The bacterium Enterococcus faecalis is an opportunistic pathogen known for its commensal life as part of the microbiota of various organic systems and it can also be found in the environment. It causes infections of the urinary system, infects skin and wounds, and is also a specific cause of endocarditis. It holds many virulent factors, of which the hydrophobicity of the cell surface, the ability to form biofilm, β-hemolytic activity and susceptibility to vancomycin are discussed in more detail in this paper. The aim of the thesis was to determine whether there are significant differences in in vitro conditions the virulence of E. faecalis strains isolated from the hospital, food and wastewater after statistical data processing. By investigating the hydrophobicity of the cell surface, it was concluded that the strains isolated from food have the highest hydrophobicity, while there was no significant difference between hospital isolates and those from wastewater. According to the method from the work of Stępień-Pyśniak (2019), the ability to form biofilm is divided into four categories and those isolated from a hospital source are the strongest biofilm producers followed by strains from food and strains from wastewater as the weakest biofilm producers. If the ability to form a biofilm is viewed only according to the measured optical density of the strains, the strongest biofilm producers are strains isolated from food, followed by isolates from wastewater and finally hospital isolates. Hemolysis was shown by 20,00% of strains from a hospital source, 16,67% from food and 26,67% from wastewater, while the Bonfferoni test indicates that the differences between the results of different strains are not statistically significant. Out of a total of thirty strains from each source, 10,00% showed resistance to vancomycin from a hospital source, 3,33% from food and 20,00% from wastewater. It can be concluded that after the conducted tests, the null hypothesis proved to be correct for all virulence factors except hemolytic activity.