en 35633983 <p style="text-align:justify"><span style="font-size:11pt"><span style="font-size:9.5pt">Background:</span><span style="font-size:10.0pt"> The purpose of the present study was to investigate the antimicrobial effects of berberine and thioridazine, as well as their effect on the gene expression of the AdeABC efflux pump system in Multidrug-Resistant (MDR)<em> Acinetobacter baumannii</em> (<em>A. baumannii</em>) isolates.</span></span></p> <p style="text-align:justify"><span style="font-size:11pt"><span style="font-size:9.5pt">Methods:</span><span style="font-size:10.0pt"> This study was carried out in five MDR clinical isolates of <em>A. baumannii</em> and a sample of standard strain (<em>A. baumannii</em> PTCC1797). The effect of Minimum Inhibitory Concentration (MIC) and the Minimum Bactericidal Concentration (MBC) of berberine, thioridazine, and ciprofloxacin alone and their combination on <em>A. baumannii</em> was evaluated by broth microdilution method. Also, their effect on the expression of <em>adeB</em> efflux pump gene was evaluated using real time PCR method. &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; </span></span></p> <p style="text-align:justify"><span style="font-size:11pt"><span style="font-size:9.5pt">Results:</span><span style="font-size:10.0pt"> The MIC of thioridazine, berberine, ciprofloxacin+thioridazine, ciprofloxacin+ berberine, thioridazine+berberine, and ciprofloxacin+thioridazine+berberine on MDR <em>A. baumannii</em>&nbsp;isolates was 64, 256, 128, 256, 128, and 128<em> &mu;g/ml</em>, respectively. The results showed that treatment of strains with thioridazine alone and in combination with berberine and ciprofloxacin significantly (p&lt;0.05) decreased the expression of <em>adeB</em> efflux pump gene.</span></span></p> <p style="text-align:justify"><span style="font-size:11pt"><span style="font-size:9.5pt">Conclusion:</span><span style="font-size:10.0pt"> Due to the inhibitory effects of thioridazine on bacterial isolates and<em> adeB</em> efflux pump gene, this compound can be used as a potential antimicrobial agent against MDR A. <em>baumannii.</em></span></span></p> Acinetobacter baumannii, Ciprofloxacin, Gene expression, Real time polymerase chain reaction, Thioridazine 132 136 https://www.ajmb.org/En/Article.aspx?id=60496 https://www.ajmb.org/PDF/En/FullText/60496.pdf FereshtehAhmadi Student Research Committee, Yasuj University of Medical Sciences, Yasuj, Iran91838Bahman Khalvati Medicinal Plants Research Center, Yasuj University of Medical Sciences, Yasuj, Iran91839Saba Eslami Shiraz University of Medical Sciences, Shiraz, Iran91840MehdiMirzaiiFaculty of Medicine, Shahroud University of Medical Sciences, Shahroud, Iran1067Narges Roustaei Department of Epidemiology and Biostatistics, School of Health and Nutrition Sciences, Social Determinants of Health Research Center, Yasuj University of Medical Sciences, Yasuj, Iran91842Farzad Mazloomirad Student Research Committee, Yasuj University of Medical Sciences, Yasuj, Iran91843Seyed SajjadKhoramroozDepartment of Microbiology, School of Medicine, Yasuj University of Medical Sciences, Yasuj, Iran31610