The essential oils of Inula viscosahave been commonly worldwide employed as a crude drug by people in Asia, the Middle East and Africa. Due to the development of antimicrobial resistance by the use of antibiotics among pathogenic bacteria, natural products extracted from the plants can be used as alternative strategies to reduce pathogenic bacteria from foods and patients.
The main aim of the present work was the extraction of essential oils from the leaves of Inula viscosa, an aromatic plant harvested in full bloom (March) from the mountainous region of Tessalah of Sidi Bel-Abbes (northwest Algeria) and the evaluation of their antibacterial properties against some bacteria such as E. coli, Ps. aeruginosa ATCC 27853, and St. aureus ATCC 25923, B. subtilus by using agar well diffusion method and by the study of bacterial growth in the absence and the presence of essential oils.
              The quantitative analyzes of essential oils of Inula viscosa by hydrodistillation showed a low yield with a value of 0.23% and the antibacterial activity of essential oils of Inula viscosa, different concentrations (1, 2, 4, 6, 8, 12 μl), which wasemulsified with Tween 80 and by using agar well diffusion method has indicated an excellent antibacterial activity by E. coli, S. aureus ATCC 25923, Ps. aeruginosa ATCC 27853 and Ba. cereus with a maximal diameter of inhibition zone 24, 13, 32, 22 mm respectively.
                Furthermore, the study of Ps. aeruginosa ATCC 27853 and S. aureus ATCC 25923growth in the absence (Control) and in the presence of the essential oils of Inula viscosa,  has manifested a considerable biomass reduction accompanied by unbalanced growth after adding of essential oils of Inula viscosa.