Tehran University of Medical Sciences Journal of Medical Bacteriology 2251-8649 9 1-2 2020 08 23 9 15 Fahimeh Pourzal Department of Pathobiology, School of Veterinary Medicine, Shiraz University, Shiraz, Iran. Masoud Haghkhah Department of Pathobiology, School of Veterinary Medicine, Shiraz University, Shiraz, Iran. 2019 07 01 Background:     Staphylococcus aureus is the most important etiological agent of biofilm associated-infections. It is one of the Gram-positive pathogens causing a wide range of nosocomial infections. Genes involved in biofilm formation is a defensive mechanism of this pathogen to combat the host immune response and remain stable in hostile environment. The aim of this study was to investigate prevalence of biofilm associated genes (BAGs). Methods:     Eighty samples of Staphylococcus aureus isolates from human infections were collected. Thirteen BAGs including rbf, sigB, sasG, icaA, sarA, icaR, icaD, clfA, clfB, fib, fnbpB, bap and fnbpA were amplified by PCR assay. Results:     The prevalence of genes were as follows:  sigB (93.7%) and sarA (90%) were the most prevalent BAGs followed by rbf (83.7%), fib (80%), sasG (78.7%), icaR (78.7%), clfB (78.7%), clfA (78.7%), fnbpA (73.7%), icaD (66.2%), icaA (50%), fnbpB (22.5%). However, bap was not detected in any isolate. Conclusion:     This study showed that the sensitivity and specificity of PCR is high in the identification of biofilm associated genes in S. aureus. However, researchers need new molecular methods to improve understanding of the exact role of the genes involved in biofilm formation. https://jmb.tums.ac.ir/index.php/jmb/article/view/424 https://jmb.tums.ac.ir/index.php/jmb/article/download/424/306