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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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Recently, milk exosomes have attracted much attention from researchers due to their availability and efficiency in cosmetic products and also as drug delivery nanocarriers. Since it is very important to find a simple and efficient method to purify these vesicles, in this research some methods of exosome isolation from bovine milk such as ultracentrifugation, using PEG polymer and several commercial kits were discussed and characterized. Detection of exosomes has been done using DLS and electron microscopy.
In ultracentrifugation, as the most common method of exosome isolation, the number of particles in the electron microscope images was estimated to be very low (5 ± 2 particles), while in the microscopic images of the Exosun kit, a large number of exosomes (150 ± 30 particles) was visible. In PEG precipitation, the average diameter of the particles in DLS results was 263 nm and more than the ultracentrifugation, Exocib and Anaexo kit, where the diameter of the particles was 176 nm, 142 nm, and 123 nm, respectively. The average diameter of the particles in the microscopic images of the Exosun kit was 30-70±10 nm, and DLS results confirmed the small size of the isolated particles. Considering the large number of small particles (≥ 30nm) in the microscopic results of the exosun kit, other methods may not have been able to isolate these small particles. Finally, although all the studied methods were able to isolate exosome from milk, more extensive studies are necessary to make a more accurate comparison and to introduce a standard method for isolating exosome from bovine's milk.

 

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The present study aimed to investigate the effect of some bio-elicitors and silver nitrate on the content of secondary metabolites in calli derived from leaf explants of silybum marianum. In this research, the best callus was achieved on MS medium containing KIN, thus this medium was chosen for further experiment. In the second experiment, leaf explants were cultured in a selected hormone-regulated medium. After 8 weeks of callus growth, bio elicitors including yeast Yarrowia lipolytica, fungus Aspergillus niger, and bacterium Pseudomonas putida in combination with silver nitrate as a non-living elicitor were added to the leaf-derived calli. Ten days after treatment, the phenolic compound content, antioxidant capacity, silymarin content, and PAL enzyme activity in the calli were measured. The results indicate that the simultaneous application of Yarrowia yeast and silver nitrate led to an improvement in the content of phenolic derivatives, silymarin, and PAL enzyme activity, and this was significant compared to other elicitors both with silver nitrate and without it. The researchers of this experiment suggest that the combined use of bio-elicitors especially Yarrowia lipolytica yeast, and silver nitrateinduces higher synthesis of medicinal metabolites in calli derived from leaf explants.