فهرست مطالب somayeh ataei jaliseh

Finding novel antimicrobials to treat drug-resistant Psudomonas aeruginosa is a major health challenge. In this study, ZnO nanoparticles functionalized by Thiosemicarbazone nanoparticles (ZnO@Glu-TSC NPs) were synthesized and the effect of the NPs alone and in combination with thymol on the expression of biofilm and efflux pump genes in P. aeruginosa was investigated. Physicochemical features of the ZnO@Glu-TSC NPs were evaluated by FT-IR, XRD, EDS-mapping, and SEM and TEM imaging. The inhibitory effect of ZnO@Glu-TSC NPs and thymol, alone and in combination, were determined by broth microdilution method, and quantitative PCR was used to evaluate the expression of the pelA, pslA, algD, mexA, mexB, and mexX genes. The synthesized NPs were almost spherical, without impurities, and in a size range of 20 to 60 nm. Simultaneous treatment of P. aeruginosa with ZnO@Glu-TSC and thymol had a significantly stronger inhibitory effect (MIC: 3.12-25.5 µg/mL) than either agent alone. The relative expression of the pelA, pslA, and algD genes in P. aeruginosa strains treated with ZnO@Glu-TSC+thymol was reduced by 0.44, 0.43, and 0.46 folds, respectively. Furthermore, the expression of mexA, mexB, and mexX genes decreased in P. aeruginosa strains treated with ZnO@Glu-TSC+thymol (0.42, 0.45, and 0.41 folds, respectively). Also, it was found that the combination of ZnO@Glu-TSC and thymol could synergically reduce the expression of the mentioned genes in comparison with either agent alone. This study showed that ZnO@Glu-TSC NPs and thymol synergically inhibited biofilm maturation and efflux pump systems in P. aeruginosa strains and could be considered a novel antibacterial candidate against P. aeruginosa strains.

Today, due to increase in resistance of antibiotics, it is necessary to find suitable alternatives to natural materials. Algae also have many applications in medicine, pharmacy and the food industry.  Therefore, the present study was performed to investigate the antibacterial activity of red algae Gracilaria gracilis extract. In this study, the active compounds of methanolic extract of red algae G. gracilis were identified by gas chromatography-mass spectrometry (GC/MS). The Antimicrobial effect of algae extract on bacteria were investigated by sequential dilution method. The chemical analysis of the algae extract compounds showed that the major components of the extract were phenylethine, silacyclopntenen, phthalic acid, n-hexadecanoic acid, dibutyl phthalate, phytol and gibberellin. In the study of minimum inhibitory concentration and minimum bactericidal concentration, it was shown that Pseudomonas aeruginosa and Staphylococcus aureus with algae extract with a minimum inhibitory concentration of 6.2 and 112.5 mg/mL, respectively, compared to other studied bacteria, showed more sensitivity. Based on the results, the methanolic extract of red algae G. gracilis had good antimicrobial activity. Therefore, clinical research is necessary for the clinical applications of this extract.