153 Abstract Background: Microbial biofilms are responsible for many human infections and increase of antibiotic resistant bacteria. Therefore, finding an efficient way to prevent infection and biofilm formation of bacteria is essential. Medicinal plants are among suitable candidates to inhibit biofilm formation of bacteria. The aim of this study was to evaluate the antimicrobial effects of Trachyspermum, Thymus and Pistachio (T.T.P) combined extracts (methanolic and ethanolic) against six pathogenic bacteria in planktonic and biofilm forms. Methods: The antibacterial activities of T.T.P combined extracts against planktonic form of pathogenic bacteria were evaluated by disc diffusion and macro-broth dilution methods. Also, anti- biofilm activity of the combined extracts was evaluated by microtiter plate method. Results: The results of disc diffusion analysis (MBC and MIC) showed that both methanolic and ethanolic extracts of T.T.P combined extracts were efficient for inhibition of planktonic forms of bacteria, although ethanol extract was more effective compared to the methanolic extract. The T.T.P combined extracts had inhibitory effect against biofilm formation of pathogenic bacteria. Also, these extracts efficiently demolished biofilm formation and prevent metabolic activity of bacteria in biofilm structures. The concentration of each extract had a direct relationship with its inhibitory effect. The maximum inhibitory effects of T.T.P combined extracts on biofilm formation, demolish of biofilm structure and inhibition of the metabolic activity of bacteria in the biofilm were 95.3% for P. aeruginosa, 97.2% for P. aeruginosa and 81.16% for E. coli . Conclusion: The results of this research demonstrated that T.T.P combined extracts can be used as an alternative component with inhibitory effect against pathogenic bacteria in planktonic and biofilm forms. developed in the left eye. Two patients had no family history suspicious for keratoconus. Copyright: 2018 The Author(s); Published by Kerman University of Medical Sciences. This is an open-access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Citation: Masoumipour F, Hassanshahian M, Jafarinasab T. Antimicrobial Activity of Combined Extracts of Trachyspermum, Thymus and Pistachio against Some Pathogenic Bacteria. Journal of Kerman University of Medical Sciences, 2018; 25 (2): 153-163. JKMU Journal of Kerman University of Medical Sciences, 2018; 25 (2): 153-163 Antimicrobial Activity of Combined Extracts of Trachyspermum, Thymus and Pistachio against Some Pathogenic Bacteria Fatemeh Masoumipour, M.Sc. 1 , Mehdi Hassanshahian, Ph.D. 2 , Tayebeh Jafarinasab, 1 1- MSc of Microbiology,Department of Biology, Faculty of Science, Shahid Bahonar University of Kerman, Kerman, Iran 2- Associate Professor of Microbiology, Department of Biology, Faculty of Science, Shahid Bahonar University of Kerman, Kerman, Iran (Corresponding author; mshahi@uk.ac.ir) Received: 3 November, 2017 Accepted: 8 June, 2018 ARTICLE INFO Article type: Original article Keywords: Antibiotic resistant Antibacterial activity Biofilm Medicinal plants Introduction Infectious diseases are common widespread diseases in the world which impose expenses on human societies. The rate of death resulting from these diseases is growing. Antibiotics are one of the main medicines to treat infectious diseases. Nowadays, due to the vast use of antibiotics, the resistance of bacteria to antibiotics has been increased (1-3). One of the reasons for antibiotic-resistant bacteria is forming the biofilm and it has been converted to one of the serious problems in infections. Biofilms are attached organizations of