar on hospital strains of bacteria and fungi isolated from the biomaterial of patients of the Republican Clinical Hospital named after N.A. Semashko, according to the clinical guidelines "Laboratory diagnosis of community-acquired pneumonia" 2014; "Bacteriological analysis of urine" 2014; "Determination of the susceptibility of microorganisms to antimicrobial drugs" 2015 It was found that N-substituted derivatives exhibit a greater antimicrobial effect in comparison with an unsubstituted polymer. The most sensitive to all the drugs presented are the yeast-like fungi Candida albicans (No. 2495) (complete suppression), as well as methicillin-resistant St. aureus (no. 2544), and the substituted samples almost completely suppress its growth. The most resistant strains are P. aeruginosa (No. 2281), A. Baumannii (No. 2806) and K. Pneumoniae (No. 3023), the percentage of reduction of these bacteria under the action of substituted samples does not exceed 41%, which is explained by their multi-resistance.

Synthesis and study of oligohexamethyleneguanidine hydroiodide as a radiopaque substance

Diagnosis of complex injuries, such as splinter fractures and wounds, skull injuries accompanied by internal injuries that are inaccessible to visual control, presents the greatest difficulties during X-ray examination. Therefore, it is relevant to develop a drug that can help localize the site of a pathological lesion with high accuracy, relying only on the results of an X-ray study, which is possible when a reference point (substance) is applied to the patient’s skin. A radiopaque contrast compound based on an iodinated polymeric matrix with iodine as the contrasting component and polyguanidine as the carrier has been proposed to be used as a reference point substance. The choice of this class of polymers stemmed from the fact that a positive charge is localized to a greater extent on the carbon atom of the guanidine group, which allows loading iodine anions into it. Protonation of pure guanidine with hydroiodic acid has helped obtain guanidine hydroiodide. This finding was confirmed by IR spectroscopy methods (a decrease in the intensity of bands in the region of 1,380, 880 cm−1 in comparison with guanidine, as well as broadening of the band of stretching vibrations of amino groups characteristic of guanidine salts) and X-ray phase analysis. Polyhexamethylene guanidine hydroiodide was synthesized based on hexamethylenediamine and iodine-containing guanidine salt using melt polycondensation. The results show that the aqueous solutions of samples under study absorb X-radiation and are the X-ray-positive substances (exposure radiation dosage E = 0.04 mSV).