One important virulence trait utilized by Staphylococcus aureus is the ability to form biofilms , this organism is able to adhere to and penetrate inside bovine mammary epithelial cells. In S. aureus polysaccharide intercellular adhesin (PIA) was encoded by icaA and icaD genes. Production of PIA is currently responsible for staphylococcal biofilm development. Biofilm Infections are generally chronic and difficult to treat. The aim of this study was to determine the prevalence of phenotypic and genotypic of biofilms from bovine mastitis infections in Iran. A total of 90 samples of Staphylococcus aureus were collected from raw milks of five dairy farms near Tehran. All of the samples were diagnosed according to the National mastitis council (NMC) methods. Staph aureus isolates confirmed by a polymerase chain reaction (PCR)-based method. In order to determine the biofilm formation capacity of the studied S. aureus strains, microtiter plate assay was performed. All the strains were screened for the presence of ica locus andicaA and icaD genes by PCR. The results of this study showed that 79 of 90 (87.7%) strains of S.aureus were found to possess the genes for biofilm production as evidenced by positive amplification of the ica locus as well as the icaA and icaD genes. The analysis of phenotypic by microtiter plate method showed that 4.4%, 40%, 43.3% of the S. aureus isolates produced strong, moderate or weak biofilm respectively, and 12.2% unable to produce biofilm.

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