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The aim of the current study was to determine the prevalence of resistance to some antimicrobial agents in commensal Escherichia coli from poultry in Bulgaria. It was performed from June to December 2020 and included 175 strains, 99 of which were isolated from broilers and 76 from laying hens. ESBL phenotypes of isolates were tested for the presence of blaCTX-M-1. The distribution of genes qnrS, qnrA and qnrB1 conferring resistance to quinolones was studied. Also, the resistance to tetracycline and the presence of tetA gene were investigated. A high percentage of resistance towards tetracycline and ciprofloxacin was observed in commensal E. coli isolates from broilers (65.6%, 70.7%, respectively), and a high percentage of resistance to ciprofloxacin (75.0%) in isolates from laying hens. Also, high resistance towards β-lactams ampicillin and amoxicillin/clavulanic acid was observed in isolates from broilers (54.5%, 45.4%), vs 50.0% to ampicillin and 39.5% to amoxicillin/clavulanic acid in isolates from laying hens. Fewer strains resistant to cefotaxime and ceftazidime (8.1 %, 7.1%) were found out in isolates from broilers. None of commensal E. coli strains from laying hens were resistant to cefotaxime and ceftazidime. Five of the cephalosporin-resistant E. coli from broilers (5.0%) were identified as producers of ESBL, possessing the gene blaCTX-M-1. Sixty-five strains from broilers (65.6%) and 50 strains from laying hens (65.8%) possessed the qnrS gene. The qnrA and qnrB1 genes were not detected in ciprofloxacin-resistant E. coli isolates. Sixty-five strains from broilers (65.6%) and 33 strains from laying hens (33.0%) possessed the gene tetA. The commonest profile of multidrug resistance in E. coli isolates from broilers (37.4%) included ampicillin, amoxicillin/clavulanic acid, tetracycline and ciprofloxacin while in isolates from laying hens, resistance to ampicillin, amoxicillin/clavulanic acid and ciprofloxacin predominated (33.0%). [ABSTRACT FROM AUTHOR]

Irradiation of trans-2-phenylcyclohexyl 4-cyanobenzoate (4) in methanol results in formation of the 1-phenylcyclohexene and 4-cyanobenzoic acid as the major products. The mechanism proposed for this example of the Norrish Type II-like reaction, normally inefficient for the [pi], [pi] * state of esters, begins with intramolecular electron transfer in the excited singlet state. The next step, intramolecular proton transfer, is highly exergonic as a result of the increased acidity of the benzylic hydrogen of the radical cation and the increased basicity of the carbonyl oxygen of the radical anion. The final step is cleavage of the 1,4-biradical. This mechanism is proposed on the basis of product studies, absorption spectra, fluorescence spectra, oxidation and reduction potentials, and nanosecond laser flash photolysis spectra. The stereochemical requirements for the process have also been examined using solution NMR, the X-ray structure, and MM3 calculations. The stereoisomer, cis-2-phenylcyclohexyl 4-cyanobenzoate (5), undergoes cis to trans isomerization before photofragmentation. Pbotolysis of the cis isomer in methanol--OD demonstrated that the cis to trans isomerization occurred by inversion at C1. Key words: Norrish Type II, aromatic esters, intramolecular electron transfer.

The photolysis of ten substituted arylalkyl esters in methanol leads to the formation of phenol and tert-butyl-substituted phenols via photo-Fries reaction. The substituent effects and photochemical efficiency of the reactions are discussed.

The optimal parameters of the extraction process for the extraction of biologically active substances from the dried fruits of black blueberry have been established and experimentally confirmed. The phenolic complex of the extracts obtained at different parameters of the extraction process was investigated - selection of the extractant; extraction temperature; extraction time and hydromodule. Studied are the extracts obtained at the optimals extraction parameters for total phenols 7,34 g gallic acid / 100 g dry substance, phenolcarboxylic acids 0,61%, flavonoid phenolic compounds 194 mg%, sum anthocyanins 115 mg% and tannins 8,76 g catechin / 100g dry substance. On the basis of the experimental data, the technological regimes of the extraction process were selected. The use of 70% C2H5OH as an extractant is technologically warranted to produce extracts of dried fruits black blueberry with maximum content of phenols, flavonoids, anthocyanins and tannins. Technologically justified extraction temperature is 65-80°C. By increasing the extraction temperature to 80°C, the quantity of anthocyanins in the extracts increases, which positively affects the organoleptic evaluation of the final products. The optimum extraction time is 3-4 hours. During this extraction period, a maximum content of the phenolic complex is obtained. The results obtained suggest that the most advantageous hydromodul for extraction is 1:30. [ABSTRACT FROM AUTHOR]