C. jejuni is one of the most common causes of gastroenteritis in humans. Bacteria are capable of adhesion to surfaces and biofilm formation. Biofilm protects cells against external influences, which can be a major problem for consumer safety. One of the mechanisms of resistance to antimicrobial substances is efflux pumps. Their task is the secretion of toxic antimicrobial compounds from the cell. They also contribute to the increased resistance of bacteria. CmeABC, CmeDEF and CmeGH efflux pumps are found in C. jejuni. In the thesis we used wild type strain C. jejuni NCTC 11168 and five mutants with deletion into cmeB, cmeR, cj1687, cmeF and cmeG. We used winter savory ethanol extract and benzalkonium chloride. The purpose was: (i) to determine the ability of the bacteria to form biofilm on the steel surface; (ii) to determine the resistance of the formed biofilm on the polystyrene surface of efflux pump mutants and wild type strain to the select antimicrobial substances; and (iii) to determine the resistance of biofilm cells to these antimicrobial substances. We found that C. jejuni bacteria are capable of adhesion on polystyrene and stainlesss steel. Mutants in cj1687, cmeF and cmeG have lower ability to form biofilm on a steel surface, which proves the involvement of efflux pump systems in the mechanism of biofilm formation. Efflux pumps are actively involved in the resistance of a formed biofilm, since the biofilm of mutans was less resistant to winter savory extract and more resistant to benzalkonium chloride. Efflux pumps are involved in the resistance mechanism of biofilm and planktonic cells against winter savory extract and benzalkonium chloride.