Effect of localized electrochemical pH and temperature synergistic modification on the structural and antibacterial properties of pectin/polyvinyl alcohol/zinc oxide nanorod films.

Two low-methoxy pectins (LMPs) were obtained by local electrochemical pH modification using an H-type double-layer water bath sealed electrochemical cell at the voltage of 180 V for 3 h. The weight-average molecular weight (Mw) of citrus peel pectin (CPP) prepared in the anodic part at room temperature (CPP-A5/RT) and in the cathodic part at 5 °C (CPP-C5/RT) were 346 kDa and 328 kDa, respectively, and the degrees of methylation (DM) were 36.8 % and 11.9 %. Moreover, the second-order kinetic model was most appropriate for the degradation processes, as free radicals were generated in the anodic part and ß-elimination occurred in the cathodic part. Subsequently, CPP-A5/RT and CPP-C5/RT were utilized to fabricate food packaging film blending with polyvinyl alcohol (PVA), bcZnO (ZnO coupled with bentonite and colophony) nanorods, and Ca2+ ions by casting method. Then the prepared films were studied for their ability to maintain the freshness of strawberries. The addition of Ca2+ ions and bcZnO nanorods increased the thickness, water contact angle (WCA), and mechanical properties of the composite films, while decreased water vapor permeability (WVP). Therefore, the CPP-based films, supplemented with bcZnO nanorods and crosslinked with Ca2+ ions by "egg-box" model, can serve as an antibacterial food packaging material for food preservation.

Natural Aldehyde-Chitosan Schiff Base: Fabrication, pH-Responsive Properties, and Vegetable Preservation.

The aim of the present work was to fabricate Schiff base compounds between chitosan and aldehydes and use the resultant aldehyde-chitosan Schiff bases for broccoli preservation. Using an element analyzer, the degree of substitution was calculated as 68.27-94.65%. The aldehyde-chitosan Schiff bases showed acidic sensitivity to rapid hydrolysis for releasing aldehyde at a buffer solution of pH 4-6, in which more than 39% of the aldehydes were released within 10 h. The release of aldehydes endows the aldehyde-chitosan Schiff bases with a better antibacterial activity at pH 5 than at pH 7. In a simulated CO2 (5-15%) atmosphere with high humidity (92%), the hydrolysis of imine bonds (C=N) was triggered and continuously released aldehyde, even without direct contact with the aqueous phase. The application of aldehyde-chitosan Schiff bases significantly extended the shelf life of broccoli from 4 d to 5-7 d and decreased the weight loss of broccoli during storage. In summary, the fabrication of aldehyde-chitosan Schiff bases and the strategy of using pH-response imine bond (C=N) hydrolysis (thus releasing aldehyde to kill microorganisms) were feasible for use in developing EO-incorporated intelligent food packages for vegetable preservation.

Effect of different NaCl concentrations on the structure-function relationship of citrus peel pectins modified by electrochemistry.

In this study, the modified citrus peel pectins (CPPs) were successfully produced by electrochemistry with varying NaCl concentrations of 0, 0.01 % and 0.1 % w/v using an H-type cell at 40 mA current. After 4 h, the pH and oxidation-reduction potential (ORP) of oxidized CPP solution in the anodic region were 2.00- 2.52 and 371.17- 564.45 mV, respectively, due to the electrolysis of water, whereas those of reduced CPP solution in cathodic region were 9.46- 10.84 and - 202.77 âˆ¼ -230.57 mV. The modified CPPs in the anodic region (A-0, A-0.01, and A-0.1) exhibited significantly higher weight-average molecular weights and methyl esterification degrees than those in the cathodic region (C-0, C-0.01 and C-0.1). In contrast, the K+, Mg2+, and Ca2+ contents of A-0, A-0.01, and A-0.1 were lower than those of C-0, C-0.01 and C-0.1 due to the electrophoretic migration. Furthermore, the antioxidant activities of A-0 and A-0.01 solutions were stronger than those of the C-0, C-0.01, and C-0.1, while rheological and texture properties of their hydrogels showed contradictory results. Finally, the potential structure-function relationships of CPPs were explored by combining PCA and correlation analysis. Overall, this study introduced a potential approach for pectin purification and functional low-methoxyl pectin manufacturing.

Efflux Pumps and Different Genetic Contexts of tet(X4) Contribute to High Tigecycline Resistance in Escherichia fergusonii from Pigs.

Tigecycline is a last-resort antibiotic for the treatment of infections caused by multidrug-resistant bacteria. The emergence of plasmid-mediated tigecycline resistance genes is posing a serious threat to food safety and human health and has attracted worldwide attention. In this study, we characterized six tigecycline-resistant Escherichia fergusonii strains from porcine nasal swab samples collected from 50 swine farms in China. All the E. fergusonii isolates were highly resistant to tigecycline with minimal inhibitory concentration (MIC) values of 16-32 mg/L, and all contained the tet(X4) gene. In addition, 13-19 multiple resistance genes were identified in these isolates, revealed by whole-genome sequencing analysis. The tet(X4) gene was identified as being located in two different genetic structures, hp-abh-tet(X4)-ISCR2 in five isolates and hp-abh-tet(X4)-ΔISCR2-ISEc57-IS26 in one isolate. The role of efflux pumps in tigecycline resistance was evaluated by using inhibitor carbonyl cyanide 3-chlorophenylhydrazone (CCCP). The MIC values of tigecycline showed a 2- to 4-fold reduction in the presence of CCCP, indicating the involvement of active efflux pumps in tigecycline resistance in E. fergusonii. The tet(X4) gene was found to be transferable to Escherichia coli J53 by conjugation and resulted in the acquisition of tigcycline resistances in the transconjugants. Whole-genome multilocus sequence typing (wgMLST) and phylogenetic analysis showed a close relationship of five isolates originating from different pig farms, suggesting the transmission of tet(X4)-positive E. fergusonii between farms. In conclusion, our findings suggest that E. fergusonii strains in pigs are reservoirs of a transferable tet(X4) gene and provide insights into the tigecycline resistance mechanism as well as the diversity and complexity of the genetic context of tet(X4) in E. fergusonii.

Antimicrobial Activity of Sertraline on Listeria monocytogenes.

We explored the antimicrobial activity of sertraline on Listeria monocytogenes and further investigated the effects of sertraline on biofilm formation and the virulence gene expression of L. monocytogenes. The minimum inhibitory concentration and minimum bactericidal concentration for sertraline against L. monocytogenes were in the range of 16-32 µg/mL and 64 µg/mL, respectively. Sertraline-dependent damage of the cell membrane and a decrease in intracellular ATP and pHin in L. monocytogenes were observed. In addition, sertraline reduced the biofilm formation efficiency of the L. monocytogenes strains. Importantly, low concentrations (0.1 µg/mL and 1 µg/mL) of sertraline significantly down-regulated the expression levels of various L. monocytogens virulence genes (prfA, actA, degU, flaA, sigB, ltrC and sufS). These results collectively suggest a role of sertraline for the control of L. monocytogenes in the food industry.

Characterization of extended-spectrum cephalosporins and fluoroquinolone resistance of a Salmonella enterica serovar Thompson isolate from ready-to-eat pork product in China.

Salmonella is a leading cause of foodborne illness worldwide and is a common concern in food safety. Salmonella enterica displaying resistance to extended-spectrum cephalosporins (ESCs) and fluoroquinolone (FQs) has been deemed a high-priority pathogen by the World Health Organization. Co-resistance to ESCs and FQs has been reported in S. enterica serovar Thompson (S. Thompson). However, the genetic context of ESCs and FQs resistance genes in S. Thompson lacks sufficient characterization. In this study, we characterized a multi-drug resistant (MDR) S. Thompson isolate recovered from a retail ready-to-eat (RTE) pork product in China. Short- and long-read sequencing (HiSeq and MinION) of the genome identified the presence of bla CMY-2, qnrS1, and qepA8, along with 11 additional acquired antimicrobial resistance genes, residing on a 152,940 bp IncA/C plasmid. Specifically, the bla CMY-2, qnrS1, and qepA8 genes were located in insertion sequences (ISs) and integron mediated mobile genetic structure, sugE-blc-bla CMY-2-ISEc9, IS26-orf6-qnrS1-orf5-ISKpn19, and intl1-qepA8-orf10-IS91-orf1-dfrA12-orf11-aadA2-qacEΔ1-sul1, respectively. Each gene was identified in various bacteria species, indicating their high transfer ability. The plasmid was found to be transferable to Escherichia coli J53 by conjugation and resulted in the acquiring of multiple resistances in the transconjugants. The plasmid is closely related to plasmids from two human S. Thompson strains isolated in different regions and years in China. Moreover, core-genome Multi Locus Sequence Typing (cgMLST) and phylogenetic analysis based on global 1,868 S. Saintpaul isolates showed that the S. Thompson isolate was highly epidemiologically linked to a human isolate in China. Our findings suggest that Chinese RTE pork products are a possible source of human pathogenic ESCs and FQs co-resistant S. Thompson. Furthermore, the results underline the important role of conjugative plasmids in acquiring and transmission of ESCs and FQs resistance in S. Thompson isolates, which need continuous investigation.

Phenyllactic acid application to control Listeria monocytogenes biofilms and its growth in milk and spiced beef.

Listeria monocytogenes, as a food-associated pathogen, is able to develop biofilms on different surfaces of food contact, which seriously threatens food safety. Phenyllactic acid (PLA) exhibits excellent inhibitory effects on many bacterial strains including L. monocytogenes. Our study aimed to investigate effects of PLA on L. monocytogenes biofilms and its growth in milk and on spiced beef. Biofilm biomass was measured by the microplate method and biofilm structure was observed by electron microscopy. Growth of L. monocytogenes in food samples was determined by colony counting. Results from the agar dilution method demonstrated that L. monocytogenes 10403S had a PLA minimum inhibitory concentration (MIC) value of 6 mg/ml. Sub-inhibitory concentrations of PLA could inhibit biofilm formation by reducing the secretion of exopolysaccharides and extracellular proteins in L. monocytogenes. PLA at concentrations above 1/2MIC could destroy mature biofilms of L. monocytogenes by decreasing the exopolysaccharides and extracellular proteins in the biofilm framework. Both swimming and swarming motilities of L. monocytogenes were inhibited by PLA. The hemolytic activity of L. monocytogenes was inactivated by PLA. However, the capacity to attach and invade Caco-2 cells was not affected by PLA. The results displayed that PLA had no effect on the expression of genes associated with motility, but reduced the expression level of the hly gene encoding Listeria hemolysin. When added to ultra-high temperature (UHT) whole and pasteurized milk, PLA at 3 mg/ml inhibited L. monocytogenes growth through 14 days of storage at 4 °C. PLA at concentrations ≥3 mg/ml significantly reduced L. monocytogenes counts on spiced beef samples during storage. PLA has potential as an alternative antimicrobial to control L. monocytogenes contamination and its biofilms in food industry.

Enhancing the Emulsification and Photostability Properties of Pectin from Different Sources Using Genipin Crosslinking Technique.

Pectin is a potential polysaccharide-based emulsifier, but the stabilized emulsions suffer from insufficient emulsion stability. Therefore, modification is needed to enhance its emulsification performance to cater to practical applications. The genipin-crosslinking strategy was used in this work to modify pectin with different sources and extraction conditions. Chemical composition analysis, molecular weight (Mw), and radius of gyration (Rg) measurement revealed that sugar beet pectin (SBP) has a more compact and flexible conformation than commercial citrus pectin (CP) and apple pectin (AP), indicated by the significantly (p < 0.05) larger Mw/Rg of SBP (18.1−11.3 kg/mol/nm) than CP (8.3 kg/mol/nm) and AP (8.0 kg/mol/nm). Crosslinking modification significantly increased the Mw, radius of gyration, and viscosity. This significantly (p < 0.05) improved the emulsifying stability (a smaller increase in droplets size) by the contribution of both thicker adsorbed hydrated layers at the oil-water interface with a stronger steric-hindrance effect and larger viscosity effect to slow down droplet collision. The formation of a blue-black substance from crosslinking reaction was able to block the UV radiation, which significantly improved the photostability of ß-carotene-loaded emulsions. Altogether, genipin-crosslinking is feasible to modify pectin of different sources to enhance the emulsion stability and for use as a vehicle for delivering bioactive compounds.

Genetic context of bla CTX-M-55 and qnrS1 genes in a foodborne Salmonella enterica serotype Saintpaul isolate from China.

Salmonella enterica resistant to fluoroquinolones (FQs) and extended-spectrum cephalosporins (ESCs) has been deemed a high-priority pathogen by the WHO. Salmonella enterica serovar Saintpaul (S. Saintpaul) co-resistant to ESCs and FQs and harboring corresponding resistance genes (bla CTX-M-55 and qnrS1) have been previously reported. However, they have not been reported in China. Moreover, the genetic context and transferability of ESCs and FQs resistance genes in S. Saintpaul remain obscure. This study is the first study to characterize a multidrug-resistant (MDR) S. Saintpaul isolate (16Sal016) harboring plasmid-mediated bla CTX-M-55 and qnrS1 genes recovered from weever fish in China. The whole genome short- and long-read sequencing results identified the presence of 15 acquired antibiotic resistance genes encoding resistance to nine classes of antibiotics, as well as abundant mobile genetic elements residing on a 259,529 bp IncHI2 plasmid. The bla CTX-M-55 and qnrS1 genes were located in a 12,865 bp region, IS26-orf-orf-ISKpn19-qnrS1-IS3-Tn3-orf-bla CTX-M-55-ISEc9-orf-IS26. Similar structures have been identified in various bacterial species, indicating a high transferability of bla CTX-M-55 and qnrS1 genes within this gene cluster. The plasmid was found to be transferable to Escherichia coli (E. coli) J53 by conjugation and resulted in the acquisition of multiple resistances by the transconjugants. Genome sequence comparisons by core genome multilocus sequence typing (cgMLST) based on global 2,947 S. Saintpaul isolates indicated that strain 16Sal016 was epidemiologically linked with an isolate from the United Kingdom (UK). Our findings suggest that plasmids and IS26-mediated mobile genetic elements are carriers of bla CTX-M-55 and qnrS1 genes in S. Saintpaul, and highlight their potential transmission, which needs continuous investigations.

Genomic Characterization of mcr-1-Carrying Foodborne Salmonella enterica serovar Typhimurium and Identification of a Transferable Plasmid Carrying mcr-1, bla CTX-M-14 , qnrS2, and oqxAB Genes From Ready-to-Eat Pork Product in China.

Salmonella enterica resistant to colistin, third-generation cephalosporins (3GCs), and fluoroquinolones (FQs) has been deemed a high-priority pathogen by the World Health Organization (WHO). The objective of this study was to characterize 11 mcr-1-harboring Salmonella enterica serovar Typhimurium isolates from raw pork and ready-to-eat (RTE) pork products in Guangzhou, China. All isolates were multi-drug resistant and contained 6-24 antibiotic-resistant genes. The mcr-1 gene was localized in the most conserved structure (mcr-1-orf ) in eight isolates and in mobile structure (ISApl1-mcr-1-orf ) in three isolates. One raw pork isolate SH16SF0850, co-harbored mcr-1, bla CTX-M-14, and oqxAB genes. One isolate 17Sal008 carried mcr-1, bla CTX-M-14, qnrS2, and oqxAB genes located on a 298,622 bp IncHI2 plasmid pSal008, which was obtained from an RTE pork product for the first time. The pSal008 was closely related to a plasmid in an S. typhimurium isolate from a 1-year-old diarrheal outpatient in China and was found to be transferable to Escherichia coli J53 by conjugation. Genome sequence comparisons by core-genome Multi Locus Sequence Typing (cgMLST) based on all S. typhimurium isolates from China inferred highly probably epidemiological links between selected pork isolates and no possible epidemiologically links between RTE pork isolate 17Sal008 and other isolates. Our findings indicate that raw pork and pork products are potential reservoirs of mcr-1-harboring S. typhimurium and highlight the necessity for continuous monitoring of colistin, 3GCs, and FQs resistant S. typhimurium from different origins.

Engineering a CRISPR interference system targeting AcrAB-TolC efflux pump to prevent multidrug resistance development in Escherichia coli.

OBJECTIVES: We engineered a CRISPR interference (CRISPRi) system targeting the AcrAB-TolC efflux pump to prevent MDR development in Escherichia coli. METHODS: Nine specific single-guide RNAs (sgRNAs) were designed to target the components of the AcrAB-TolC efflux pump, namely AcrA, AcrB and TolC. A total of thirteen CRISPRi recombinant plasmids were constructed with single or clustered sgRNAs. The transcriptional levels of the target genes, MICs of multiple antibiotics and biofilm formation in each CRISPRi strain were tested. RESULTS: The CRISPRi system expressing sgRNA clusters targeting acrB and tolC simultaneously exhibited the highest inhibitory effect on AcrAB-TolC efflux pump activity in E. coli HB101, with 78.3%, 90.0% and 65.4% inhibition rates on the transcriptional levels of acrA, acrB and tolC, respectively. The CRISPRi system resulted in ∼2-, ∼8- and 16-fold increased susceptibility to rifampicin, erythromycin and tetracycline, respectively. In addition, the constructed CRISPRi system reduced biofilm formation with inhibition rates in the range of 11.2% to 58.2%. CONCLUSIONS: To the best of our knowledge, this is the first report on the construction of an inducible CRISPRi system targeting the AcrAB-TolC efflux pump to prevent MDR development in E. coli. This study provides insights for future regulation and manipulation of AcrAB-TolC activity and bacterial MDR by a CRISPRi system.

Tannic Acid-Aminated Sugar Beet Pectin Nanoparticles as a Stabilizer of High-Internal-Phase Pickering Emulsions.

Pickering stabilizers with additional antioxidant, photostabilizing, and metal-chelating properties are suitable for structuring multifunctional Pickering emulsion systems. Tannic acid (TA) is a potential material which when adsorbed onto the interface may impart antioxidant, UV-light-shielding, and chelating properties to Pickering stabilizers. Herein, we report a type of TA polyelectrolyte nanoparticles (NPs) fabricated following a complexation between TA and aminated sugar beet pectin (SBP-NH2). This study is geared toward investigating the performance of TA/SBP-NH2 NPs in stabilizing Pickering emulsions and protecting ß-carotene from degradation. TA/SBP-NH2 NPs formed under optimum conditions had a mean diameter of 82 nm with a sphere-like shape. Because of their favorable surface wettability (91.2°), TA/SBP-NH2 NPs promoted formation of the low-, medium-, and high-internal-phase Pickering emulsions (HIPEs) in an oil volume fraction (φ)-dependent manner; the TA/SBP-NH2 NP-stabilized HIPE demonstrated viscoelastic properties increasing with the increasing concentration (c) of nanoparticles. Due to the excellent storage stability and UV light-absorbing capacity, the photostability of ß-carotene was significantly improved by a TA/SBP-NH2 NP-stabilized HIPE (φ = 0.75; c = 3 mg/mL). Altogether, this study highlights that TA/SBP-NH2 NPs have potential applications in structuring Pickering emulsions with improved protective effects on loaded lipophilic compounds.

Exploring the resistome, virulome, mobilome and microbiome along pork production chain using metagenomics.

In order to understand and minimize microbial contaminants spread from animal to raw pork products, we explored the diversity of antibiotic resistance genes (ARGs), virulence factors (VFs), mobile genetic elements (MGEs) and the bacterial community composition in feces of pigs, processing areas as well as the end pork products in a large-scale pig slaughterhouse in China using metagenomics. The abundance and diversity of microbial community was higher in arrival and slaughtering room area and decreased sharply in the end pork products. Furthermore, the relative abundance of some clinically relevant pathogens and opportunity pathogens were greater in the end pork products and cutter samples. We identified 1412 subtypes of ARGs related to 30 antibiotic classes, in which ARGs related to multidrug resistance and ß-lactamase were dominant. Resistance determinants to clinically critical important antibiotics, including sequences related to mcr, optrA, poxtA, tetX and ß-lactamase genes (i.e. blaOXA, blaVIM, blaIMP, blaGES, blaNDM, blaKPC and blaSME) were detected. More than 42 general virulence features, mainly adherence, secretion system, iron uptake, toxin, antiphagocytosis and immune evasion, were identified. A total of 1922 types of MGEs, mainly plasmids were observed. Most of the ARGs are predicted to be associated with MGEs. The prevalence of ARGs, VFs and MGEs decreased over subsequential processing steps. Most of the remaining ARGs, VFs and MGEs in end pork products were also present on other samples, indicating the flow of these genes through the production line. These results broaden our understanding of the global ARGs, VFs and MGEs diversity along the pork production chain, with the suggestion of implementing improved control measures to reduce the risk of spread of pathogenic bacteria and their associated resistome, virulome and mobilome from animal to the food chain and the surrounding environment.

Short- and long-read metagenomics insight into the genetic contexts and hosts of mobile antibiotic resistome in Chinese swine farms.

Antibiotic resistance genes (ARGs) are emerging environmental contaminants posing a threat to public health. Intensive swine farms are recognized as hotspots for antibiotic resistance genes (ARGs). However, antibiotic resistome and their genetic contexts, hosts, and transferability in Chinese swine farms remain largely unexplored. Here, we used Illumina and Oxford Nanopore metagenomics sequencing to investigate the antibiotic resistome context of 14 distantly located large-scale (10,000 animals per year) commercial swine farms in China. We identified high abundant and diverse ARGs (609,966.8 with 1433 types, belonging to 38 different antibiotic classes) in all samples, including those encoding resistance to clinically critical important antibiotics (such as mcr, tetX, optrA, poxtA, qnr and blaCTX-M). About 75% of the ARGs detected were carried by mobile genetic elements (mainly plasmids), suggesting their high transmission potential into receiving environments. Host-tracking analysis identified Clostridiales, Faecalibacterium prausnitzii and Escherichia coli as the predominant bacterial hosts of mobile ARGs. Notably, genome binning generated 246 high-completeness draft genomes. Genetic context analysis of the multiple resistant (MDR) genes in binned genomes showed the involvement of insertion sequences (ISs), integron and SGI2 genomic island, implying their importance role in promoting the development of MDR bacteria. Overall, these findings substantially expand our current knowledge of mobile antibiotic resistome in Chinese swine farms, and suggest reasonable management of animal wastes in swine farms to reduce the dissemination of antibiotic resistance to the environment.

Antimicrobial activity of cyanidin-3-O-glucoside-lauric acid ester against Staphylococcus aureus and Escherichia coli.

Enzymatic acylation of anthocyanin with fatty acid improves its lipophilic solubility and application potential. Nevertheless, evaluation of functional properties of product is premise for application. This study investigated the antimicrobial potential and the underlying mechanisms of an acylated anthocyanin, namely, cyanidin-3-O-glucoside-lauric acid ester (C3G-LA), to provide guidelines for its application. C3G-LA exhibited outstanding antibacterial activity against Staphylococcus aureus [minimum inhibitory concentration (MIC) = 0.3125 mg/mL] and modest activity against Escherichia coli (MIC = 5 mg/mL). Moreover, C3G-LA manifested bactericide ability against S. aureus at 0.625 mg/mL. Decreases in membrane integrity (by 96% and 92% at MIC in S. aureus and E. coli, respectively), intracellular ATP concentration (by 96% and 92%) and intracellular pH (by 11% and 9%) and changes in cellular morphology altogether indicated the dysfunction of cell membrane under C3G-LA treatment. These findings demonstrated that C3G-LA could be adopted as an alternative food preservative against foodborne pathogens.

Corrigendum: First Report of a Foodborne Salmonella enterica Serovar Gloucester (4:i:l,w) ST34 Strain Harboring bla CTX-M-55 and qnrS Genes Located in IS26-Mediated Composite Transposon.

[This corrects the article DOI: 10.3389/fmicb.2021.646101.].

First report of two foodborne Salmonella enterica subsp. enterica serovar Bovismorbificans isolates carrying a novel mega-plasmid harboring blaDHA-1 and qnrB4 genes.

Salmonella enterica displaying resistance to extended-spectrum cephalosporins and fluoroquinolone (FQs) has been deemed a high-priority pathogen by the World Health Organization (WHO). While CTX-M type acquired ß-lactamases have been detected in S. enterica serovar Bovismorbificans, DHA enzymes have been rarely reported in S. Bovismorbificans. In this study, we here report for the first time the isolation of two multi-drug resistant (MDR) S. Bovismorbificans strains co-harboring plasmid-encoded AmpC (pAmpC) ß-lactamase gene (blaDHA-1) and qnrB gene, 16Sal017 isolated from a chicken meat sample and 16Sal018 from a grass carp fish sample, collected from retail markets in Guangzhou, China. The blaDHA-1 and qnrB genes in these two strains were both located on the same novel 217,773 bp IncHI2 plasmid belonged to ST2. The plasmid contained 16 additional acquired antimicrobial resistance genes encoding resistance to eight antibiotic classes and quaternary ammonium compound. Besides, 16Sal017 contained an additional 10,124 bp Col (pHAD28)-like plasmid harboring qnrS1. The blaDHA-1 and qnrB4 genes were located in an 18,198 bp region, sul1-qacEΔ1-ampR-blaDHA-1-pspABCDF-qnrB4-sapABC-IS91-sul1-qacEΔ1, which has been identified in various bacteria species, indicating the high transfer ability of blaDHA-1 and qnrB4 genes within this gene cluster. The IncHI2 plasmid was found to be transferable to Escherichia coli J53 by conjugation and resulted in the acquiring of multiple resistance in the transconjugants. Genome sequence comparisons by cgMLST and MAUVE alignment indicated 16Sal017 and 16Sal018 are highly similar and are not epidemiologically linked with strains from other sources and countries. Our findings suggest S. Bovismorbificans as a new host for conjugative mega-plasmid harboring blaDHA-1 and qnrB4 genes, and highlight the potential transmission opportunity of these S. Bovismorbificans clones through the food chain, which need continuous investigation.

First Report of a Foodborne Salmonella enterica Serovar Gloucester (4:i:l,w) ST34 Strain Harboring bla CTX-M- 55 and qnrS Genes Located in IS26-Mediated Composite Transposon.

Extended-spectrum ß-lactamases (ESBLs) production and (fluoro)quinolone (FQ) resistance among Salmonella pose a public health threat. The objective of this study was the phenotypic and genotypic characterization of an ESBL-producing and nalidixic acid-resistant Salmonella enterica serovar Gloucester isolate (serotype 4:i:l,w) of sequence type 34 (ST34) from ready-to-eat (RTE) meat products in China. Whole-genome short and long read sequencing (HiSeq and MinION) results showed that it contained bla CTX-M- 55, qnrS1, and tetB genes, with bla CTX-M- 55 and qnrS1 located in chromosomal IS26-mediated composite transposon (IS26-qnrS1-IS3-Tn3-orf-bla CTX-M- 55-ISEcp1-IS26). The same genetic structure was found in the chromosome of S. enterica subsp. enterica serovar Typhimurium strain and in several plasmids of Escherichia coli, indicating that the IS26-mediated composite transposon in the chromosome of S. Gloucester may originate from plasmids of E. coli and possess the ability to disseminate to Salmonella and other bacterial species. Besides, the structural unit qnrS1-IS3-Tn3-orf-bla CTX-M- 55 was also observed to be linked with ISKpn19 in both the chromosomes and plasmids of various bacteria species, highlighting the contribution of the insertion sequences (IS26 and ISKpn19) to the co-dissemination of bla CTX-M- 55 and qnrS1. To our knowledge, this is the first description of chromosomal bla CTX-M- 55 and qnrS in S. Gloucester from RTE meat products. Our work expands the host range and provides additional evidence of the co-transfer of bla CTX-M- 55 and qnrS1 among different species of Salmonella through the food chain.

Preparation and characterization of chitosan-based edible active films incorporated with Sargassum pallidum polysaccharides by ultrasound treatment.

In this study, Sargassum pallidum polysaccharides (SPPs) were incorporated into chitosan (CH) to develop a novel edible active film (CH/SPPs-US) via ultrasonication. The mechanical, water vapor permeability, surface morphology, crystallinity, antioxidant, and fruit preservation properties of CH/SPPs-US films prepared under sequences of matrix ratios and ultrasound treatment were investigated. The results revealed that the addition of SPPs combined with ultrasonic treatment could significantly enhance the transparency, elongation and tensile strength of the films whereas the water vapor permeability was decreased. Tensile strength and elongation at break of the C2/SP1.2-US film were 12.07 N and 54.18%, respectively, which were significantly higher than those for CH film. Meanwhile, the water vapor permeability value of C2/SP1.2-US was reduced by as high as 40.2% compared with that of chitosan film. In addition, antioxidant effect evaluation showed that the CH-based films added with SPPs exhibited better antioxidant activity than CH film, and ultrasonic treatment could further strengthen the antioxidant activity of the film. The CH/SPPs-US films could effectively extend the shelf life and inhibit the deterioration of the strawberry at room temperature (25 ± 1 °C) and 70% ± 5% relative humidity for 7 days. These results indicated that the CH/SPPs edible films via ultrasonication could be developed as edible packaging films for the preservation of fresh fruits.

Genipin crosslinked gum arabic: Synthesis, characterization, and emulsification properties.

Although recognized as a "gold standard" emulsifier in food industry, gum arabic (GA) is characterized by high dosage consumption and inconsistent emulsification performance. This work aimed to solve the above shortcomings by crosslinking GA with genipin. The resulting genipin-crosslinked GA (G-GA) had larger molecular weight (1596 kg/mol) and mean radius of gyration (64.9 nm) than the control GA (denoted as C-GA; 529 kg/mol and 19.2 nm), featuring a more compact conformation. More importantly, the proportion of the arabinogalactan protein (AGP) component of G-GA increased, endowing G-GA with enhanced emulsifying stability. The dosage required for emulsification were less for G-GA (7.5 %) than C-GA (15 %) in 20 % oil emulsion. The G-GA-stabilized emulsions sterilized (110 °C for 30 min) or treated at 60 °C for 10 d were more stable. Overall, this study demonstrates that genipin crosslinking is a suitable strategy providing GA with enhanced emulsification properties while saving the emulsifier dosage.