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Bai L.,China National Center for Food Safety Risk Assessment | Wang L.,Institute for Nutrition and Food Hygiene | Yang X.,Centers for Disease Control and Prevention | Wang J.,Northwest University, China | And 8 more authors.
Frontiers in Microbiology | Year: 2017

Background: The emergence and spread of antimicrobial resistance has become a major global public health concern. A component element of this is the spread of the plasmid-encoded extended-spectrum b-lactamase (ESBL) genes, conferring resistance to third-generation cephalosporins. The purpose of this study was to investigate the molecular characteristics of ESBL-encoding genes identified in Escherichia coli cultured from diarrheic patients in China from 2013 to 2014. Materials and Methods: A total of 51 E. coli were confirmed as ESBL producers by double-disk synergy testing of 912 E. coli isolates studied. Polymerase chain reaction (PCR) and DNA sequencing were performed to identify the corresponding ESBL genes. Susceptibility testing was tested by the disk diffusion method. Plasmids were typed by PCR-based replicon typing and their sizes were determined by S1-nuclease pulsed-field gel electrophoresis. Multi-locus sequence typing (MLST) and phylogrouping were also performed. Broth mating assays were carried out for all isolates to determine whether the ESBL marker could be transferred by conjugation. Results: Of the 51 ESBL-positive isolates identified, blaCTX-M, blaTEM, blaOXA, and blaSHV were detected in 51, 26, 3, 1 of these isolates, respectively. Sequencing revealed that 7 blaCTX-M subtypes were detected, with blaCTX-M-14 being the most common, followed by blaCTX-M-79 and blaCTX-M-28. Of the 26 TEM-positive isolates identified, all of these were blaTEM-1 genotypes. All isolates contained one to three large plasmids and 10 replicon types were detected. Of these, IncFrep (n = 50), IncK/B (n = 31), IncFIB (n = 26), IncB/O (n = 14), and IncI1-Ir (n = 8) replicon types were the predominating incompatibility groups. Twenty-six isolates demonstrated the ability to transfer their cefotaxime resistance marker at high transfer rates. MLST typing identified 31 sequence types and phylogenetic grouping showed that 12 of the 51 donor strains belonged to phylogroup B2. Conclusion: This study highlights the diversity of the ESBL producing E. coli and also the diversity of ESBL genes and plasmids carrying these genes in China, which poses a threat to public health. © 2017 Bai, Wang, Yang, Wang, Gan, Wang, Xu, Chen, Lan, Fanning and Li.

Liu W.,Institute for Nutrition and Food Hygiene | Zhang N.,Institute for Nutrition and Food Hygiene | Li B.,Institute for Nutrition and Food Hygiene | Fan S.,Institute for Nutrition and Food Hygiene | And 4 more authors.
Chemical Papers | Year: 2014

A simple and fast analytical method for the determination of the main steroidal glycoalkaloids, α- chaconine and α-solanine, in commercial potato crisps, based on QuEChERS (Quick, Easy, Cheap, Effective, Rugged, Safe) extraction and ultra performance liquid chromatography coupled with an electrospray ionization triple-quadrupole tandem mass spectrometer (UPLC-MS/MS) in the multiple reaction monitoring mode was established and validated. The sample preparation procedure involves the extraction of the analytes with acidified acetonitrile and simultaneous liquid-liquid partitioning achieved by an addition of anhydrous magnesium sulfate and sodium acetate without any further clean-up steps. The limits of quantification (LOQs) for α-chaconine and α-solanine were 31 μg kg-1 and 16 μg kg-1 of fresh mass, respectively, at the signal-to-noise ratio (S/Ns) of 10. The method was applied in a survey of the content of α-chaconine and α-solanine in twenty commercial potato crisps from different brands. The results showed that all the products contained α-chaconine and α-solanine in widely varying concentrations. The amount of α-chaconine was higher than that of α-solanine in all samples. © 2014 Institute of Chemistry, Slovak Academy of Sciences.

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