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New properties of nano-materials have made nanotechnology the leading part of biology and medical sciences. Due to their various biomedical properties, iron-based magnetic nanoparticles (MNPs) have been highly considered by biological researchers. Nowadays, increasing resistance to antibiotics is a major problem in treating clinical infections. Finding new antibacterial agents is therefore essential for the treatment of resistant strains. In this study, the iron oxide MNPs were produced using culture-medium supernatant of a newly isolated bacterium to investigate the inhibitory effects of the NPs on strains with a major role in clinical infections. Biosynthesis of iron oxide MNPs were detected by UV-Vis spectroscopy and the average size of particles was estimated by dynamic light scattering technique. The anti-bacterial activity of these NPs against E. coli and S. aureus was investigated using methods for the calculation of bacterial sensitivity coefficient. In the presence of NPs, the highest sensitivity coefficient value was observed for E. coli in 1xMIC concentration. On the other hand, S. aureus showed the lowest value. The death rate of the two strains in contact with NPs followed the first order kinetic equation and the survival rate decreased with the increase of exposure time. The results of this study as well as the high functionality of iron oxide MNPs, make its application desirable in the prevention and treatment of clinical infections.

 

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The occurrence of extended-spectrum beta-lactamases-producing bacteria is an important public health issue. The aim of this study was to investigate phenotypic and genotypic characteristics regarding the presence of extended spectrum β-lactamase ctx-m, per and ver producing Escherichia coli isolated from raw dairy samples. For this purpose, E. coli were isolated from 247 raw dairy samples (milk and cheese) in Yasooj in 2015-2017, and the isolates were screened for antibiotic resistance, extended spectrum β-lactamase and the presence of ctx-m, per and ver. In total, 200 isolates were selected. The highest frequency of resistance in isolates was against tetracycline (96.5%) and ampicillin (95.5%) antibiotics and the lowest against imipenem (12.5%), In addition, multidrug resistance against four or more antibiotics was observed in some isolates. Extended spectrum β-lactamase resistance was detected in 86 isolates (43%) and ctx-m, per and ver genes were detected in 82, 0 and 7 E. coli isolates, respectively. These findings demonstrated that raw dairy products may be reservoirs for the dissemination of β-lactam antibiotics and that resistance genes could be transmitted to humans through the food chain.

 

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Phenazine 1-corboxylic acid (PCA) is an antibiotic, which inhibits the growth of a vast number of micro-organisms. PCA has has been applied in fields such as pharmaceutical, agricultural, marine and chemical industries. In this study, the antibiotic properties of PCA (produced by pseudomonas aeruginosa MUT.3, which is kept at the Microbial Collection of Malek Ashtar University of Technology) was studied. The impacts of temperature and light conditions on the activity of PCA was investigated within a 230-day period. To investigate the rate of PCA destruction in the experiment, high performance liquid chromatography (HPLC) was utilized. Moreover, the antibacterial activity of PCA under various conditions was studied by minimum inhibitory (MIC) and minimum biocidal concentration (MBC) methods against E. coli DH5α. The results showed that PCA could be active up to 210 days in darkness (at 25^oC). Meanwhile, the antibacterial activity of PCA was reduced to 100 and 50 days by increasing the temperature to 35 and 45^oC, respectively. In addition, PCA could be active up to 120 and 10 days in visible and ultraviolet light condition, respectively. The MIC and MBC data were consistent with the HPLC results. Detailed data on the activity and stability of phenazine 1-corboxylic acid under various environmental conditions, as presented in this study, could be helpful in industries and healthcare services.
 
 

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Charcoal rot caused by Macrophomina phaseolina is one of the most important soil borne diseases with a broad host range including bean, which annually brings a significant damage to this plant. Biological control of charcoal rot is very important because its chemical control harms the environment, microflora and soil fertility. Chemical control of charcoal rot is also difficult and sometimes ineffective. Fluorescent Pseudomonads are able to increase plant growth and inhibit the development of plant pathogens by producing and secreting antibiotics, enzymes, siderophores, and plant hormones. In this study, infected bean plants by M. phaseolina were collected from infected bean fields of Khorramabad (Lorestan Province, Iran) in the summer of 2015. Virulence of fungal isolates was evaluated in a greenhouse and one isolate with the highest pathogenicity was chosen for further experiments. The biocontrol potential of eight Pseudomonas fluorescens strains, whose biocontrol abilities were proved in previous studies, was examined against M. phaseolina in vitro. The growth inhibition of M. phaseolina was examined by dual culture test and the antifungal activity of bacterial volatile and nonvolatile metabolites. P. fluorescens UTPf125, which showed the highest inhibitory effect on the mycelial growth, was selected for greenhouse tests. UTPf125 strain led to a significant reduction (%50) of disease severity and increased fresh and dry weight significantly. Phenol compounds were evaluated 1, 3, 5, 7 and 9 days after inoculation by pathogen. The results showed that the highest value of total phenol content was obtained on the third and fifth days after inoculation, decreasing on the seventh and ninth days.