en Microbiology پژوهشي Research <div><strong>Background and objectives:</strong> Today, with the increasing rate of antibiotic resistance, treatment of bacterial infections has become challenging. Therefore, it is essential to find suitable alternative antibacterial compounds. The aim of this study was to investigate in vitro effects of silver nanoparticles and ethanolic extract of <em>Aloe vera</em> alone and combined on standard strains of some pathogenic bacteria<span dir="RTL">.</span><br> <strong>Methods:</strong> After collection and verification of <em>A. vera</em> plants, extraction was performed by the Soxhlet extractor method. Antibacterial effects of ethanolic extract of <em>A. vera</em> and silver nanoparticles on standard strains of <em>Staphylococcus aureus</em>, <em>Bacillus cereus</em>, <em>Escherichia coli</em> and <em>Pseudomonas aeruginosa </em>were investigated by agar well diffusion and tube dilution methods, respectively<span dir="RTL">.</span><br> <strong>Results:</strong> The ethanolic extract of <em>A. vera</em> and silver nanoparticles had antibacterial effects on the tested bacteria in a dose-dependent manner. &nbsp;The ethanolic extract of <em>A. vera</em> was more effective against <em>S. aureus</em> and <em>B. cereus</em> compared to gram-negative bacteria. However, silver nanoparticles were more effective against gram-negative bacteria (<em>P.</em> <em>aeruginosa</em> and <em>E. coli</em>). The effect of combination of ethanolic extract of <em>A. vera</em> and silver nanoparticles was much greater than the effect of either alone. This combination showed the greatest and lowest effect on <em>P. aeruginosa</em> and <em>S. aureus</em>, respectively.<br> <strong>Conclusion:</strong> For the first time, this study showed that the combination of ethanolic extract of <em>A. vera</em> and silver nanoparticles is effective against potentially pathogenic bacteria. Given the high rate of antibiotic resistance and side effects of conventional antibiotics, it is recommended to identify active compounds of this plant and evaluate the antimicrobial effects of this combination of fungi and other pathogenic bacteria both in vitro and in vivo.</div> Antibacterial susceptibility, Aloe vera, Nanoparticles, Silver, Plant extract 22 30 http://jcbr.goums.ac.ir/browse.php?a_code=A-10-248-1&slc_lang=en&sid=1 Abolfazl jafari-Sales a.jafari_1392@yahoo.com 10031947532846003695 10031947532846003695 Yes Department of Microbiology School of Basic Sciences, Kazerun Branch, Islamic Azad University, Kazerun, Iran Parisa Meshinchi taranoom.isc.isi@gmail.com 10031947532846003696 10031947532846003696 No Department of Chemical Engineering, University of Tabriz, Tabriz, Iran Ali Shabkhosh taranoom.iscc.isii@gmail.com 10031947532846003697 10031947532846003697 No Department of Microbiology School of Basic Sciences, Ahar Branch, Islamic Azad University, Ahar, Iran