الفهرس 
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Abstract
Introduction: Uro-pathogenic E. coli (UPEC) is considered one of the members of the extra-intestinal pathogens, that predominantly cause urinary tract infections. Approximately 12% to 16% of adult hospitalized patients are supposed to have an indwelling urinary catheter at some time during their hospitalization, and this led to increased risk of acquiring CAUTI. Increasing rates of MDR E. coli is becoming a major public health problem that led to complication, treatment failure and increased rates of mortality and morbidity. MDR UPEC cause infections and lead to morbidity and mortality, they have different mechanisms of resistance, of which biofilm formation is the most important. The difficulty in eradicating a chronic infection associated with biofilm formation lies in the fact that biofilm bacteria can resist higher antibiotic concentration than bacteria in suspension. The Aim of this study: Assessment of the prevalence of MDR UPEC in catheterized patients admitted into Mansoura university hospital, then detection of biofilm production by isolated MDR UPEC strains, and finally testing the effect of silver nanoparticles on biofilm producing ability of the isolated strains. Materials and methods: 155 urine samples were processed to detect E. coli strains, Antibiotic susceptibility profile of resulting E. coli isolates was determined by Kirby- Bauer disc diffusion method to select MDR UPEC strains, then detection of biofilm production using tissue culture plate method among isolated MDR UPEC strains, and finally evaluation of anti-biofilm activity of silver nanoparticles (AgNPs) by re-detection of biofilm formation after incubation with various concentrations of silver nanoparticles. Results: Out of these urine samples, (35 isolates) (22.6%) showed E. coli. Out of them, (34 isolates) (97.1%) were MDR E. coli. (29 isolates) (85%) of MDR UPEC were biofilm producers. The antibiofilm effect was observed in dose dependent manner. Silver nanoparticles with concentration of 100μg/ml, recorded maximum antibiofilm effect (63.22%) followed by concentrations of 75, 50, and 25μg/ml which were able to eliminate the biofilm formation of MDR UPEC on the plate surface by (59.91%), (55.24%), (43.61%) respectively.