eradication of methicillin resistant s. aureus biofilm by the combined use of fosfomycin and β-chloro-l-alanine

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. keywords: mrsa, fosfomycin, phosphomycin, β-chloro-l-alanine, biofilm, rapd-pcr