Saponins in the Camellia sinensis seeds have a broad spectrum of biological properties and application potentials. However, up to now, no chromatographic methods have been developed to provide full fingerprinting and quality assurance for these saponins. This research aimed to develop a novel method to tentatively identify and quantify saponins in C. sinensis seeds by ultra-high-performance liquid chromatography coupled with photo-diode array detector and quadrupole time-of-flight mass spectrometry (UPLC-PDA-QTOF-MS/MS), and compare it with the classic vanillin-sulfuric acid assay. Fifty-one triterpene saponins, including six potentially new compounds, were simultaneously detected by UPLC-PDA-MS/MS, and their chemical structures were speculated according to the retention behavior and fragmentation pattern. The total saponin content in the crude extract and the purified saponin fraction of C. sinensis seeds were quantified to be 19.57 ± 0.05% (wt %) and 41.68 ± 0.09% (wt %) respectively by UPLC-PDA at 210 nm, while the corresponding values were determined to be 43.11 ± 3.17% (wt %) and 56.60 ± 5.79% (wt %) respectively by the vanillin-sulfuric acid assay. The developed UPLC-PDA -MS/MS method could determine specified saponins, and is more reliable for quantifying the C. sinensis seed saponins than the classic spectrophotometric method. It is of great significance for the future investigations and applications of these saponins.
This study surveyed the prevalence of mcr-1 in extended-spectrum--lactamase (ESBL)-producing Escherichia coli strains of food origin in China and identified strains that carried mcr-1, fosA3, and ESBL genes, which were carried in various plasmids. The mcr-1 and ESBL genes could be cotransferred by one or more types of plasmids. The presence of these multidrug-resistant E. coli strains in food products might pose a huge threat to public health.KEYWORDS mcr-1, fosA3, ESBL-producing E. coli, transmission, circular intermediate, Tn6330, plasmids C linical and public health problems due to multidrug-resistant (MDR) bacterial infections have been further aggravated in recent years following the emergence of bla NDM-1 , a resistance gene that can mediate development of carbapenem resistance in the host strain and possesses the ability to disseminate rapidly among various species of bacterial pathogens worldwide (1, 2). Polymyxins have been regarded as the antibiotic of last resort to treat severe infections caused by carbapenem-resistant Enterobacteriaceae (CRE). Recently, a new plasmid-mediated colistin resistance mechanism, mediated by the MCR-1 protein, a phosphoethanolamine transferase that modifies bacterial lipid A through modification of its phosphoethanolamine moiety, was discovered (3). Since the initial discovery of mcr-1-positive Enterobacteriaceae strains in China in 2015, this resistance mechanism has been reported in various parts of the world (3, 4). However, there is still a lack of comprehensive information regarding the prevalence of mcr-1 in Escherichia coli of food origin. This study reports the isolation and characterization of foodborne E. coli strains that carried mcr-1, fosA3, and ESBL genes.A total of 408 nonrepeated cefotaxime-resistant E. coli isolates were obtained from 828 retail food samples (484 pork, 76 beef, 143 chicken, and 125 shrimp) purchased from open-air markets and supermarkets in Shenzhen, China, during the period of 10 August 2015 to 22 February 2016. E. coli isolates were selected on MacConkey agar plates supplemented with 2 g/ml cefotaxime and identified by matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) using a Bruker MicroFlex LT mass spectrometer (Bruker Daltonics). E. coli isolates were further confirmed by API20E test strips (bioMérieux, Inc.). All the E. coli strains were subjected to antimicrobial susceptibility testing for 11 antimicrobials using the agar dilution method according to the CLSI guidelines (5). All isolates were shown to be resistant to ampicillin, cefotaxime, ceftriaxone, and sulfamethoxazole-trimethoprim. They also exhibited resistance to other antibiotics, such as tetracycline (96%), nalidixic acid (84%), chloramphenicol (86%), Citation Liu X, Li R, Zheng Z, Chen K, Xie M, Chan EW-C, Geng S, Chen S. 2017. Molecular characterization of Escherichia coli isolates carrying mcr-1, fosA3, and extended-spectrum-β-lactamase genes from food samples in China. Antimicrob Agents Chemother 61:e00064-17.
Introduction Emergence of resistance determinants of bla NDM and mcr-1 has undermined the antimicrobial effectiveness of the last line drugs carbapenems and colistin. Aim This work aimed to assess the prevalence of bla NDM and mcr-1 in E. coli strains collected from food in Shenzhen, China, during the period 2015 to 2017. Methods Multidrug-resistant E. coli strains were isolated from food samples. Plasmids encoding mcr-1 or bla NDM genes were characterised and compared with plasmids found in clinical isolates. Results Among 1,166 non-repeated cephalosporin-resistant E. coli strains isolated from 2,147 food samples, 390 and 42, respectively, were resistant to colistin and meropenem, with five strains being resistant to both agents. The rate of resistance to colistin increased significantly (p < 0.01) from 26% in 2015 to 46% in 2017, and that of meropenem resistance also increased sharply from 0.3% in 2015 to 17% in 2017 (p < 0.01). All meropenem-resistant strains carried a plasmid-borne bla NDM gene. Among the colistin-resistant strains, three types of mcr-1 -bearing plasmids were determined. Plasmid sequencing indicated that these mcr-1 and bla NDM -bearing plasmids were structurally similar to those commonly recovered from clinical isolates. Interestingly, both mcr-1 -bearing and bla NDM -bearing plasmids were transferrable to E. coli strain J53 under selection by meropenem, yet only mcr-1 -bearing plasmids were transferrable under colistin selection. Conclusion These findings might suggest that mobile elements harbouring mcr-1 and bla NDM have been acquired by animal strains and transmitted to our food products, highlighting a need to prevent a spike in the rate of drug resistant food-borne infections.
Pomegranate rind has been found to inhibit numerous pathogens, mostly attributed to its tannin fraction. The present study was conducted to investigate the quorum sensing (QS) inhibition effect of tannin-rich fraction from pomegranate rind (TFPR) by using an indicator strain Chromobacterium violaceum. Meanwhile, its effect on biofilm formation and motility of Escherichia coli was evaluated. It was shown that TFPR inhibited QS-regulated violacein pigment production. Biofilm formation and motility of E. coli were also hindered by TFPR. Transcriptional analysis further showed that TFPR repressed expressions of curli genes (csgB and csgD) and various motility genes (fimA, fimH, flhD, motB, qseB, and qseC). Our findings indicated that TFPR has potential application for controlling E. coli contaminations or biofilms in the food industry.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.