Original Article | J Adv Med Biomed Res. 2022; 30(139): 154-161 Volume 30, March & April 2022 Journal of Advances in Medical and Biomedical Research Journal of Advances in Medical and Biomedical Research | ISSN:2676-6264 Evaluation of Specific Bacteriophage Against Salmonella infantis and Its Antibacterial Effects Compared to Ciprofloxacin in In Vitro Conditions Mohammad Reza Esmaeil Zadeh 1 , Mohammad Kazem Sharifi Yazdi 2,3 , Zahra Rajabi 4 , Farzaneh Amin Harati 1 , Farhad Nikkhahi 1,5 , Sara Sharifi Yazdi 6 , Gholamreza Hassanpour 7 , Alireza Monadi Sefidan 3 ,Mohammad Mehdi Soltan Dallal 1,4* 1. Dept. of Pathobiology, Faculty of Public Health, Tehran University of Medical Sciences, Tehran, Iran. 2. Zoonosis Research Center, Tehran University of Medical Sciences, Tehran, Iran 3. Dept. of Medical Laboratory Sciences, Faculty of Allied Medical Sciences, Tehran University of Medical Sciences, Tehran, Iran 4. Food Microbiology Research Center, Tehran University of Medical Sciences, Tehran, Iran. 5. Medical Microbiology Research Center, Qazvin University of Medical Sciences, Qazvin, Iran. 6. Medical Student, Faculty of Medicine, Tehran University of Medical Sciences, Tehran, Iran. 7. Center for Research of Endemic Parasites of Iran, Tehran University of Medical Sciences, Tehran, Iran Article Info ABSTRACT 10.30699/jambs.30.139.154 Background & Objective: Phage therapy could be used as an alternative method to antibiotic treatments. The purpose of this study was to evaluate the antibacterial activities of isolated lytic bacteriophage against ciprofloxacin-resistant strain of Salmonella infanits in vitro conditions. Materials & Methods: The standard strain of Salmonella infantis and its specific bacteriophage was isolated by soft agar method. Phage susceptibility to heat and pH was evaluated by the Double-Layer Agar method. In vitro assay was carried out on human epithelial type 2 (HEp-2) cells to investigate the effect of bacteriophage on the cytotoxic and invasion of Salmonella infantis to human epithelial cells. Results: Head and tail morphology of bacteriophages against Salmonella infantis were identified by transmission electron microscopy and assigned to the Myoviridae family. The results of the double-layer agar assay showed that the titer of bacteriophages was 1.8×10 7 PFU/ml. bacteriophage was stable at 4 ֯C and the best quantification of bacteriophage was determined at pH=8. The isolated bacteriophage was specific for Salmonella infantis and had no lytic activity against other pathogenic bacteria. In the evaluation of the binding and invasion of Salmonella infantis to the HEp-2 cell line, as expected, the lytic activity of specific bacteriophage was observed following inoculation. Conclusion: Additional studies are needed for better understanding of the interaction between phage, microorganisms and human host before applying phage therapy on a large scale. Keywords: Salmonella, Salmonellosis, Lytic bacteriophage, Ciprofloxacin Received: 2020/11/01; Accepted: 2021/03/14; Published Online: 31 Jan 2022; Use your device to scan and read the article online Corresponding Information: Mohammad Mehdi Soltan Dallal, Food Microbiology Research Center / Dept. of Pathobiology, Faculty of Public Health,Tehran University of Medical Sciences, Tehran, Iran E-Mail: : msoltandallal@gmail.com Copyright © 2021, This is an original open-access article distributed under the terms of the Creative Commons Attribution-noncommercial 4.0 International License which permits copy and redistribution of the material just in noncommercial usages with proper citation. Introduction Salmonella infections are spread primarily by conta- minated foods, poultry, eggs, and milk. An infection in humans can occur after drinking contaminated water or ingesting uncooked contaminated eggs, milk, and meat originating from poultry, cattle, or swine.Thus Salmonella infections represent a major concern to public health, animals, and food industry worldwide. Human health can be harmed as a result of direct contact with infected animals, blood, urine, and feces. Antibiotics have been used more often to suppress bacteria in animals and increase food production, hastening the proliferation of antimicrobial-resistant bacteria (1). When animals are kept on the farm the methods of transmission are usually more complex, and Salmonella strains and serotypes can remain on farms simultaneously for long periods (2). The primary method for identification is serotyping, with over 2400 serovars identified. Methods for discrimination within serovars of clinical and epidemiological import- ance include phenotypic tests such as phage typing. Divisions at different levels within serotypes are