Pseudomonas aeruginosa is one of the most important causes of infection in medicine, which in recent years is known as an antibiotic resistant bacterium. One of the antibiotic resistance strategies of this bacterium is algD and PpyR genes expression for biofilm formation.

   In recent years, it has been shown that using microorganisms, such as probiotics, is a method of pathogen bacterium harnessing, hence, in this study, for preventing biofilm formation of P. aeruginosa, E.coli Nissle 1917(EcN) probiotic bacterium is used, as a new treatment choice.

  Due to direct relationship between antibiotic resistance and biofilm formation, strains with the    

  highest antibiotic resistance was chosen by antibiogram test. Then, in order to determine the inhibition rate of EcN bacterium in the formation of biofilm caused by P. aeruginosa bacterium, a biofilm formation test was performed.

  At the end, to evaluate algD and PpyR genes expression, which were key parts of biofilm formation, in the presence of probiotic EcN bacterium, Real- time PCR method was used.

  Based on the results of the biofilm formation test, EcN bacterium showed a high inhibitory effect on the formation of biofilm caused by P. aeruginosa bacterium.

  .Also, in assessment of algD and PpyR genes expression in presence of EcN probiotic, a significant reduction in PpyR gene expression has been seen, in comparison with control group. The results of this study showed that EcN probiotic can act as a suitable new treatment option, to reduce P. aeruginosa biofilm formation.