The sensitive detection of foodborne pathogens is of great significance for ensuring food safety and quality. Herein, on the basis of methylene blue-embedded zirconium based organic framework ( [email protected] ) as the remarkable capture carrier and signal indicator, with the Al 3+ -assisted the fluorescent signal response, we developed a label-free and dual-signal lateral flow immunochromatographic assay (LDLFIA) for sensitive detection of Escherichia coli ( E. coli ) O157:H7. The [email protected] sensing carrier without monoclonal antibodies (mAbs) was manufactured, which adhered to bacteria to form the [email protected] E. coli O157:H7 conjugate, resulting in visible blue band. Then the fluorescent response of the OH-rich [email protected] was excited by introducing Al 3+ , arising from capturing of Al 3+ by -OH through coordination and electrostatic affinity, thus generating a green fluorescent band. Impressively, a smartphone-based portable reading system was developed that can reflect the test results of [email protected] immediately. Under optimum conditions, [email protected] can complete colorimetric and fluorescent mode detection within 90 min, with a detection sensitivity of 10 3 CFU/mL, which were 100 times lower than traditional gold nanoparticles-based LFIA and polymerase chain reaction (PCR). Moreover, the feasibility of the method was further evaluated by the determination of E. coli O157: H7 in drinking water and cabbage with average recoveries of 85.1-123.0%.
In this study, sugarcane bagasse (SB) was pretreated with combination pretreatment (e.g., sequential KOH extraction and ionic liquid soaking, sequential KOH extraction and Fenton soaking, or sequential KOH extraction and glycerol soaking). After the enzymatic hydrolysis of pretreated SBs, it was found that all these three concentrated hydrolyzates could be used for the asymmetric bioreduction of ethyl 4-chloro-3-oxobutanoate (COBE) into ethyl ( S )-4-chloro-3-hydroxybutanoate [( S )-CHBE]. Compared with glucose, arabinose and cellobiose couldn’t promote the initial reaction rate, and xylose could increase the intracellular NADH content. Moreover, it was the first report that hydrolyzates could be used for the effective biosynthesis of ( S )-CHBE (∼500 g/L; 98.0% yield) from 3000 COBE by whole cells of Escherichia coli CCZU-K14 in the presence of β-CD (0.4 mol β-CD/mol COBE), l -glutamine (200 mM) and glycine (500 mM). In conclusion, it is a new alternative to utilize bioresource for the synthesis of key chiral intermediate ( S )-CHBE.
Background The emergence of carbapenem and colistin co-resistant Escherichia coli poses a huge challenge to infection control. The purpose of this study was to clarify the mechanism of the carbapenems and colistin co-resistance in E. coli strains.Methods Antimicrobial susceptibility test was carried out by agar dilution methods and colistin resistance was confirmed by broth microdilution methods. Whole genome sequencing was carried out, and resistance genes, sequence types and virulence genes of carbapenems and colistin co-resistance E. coli isolates were analyzed.Results The results showed that among the 176 carbapenem-resistant Enterobacteriaceae strains, 5 multidrug resistant E. coli strains exhibiting coresistance to carbapenem and colistin. The main mechanism of 5 E. coli strains in this study was generating carbapenem. Four E. coli strains were mcr-positive, while one mcr-negative strain had a new MgrB mutation. The blaNDM-5, blaCTX-M-65, blaOXA-10, blaTEM-1 and mcr-1.1 genes were simultaneously detected in E. coli 20IR1127 strain belonging to ST156 lineage. Other antimicrobial resistance genes encoding aminoglycosides-, sulfonamide-, chloramphenicol-, tetracyclines- and macrolides resistance were also detected.Conclusion The main mechanisms of carbapenem and colistin resistance were encoded by blaNDM and mcr1.1, meanwhile mgrB mutations also contribute to colistin resistance. To our knowledge, this study is the first to report of E. coli ST156 strain in which the blaNDM-5, blaCTX-M-65, blaOXA-10, blaTEM-1 and mcr1.1 genes coexist. In addition, there is also an E. coli ST457 strain, which carries blaTEM-1, blaNDM-9, blaCTX-M-199 and is positive for mcr1.1 gene.
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