Tehran University of Medical Sciences Iranian Journal of Microbiology 2008-3289 9 6 2018 01 26 348 355 EN Roya Vahedi-Shahandashti Department of Microbiology, Faculty of Biological Sciences, Alzahra University, Tehran, Iran Rouha Kasra-Kermanshahi Department of Microbiology, Faculty of Biological Sciences, Alzahra University, Tehran, Iran Maliheh Shokouhfard Department of Microbiology, Faculty of Biological Sciences, Alzahra University, Tehran, Iran Parinaz Ghadam Department of Biotechnology, Faculty of Biological Sciences, Alzahra University, Tehran, Iran Mohammad Mehdi Feizabadi Department of Microbiology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran AND Thoracis Research Center, Imam Khomeini Hospital, Tehran University of Medical Sciences, Tehran, Iran Shahram Teimourian Department of Medical Genetics, Iran University of Medical Sciences, Tehran, Iran 2017 05 20 2017 11 09 Background and Objectives: Serratia marcescens, a potentially pathogenic bacterium, benefits from its swarming motility and resistance to antibiotic as two important virulence factors. Inappropriate use of antibiotics often results in drug resistance phenomenon in bacterial population. Use of probiotic bacteria has been recommended as partial replacement. In this study, we investigated the effects of some lactobacilli culture supernatant on swarming, motility and antibiotic resistance of S. marcescens. Materials and Methods: Antimicrobial activity of lactobacilli supernatant and susceptibility testing carried out on S. marcescens isolates. Pretreatment effect of lactobacilli culture supernatant on antibiotic - resistance pattern in S. marcescens was determined by comparison of the MIC of bacteria before and after the treatment. Results: Our results showed that pretreatment with L. acidophilus ATCC 4356 supernatant can affect the resistance of Serratia strains against ceftriaxone, but it had no effect on the resistance to other antibiotics. Furthermore, culture supernatant of lactobacilli with concentrations greater than 2%, had an effect on the swarming ability of S. marcescens ATCC 13880 and inhibited it. Conclusion: Probiotic bacteria and their metabolites have the ability to inhibit virulence factors such as antibiotic resistance and swarming motility and can be used as alternatives to antibiotics. https://ijm.tums.ac.ir/index.php/ijm/article/view/1360 https://ijm.tums.ac.ir/index.php/ijm/article/download/1360/773