Sheyda Damoogh - Department of Microbiology, Faculty of Advanced Science and Technology, Tehran Medical Science, Islamic Azad University,Tehran, Iran.
Zeinab Niknan - Department of Microbiology, Faculty of Advanced Science and Technology, Tehran Medical Science, Islamic Azad University,Tehran, Iran.
Mehrad Vosough - Department of Biology, Faculty of Science, Nourdanesh Institute of Higher Education, Isfahan, Iran
Mahsa Taghipour Barogh - Department of Microbiology, Faculty of Advanced Science and Technology, Tehran Medical Science, Islamic Azad University,Tehran, Iran.
Sarvenaz Falsafi - Department of Microbiology, Faculty of Advanced Science and Technology, Tehran Medical Science, Islamic Azad University,Tehran, Iran.
Ava Behrouzi - Department of Microbiology, Faculty of Advanced Science and Technology, Tehran Medical Science, Islamic Azad University,Tehran, Iran.

Background and Aim : Escherichia coli Nissle ۱۹۱۷ (EcN; O۶: K۵: H۱) as a probiotic is attributed to a non-pathogenic and commensal E. coli. Special characteristics of this strain are the production of several antimicrobial substances such as microcins and β-defensin-۲. Gut-microbiota, by producing metabolites and conveying them to the host, plays a crucial role in the management of homeostatic and health conditions in the host. Methods : E. coli Nissle ۱۹۱۷ (EcN; Ardeypharm GmbH, Herdecke, Germany) strain was grown in Lauria-Bertani (LB) broth overnight at ۳۷℃ with shaking (۱۵۰ rpm). The cell-free supernatant was prepared according to the method proposed by Ogunbanwo. Fresh overnight pathogenic bacterial cultures were inoculated into Mueller Hinton Broth in ۹۶-well plates. The cell-free supernatant of E. coli Nissle۱۹۱۷ was prepared in different concentrations. Next, ۱۰۰ μl of each clinical pathogenic bacterial culture along with standard strain and ۱۰۰ μl of cell-free supernatant at various concentrations were mixed in each well in a final volume of ۲۰۰ μl. The lowest percentage of supernatant that can affect inhibition of growth bacteria was considered as the minimum inhibitory percentage (MIP).Results : RThe antimicrobial effect of E. coli Nissle۱۹۱۷ metabolites against ۱۰ clinical Pseudomonas aeruginosa and reference strain was characterized by the agar well diffusion assay. Zones of inhibition against all clinical samples and the standard strain showed that some clinical strains had significantly better inhibition zones compared to the other clinical strains. This result can reflect the different properties of each strain. Conclusion : Numerous studies have confirmed the inhibitory effect of different probiotics on various pathogenic strains. As well as our studies have shown E. coli Nissle۱۹۱۷ as a probiotic can have an inhibitory effect on clinical Pseudomonas aeruginosa strains. The supernatant of our probiotic evaluated in different concentration and our data demonstrated that they can result in growth inhibition in Pseudomonas aeruginosa strains.

Probiotic, E.coli, Pseudomonas aeruginosa, MIC