Introduction: The widespread use of antimicrobials has many negative consequences for public health. Concern about microbial resistance to antimicrobials is growing in several areas, while strategies are being developed to better manage this problem. Biological methods are increasingly coming to the forefront in addressing the problem of microbial resistance and biofilms. Essential oils can serve as effective antimicrobial agents, as they have been shown to be effective in controlling resistant microorganisms and preventing the formation of biofilms, which are a major public health problem. In recent years, essential oils have been shown to be effective against bacterial strains that are otherwise resistant to antimicrobial agents. Purpose: The purpose of this master's thesis was to investigate the antimicrobial activity of carvacrol, eugenol, and limonene on E. coli, P. aeruginosa, and S. aureus and to evaluate their potential to prevent surface biofilm formation. Methods: Different concentrations of the components carvacrol, limonene and eugenol were used to determine the efficacy of the effect of each essential oil component on the growth and multiplication rate of selected bacteria. Bacteria, used as test microorganisms, were: E. coli, P. aeruginosa and S. aureus. The inhibitory and bactericidal potential of each component was analyzed by the microdilution method and the plate culture method, and the effect against biofilms was determined by the crystal violet staining method. Results: All tested active components showed both inhibitory and bactericidal activity on all tested bacteria. The results showed that the value of the optical density of the biofilm decreased with increasing concentration of the active compounds and the efficacy of the active compounds increased with increasing concentration. With the appropriate concentration of limonene, carvacrol and eugenol, more than 80 % of the biofilm of E. coli and P. aeruginosa can be prevented, while active components were less effective in preventing the formation of the biofilm of S. aureus (< 70 %). Discussion and conclusion: We found that carvacrol, limonene and eugenol have good potential to control planktonic cells and prevent biofilm formation. Developments in this area are relevant because more frequent use of essential oils could reduce the problem of microbial resistance and overuse of antibiotics. Further research is needed in this area to investigate the potential effect of the active components on different biofilms involving several different bacterial strains simultaneously.
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