## 1 Introduction
Its mechanism of action involves interaction with negatively charged phospholipids of bacterial membranes, which results in the release of the main intracellular components, the occurrence of structural changes in proteins (precipitation) and cytolysis. Its activity is pH-dependent (the optimal pH for its action is 5.5-7.0). It has a killing effect against Gram-positive and Gram-negative bacteria, viruses and fungi, but it is not active against fungal spores [13]. There are scientific literature reports on the relationship between antibiotic resistance and CHG resistance. It has been proven that Gram-negative bacteria showing resistance to some antibiotics (e.g., imipenem, ciprofloxacin) may be resistant to CHG [14]. This compound is used in skin antiseptics (e.g., in the preparation called CITROclorex 2%) as well as in dentistry. It is considered the gold standard among mouthwashes with antibacterial properties [12]. Ocenidine dihydrochloride (_N_,_N_-(1,10 decanediyldi-1[4\(H\)]-pyridinyl-4-lidene) bis-(1-octanamino) dihydro) (OCT) is a non-volatile and surface-active substance. OCT is a stable compound, operating at a pH range of 1.6-12.2 [15]. The mechanism of action of OCT is to bind to negatively charged structures of microorganisms, e.g., the bacterial envelope, the cell membrane, polysaccharides and phospholipids. A result of this combination is cylolysis of the cell. OCT has a strong killing effect against Gram-positive and Gram-negative bacteria, fungi and enveloped viruses [16]. For a long time, bacteria have been susceptible to this compound; however, recent reports indicate possible adaptation of microorganisms to its high concentrations [17; 18; 19]. It is widely used to disinfect skin, mucous membranes and wounds, e.g., in the Octenisept preparation [20]. Polyhexanide biguanide (1-(diaminmethylidene)-2-hexylguanidine) (PHMB) is a positively charged compound that interacts with negatively charged bacterial structures. It also affects the operation of ion pumps, enzymes and cell receptors of microorganisms. PHMB is a colorless and odorless compound which is highly soluble in water and alcohol [21]. The killing spectrum of PHMB includes Gram-positive and Gram-negative bacteria, fungi, protozoa and the human immunodeficiency virus. However, the latest scientific data indicate gradual resistance of fungi and protozoa to PHMB [22]. This compound is considered safe and to have low toxicity compared to other antiseptics [23]. It is commonly used as an antiseptic in the medical and cosmetic industries (e.g., in Prontoderm Solution) and in the sanitization of recreational water [15]. Hypochlorous acid and other compounds, being sources of chlorine, are widely used in medicine as antiseptics (e.g., in Microdacyn 60 Wound Care) [24; 25]. These compounds are commonly used in endodontics, but they are quite toxic to aquatic organisms [26]. EOs, being volatile compounds, characterized by a strong aroma, constitute a source of substances with antiseptic properties. They are secondary plant metabolites that can be obtained by various methods, e.g., steam distillation, extrusion, solvent extraction or cold absorption in fats [27]. EOs consist of mixtures of various chemical compounds, including ketones, alcohols, aldehydes, esters and terpen. These compounds exhibit specific properties that are used in various industries [28]. The main ingredients of EOs include carvacrol, citronellol, geraniol, eugenol, farnesol, mentone, eucalypt (1,8-cineole), limonene, linalyl acetate and _trans_-anethole [29; 30; 31; 32]. The aim of this study was to analyze the interaction of selected commercial antiseptics (Braunol, CITROclorex 2%, Microdacyn 60 Wound Care, Octenisept and Prontoderm Solution) with natural products (carvacrol, \(\beta\)-citronellol, geraniol, eugenol, farnesol, (-)-menthone, eucalypt, limonene, linalyl acetate and _trans_-anethole) against the _S. aureus_ ATCC 43300 (MRSA) strain.