Tehran University of Medical Sciences Iranian Journal of Microbiology 2008-3289 8 4 2016 12 19 263 273 EN Fatemeh Farid Afshar Department of Microbiology, Islamic Azad University of Tonekabon, Tonekabon, Iran Parvaneh Saffarian Department of Microbiology, Tehran Medical Sciences Branch, Islamic Azad University,Tehran, Iran Hamideh Mahmoodzadeh Hosseini Applied Microbiology Research Center, Baqiyatallah University of Medical Sciences, Tehran, Iran Fereshteh Sattarian Applied Microbiology Research Center, Baqiyatallah University of Medical Sciences, Tehran, Iran Mohsen Amin Department of Drug and Food Control and Pharmaceutical Quality Assurance Research Center, Faculty of Pharmacy, Tehran University of Medical Sciences, Tehran, Iran Abbas Ali Imani Fooladi Applied Microbiology Research Center, Baqiyatallah University of Medical Sciences, Tehran, Iran 2015 11 28 2016 07 17 Background and Objectives: Acinetobacter spp. are important causes of nosocomial infections. They possess various antibiotic resistance mechanisms including extended spectrum beta lactamases (ESBLs). The aim of this study was to determine antibiotic resistance profile of Acinetobacter clinical isolates especially among ESBL-producing strains and to investigate the antimicrobial effects of oleo-gum-resin extract and essential oil of Ferula gummosa Boiss. Materials and Methods: 120 Acinetobacter strains were isolated from various clinical samples of hospitalized patients in Baqiyatallah hospital, Tehran during 2011-2012. Antibiotic susceptibility test was performed on the isolates using disk diffusion method. To detect and confirm the ESBL-positive isolates, phenotypic and genotypic tests were performed. Three types of F. gummosa oleo-gum-resin extracts and essential oils were prepared and the bioactive components of F. gummosa Boiss extracts were determined by GC-Mass chromatography. F. gummosa antimicrobial activity was evaluated against standard strain of Acinetobacter baumannii (ATCC19606) as well as Acinetobacter clinical isolates using well and disk diffusion methods. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined by broth microdilution method. Results: 46 isolates were resistant to all tested antibiotics. All clinical isolates were resistant to cefotaxime. 12.94% of the isolates were phenotypically ESBL-producing among which 94.2% carried ESBL genes (blaPER-1, blaOXA-4 and blaCTX-M) detected by PCR. Oleo-gum-resin of F. gummosa had significant antibacterial activity and alcoholic essential oil had higher inhibitory effect on Acinetobacter strains (MIC of 18.75 mg/ml). Conclusion: Ferula gummosa extract contained components with well-known antimicrobial effects.   https://ijm.tums.ac.ir/index.php/ijm/article/view/824 https://ijm.tums.ac.ir/index.php/ijm/article/download/824/661