Tehran University of Medical Sciences Iranian Journal of Microbiology 2008-3289 9 1 2017 05 18 1 10 EN Elham Akbari-Ayezloy Students Research Committee, Urmia University of Medical Sciences, Urmia, Iran Nima Hosseini-Jazani Department of Microbiology, Faculty of Medicine, Urmia University of Medical Sciences, Urmia, Iran Saber Yousefi Department of Microbiology, Faculty of Medicine, Urmia University of Medical Sciences, Urmia, Iran Nazanin Habibi Students Research Committee, Urmia University of Medical Sciences, Urmia, Iran 2016 07 10 2017 04 15 Background and Objectives: Biofilm formation is an important virulence factor for methicillin-resistant Staphylococcus aureus (MRSA). Fosfomycin is a borad-spectrum antibiotic with inhibitory effects on biofilm production and β-Chloro-L-alanine (β-CLA) is an amino acid analog. The aim of this study was to determine effect of the combination of fosfomycin and β-CLA on biofilm production by MRSA isolates. Also,the clonal relatedness of the isolates was evaluated. Materials and Methods: To determine the ability of biofilm production by 42 MRSA isolates, microtiter plate method was used. Antibacterial activities of fosfomycin and β-CLA were investigated by determining MICs and MBCs. Antibiofilm activities were measured in the presence of sub-MIC concentrations of fosfomycin, β-CLA or a combination of both. RAPDPCR was used for investigating the clonal relationship between isolates by the two specific primers. Results: 21.4% of isolates were strong and 5% were moderate biofilm producers. The effect of fosfomycin plus β-CLA treatment on biofilm production was significantly different from non-treated, fosfomycin and β-CLA groups (p=0.00, 0.004 and 0.000 respectively). RAPD-PCR analysis revealed that the RAPD1 primer had more discriminatory power. The Sizes of RAPD-PCR bands ranged from 150 bp to 1500 bp and the number of bands varied from 1 to 13. Conclusion: Clonal relatedness of isolates showed that the majority of biofilm producing isolates had identical pattern and only three isolates showed more than 80% similarity. The combination of fosfomycin and β-CLA could be introduced as an excellent mixture for eradication of MRSA biofilms in vitro. https://ijm.tums.ac.ir/index.php/ijm/article/view/1087 https://ijm.tums.ac.ir/index.php/ijm/article/download/1087/694