A total of 140 samples of urine were collected from patients suffering from urinary tract infections (UTI) in Al-Yarmouk and Al-Karama hospitals in Baghdad. Samples were cultured (spreading) on MacConkey agar and blood agar and incubated at 37?C for 24 hr. Results showed that 89 samples gave positive culture for bacteria, and the primary identification led to detect 20 isolates belong to genum Proteus. A total of 140 samples of urine were collected from patients suffering from urinary tract infections (UTI) in Al-Yarmouk and Al-Karama hospitals in Baghdad. Samples were cultured (spreading) on MacConkey agar and blood agar and incubated at 37ºC for 24 hr. Results showed that 89 samples gave positive culture for bacteria, and the primary identification led to detect 20 isolates belong to genum Proteus. Occurrence of such isolates was highest in males 70% than in females 30%. Further identification declared that 75% of the isolates were belonged to Proteus mirabilis and 25% to Proteus vulgaris. Isolates of the first species were chosen for further experiments. When sensitivity of the Proteus mirabilis 15 isolates were tested against 13 commonly used antibiotic, results showed the ciprofloxacin was the most effective antibiotics against the isolates when resistance percentage of isolates was only 6.6%. While penicillin G, on the other hand, was the least effective one when 93.3% of the isolates resisted it . Depending on the antibiotic sensitivity results, one isolate of Proteus mirabilis PR15 was selected due to its multi-resistance of antibiotics, to be used for detecting its important virulent factors, namely swarming on the solid medium and motility in the semi-solid medium. The yeast Saccharomyces boulardii was used after insuring its sensitivity to Cycloheximide to detect its ability in producing inhibitory materials against Proteus mirabilis isolate, as well as its effect on the swarming and motility properties of the bacteria. Moreover, ability of the bacteria cells to adhere to the yeast cells was also investigated to avoid bacterial adhesion to the host cells. The yeast was propagated in two locally prepared media [dates extract broth (DEB) and dried tea leavies extract broth (DTLEB)] after enriched them with the other necessary nutrients. Growth of the yeast was also compared in two commercially used artificial media [sabauroud broth (SB) and yeast extract glucose peptone broth (YEGPB)]. To obtain best inhibitory effect, the yeast was propagated into four different liquid media, two ready to use and others locally prepared and two solid ready to use media. Results showed that liquid media were more efficient in exhibiting inhibitory activity of the yeast than the solid media when the first dilution concentrated of liquid media inhibited motility and swarming of the bacteria. To improve ability of the yeast in exhibiting inhibitory activity, various media, pH values, temperature and period of incubation were applied. Best activity was obtained when the yeast was propagated, separately, in sabauroud broth (SB) and yeast extract glucose peptone broth (YEGPB) media with pH 4.5 for 48 hr. at 37ºC. But in dates extract broth (DEB) and dried tea leavies extract broth (DTLEB) media with pH 5.5 under same other conditions. Minimum inhibitory concentrations (MIC,s) of yeast first diluted concentrated filtrates was determined in each of the four medium used, as well as its values against swarming and motility properties of Proteus mirabilis isolate. Results show that the filtrate totally inhibited swarming of the bacteria on the solid medium, and its motility in the semi-solid medium.