Evaluation of antibacterial effect of silver nanoparticles against Escherichia coli isolates producing broad-spectrum beta-lactamases isolated from urinary tract infections

Introduction Considering the growth of antibiotic resistance and the study of new ways in Nanobiotechnology, this study examines the therapeutic effect of silver nanoparticles on E.coli bacteria to control and find new treatments against ESBL isolates of Escherichia coli. Materials and Methods For 100 samples of Escherichia coli, antibiotic resistance was determined by disc method for 3rd generation cephalosporin antibiotics and then for DDT confirmatory isolates. The effect of silver nanoparticles on ESBL isolates by well diffusion method and further on MIC and MBC was also done. SPSS software was used to analyze and evaluate the results and in all cases p <0.05 was considered significant Results The rate of resistance to 3 antibiotics of the third generation cephalosporin in this study was 45%, 20%, and 44%, respectively. A confirmation test in the presence of Clavulanic acid showed that 85.5% of the samples were an ESBL and the most inhibitory effect of silver nanoparticles was obtained by diffusion method at concentrations of 4000 ppm, 2000, 1000. The highest MIC values belonged to the concentration of 15.62 ppm and the lowest MIC concentration was 7.8 ppm. In determining MBC in isolates, the highest and lowest concentrations with a fatal effect were 62.5 ppm and 7.8 ppm, respectively. Conclusion The minimum concentration of nanosilver is 7.8 ppm and MBC obtained to eliminate E.coli 7.8 ppm.  Therefore, the colloid silver nanoparticle solution exhibits an excellent antibacterial activity at low concentrations.