Antibiofilm Effect of Adamantane Derivative against Staphylococcus aureus

Abstract

Currently, one of the most urgent problems in clinical practice is the antibiotic therapy ineffectiveness at chronic diseases treatment caused by biofilms-forming microorganisms. One of the ways to its solution is the search for new compounds with antibiofilm activity which can prevent the adhesion of microorganisms, disrupt the structure of the biofilm matrix and affect the Quorum sensing system. The aim of the study was to investigate adamantane derivative 1-[4-(1-adamantyl) phenoxy]-3-(N-benzyl,N-dimethylamino)-2-propanol chloride (KVM-97) antimicrobial activity mechanism against Staphylococcus aureus biofilms. Methods. The ability of the adamantane derivative KVM-97 to prevent S. aureus biofilm formation and to destroy previously formed biofilms has been tested on polystyrene plates by gentian violet sorption on these structures, followed by desorption with organic solvent and use of resazurin (redox indicator). The S. aureus cells viability in mature biofilms was evaluated with specific dyes for living (acridine orange) and dead (propidium iodide) cells. Lowry method was used to assess the effect of KVM-97 on the matrix components for the total protein contents determination, the polysaccharides were detected spectrophotometrically (using phenol and sulfuric acid), Bap-protein – by test with Congo red. Persisters’ subpopulation was detected by activation of the SOS response in bacteria when exposed to high concentrations of antimicrobial substances. Results. It was found that KVM-97 (the compound with the adamantyl radical) showed an antibiofilm effect against S. aureus, decreasing biofilm biomass: at the biofilm formation stage – by 22.5% and 75.0%, while in case of 2-day biofilms treatment – by 34.5% and 32.4% at 0.5 MIC and 5.0 MIC respectively. Compound KVM-97 was able to reduce the number of metabolically active S. aureus cells only at the stage of biofilm formation (reduction by 92.7 and 95.8% at 2.0 and 5.0 MIC). Obtained results indicated that this adamantane-containing compound did not affect the protein and polysaccharides contents of S. aureus biofilms matrix. The changes of Bap-protein level caused by KVM-97 were not statistically significant (p>0.05). It was shown that KVM-97 did not prevent the formation of metabolically inactive persister cells; their share was 0.71% of the control. Conclusions. Thus, adamantane-containing compound KVM-97 is able to prevent S. aureus biofilm formation, causing significant biofilms’ mass reduction, as well as lowering the viable cells number in them and destroying already formed biofilms. Its antibiofilm effects are not associated with matrix protein and polysaccharides synthesis impairments. Further thorough investigations are needed to establish the effect of this compound on eDNA synthesis, the Quorum sensing system, and the ica and arg genes expression of S. aureus responsible for biofilm formation.