Synchronous filtering method for improving the optical signal-to-noise ratio of a tunable laser based on the Fabry-Pérot interferometer.

Optical measurements are closely related to the optical signal-to-noise ratio (OSNR) of the laser, which can be improved using a tunable optical filter (TOF) to suppress frequency noise. For an external-cavity tunable laser with a tuning range larger than the TOF bandwidth, the wavelength at the center of the TOF passband must be varied based on the laser tuning. This study proposes a tunable-laser OSNR-enhancement method based on the Fabry-Pérot (FP) interferometer. The FP signal contains the wavelength information of the swept laser, which can be used to determine the real-time driving voltage of the TOF. Notably, the laser needs to be continuously tunable without mode hopping, and the free spectral range of the FP interferometer must be smaller than the TOF bandwidth.

Biocatalysis in Drug Design: Engineered Reductive Aminases (RedAms) Are Used to Access Chiral Building Blocks with Multiple Stereocenters.

Novel building blocks are in constant demand during the search for innovative bioactive small molecule therapeutics by enabling the construction of structure-activity-property-toxicology relationships. Complex chiral molecules containing multiple stereocenters are an important component in compound library expansion but can be difficult to access by traditional organic synthesis. Herein, we report a biocatalytic process to access a specific diastereomer of a chiral amine building block used in drug discovery. A reductive aminase (RedAm) was engineered following a structure-guided mutagenesis strategy to produce the desired isomer. The engineered RedAm (IR-09 W204R) was able to generate the (S,S,S)-isomer 3 in 45% conversion and 95% ee from the racemic ketone 2. Subsequent palladium-catalyzed deallylation of 3 yielded the target primary amine 4 in a 73% yield. This engineered biocatalyst was used at preparative scale and represents a potential starting point for further engineering and process development.

Markedly Increasing Antibiotic Resistance and Dual Treatment of Neisseria gonorrhoeae Isolates in Guangdong, China, from 2013 to 2020.

The emergence of multidrug resistance in Neisseria gonorrhoeae is concerning, especially the cooccurrence of azithromycin resistance and decreased susceptibility to extended-spectrum cephalosporin. This study aimed to confirm the antibiotic resistance trends and provide a solution for N. gonorrhoeae treatment in Guangdong, China. A total of 5,808 strains were collected for assessment of antibiotic MICs. High resistance to penicillin (53.80 to 82%), tetracycline (88.30 to 100%), ciprofloxacin (96 to 99.8%), cefixime (6.81 to 46%), and azithromycin (8.60 to 20.03%) was observed. Remarkably, spectinomycin and ceftriaxone seemed to be the effective choices, with resistance rates of 0 to 7.63% and 2.00 to 16.18%, respectively. Moreover, the rates of azithromycin resistance combined with decreased susceptibility to ceftriaxone and cefixime reached 9.28% and 8.64%, respectively. Furthermore, genotyping identified NG-STAR-ST501, NG-MAST-ST2268, and MLST-ST7363 as the sequence types among representative multidrug-resistant isolates. Evolutionary analysis showed that FC428-related clones have spread to Guangdong, China, which might be a cause of the rapid increase in extended-spectrum cephalosporin resistance currently. Among these strains, the prevalence of N. gonorrhoeae was extremely high, and single-dose ceftriaxone treatment might be a challenge in the future. To partially relieve the treatment pressure, a susceptibility test for susceptibility to azithromycin plus extended-spectrum cephalosporin dual therapy was performed. The results showed that all the representative isolates could be effectively killed with the coadministration of less than 1 mg/liter azithromycin and 0.125 mg/liter extended-spectrum cephalosporin, with a synergistic effect according to a fractional inhibitory concentration (FIC) of <0.5. In conclusion, dual therapy might be a powerful measure to treat refractory N. gonorrhoeae in the context of increasing antibiotic resistance in Guangdong, China.

Conformational Dynamics, Intramolecular Domain Conformation Signaling, and Activation of Apo-FimD Revealed by Single-Molecule Fluorescence Resonance Energy Transfer Studies.

The chaperone-usher secretion pathway is a conserved bacterial protein secretion system dedicated to the biogenesis of adhesive fibers. Usher, a multidomain-containing outer membrane protein, plays a central role in this process by acting as a molecular machine that recruits different chaperone-subunit complexes, catalyzes subunit polymerization, and forms a channel for secretion of the assembled subunits. While recent crystal structural studies have greatly advanced our understanding of the structure and function of ushers, the overall architecture of the full-length apo-usher, the molecular events that dictate conformational changes in usher during pilus biogenesis, and its activation by the specific chaperone-adhesin complex remain largely elusive. Using single-molecule fluorescence resonance energy transfer studies, we found that the substrate-free usher FimD (apo-FimD) adopts a contracted conformation that is distinct from its substrate-bound states; both the N-terminal domain (NTD) and the C-terminal domain (CTD) of apo-FimD are highly dynamic, and FimD coordinates its domain conformational changes via intramolecular domain conformation signaling. By combining these studies with in vitro photo-cross-linking studies, we further show that only the chaperone-bound adhesin (FimC:FimH) can be transferred to the CTD, dislocates the plug domain, and triggers conformational changes in the remaining FimD domains. Taken together, these studies delineate an overall architecture of the full-length apo-FimD, provide detailed mechanic insight into the activation of apo-FimD, and explain why FimD could adjust its conformational states to perform multiple functions in each cycle of pilus subunit addition and ensure that pilus assembly proceeds progressively in a cellular energy-free environment.

Different structures of berberine and five other protoberberine alkaloids that affect P-glycoprotein-mediated efflux capacity.

Berberine, berberrubine, thalifendine, demethyleneberberine, jatrorrhizine, and columbamine are six natural protoberberine alkaloid (PA) compounds that display extensive pharmacological properties and share the same protoberberine molecular skeleton with only slight substitution differences. The oral delivery of most PAs is hindered by their poor bioavailability, which is largely caused by P-glycoprotein (P-gp)-mediated drug efflux. Meanwhile, P-gp undergoes large-scale conformational changes (from an inward-facing to an outward-facing state) when transporting substrates, and these changes might strongly affect the P-gp-binding specificity. To confirm whether these six compounds are substrates of P-gp, to investigate the differences in efflux capacity caused by their trivial structural differences and to reveal the key to increasing their binding affinity to P-gp, we conducted a series of in vivo, in vitro, and in silico assays. Here, we first confirmed that all six compounds were substrates of P-gp by comparing the drug concentrations in wild-type and P-gp-knockout mice in vivo. The efflux capacity (net efflux) ranked as berberrubine > berberine > columbamine ~ jatrorrhizine > thalifendine > demethyleneberberine based on in vitro transport studies in Caco-2 monolayers. Using molecular dynamics simulation and molecular docking techniques, we determined the transport pathways of the six compounds and their binding affinities to P-gp. The results suggested that at the early binding stage, different hydrophobic and electrostatic interactions collectively differentiate the binding affinities of the compounds to P-gp, whereas electrostatic interactions are the main determinant at the late release stage. In addition to hydrophobic interactions, hydrogen bonds play an important role in discriminating the binding affinities.

[Research of pollution-free and precision cultivation system of Chinese herbal medicines].

The issues of disordering production and non-standard pesticide application are common in the production of Chinese herbal medicines. Aimed to above problems, research groups built the pollution-free and precision cultivation system of medicinal plants. This system mainly included the precise site selection of medicinal plants based on the GIS technology, modern omics-assisted breeding, metagenomics guiding the soil complex improvement, and the precise field management based on rational application of fertilizer and comprehensive control of disease. At present, the production and distribution of medicinal plants were performed in the many poor counties of the whole nation. The breeding platform of resistant varieties was built, and certificates of new and well-bred varieties were received, in the base of genetic backgrounds of the original species of medicinal plants. The disease incidences were declined after application of these resistant varieties. Additionally, chemical pesticide consumption of medicinal plants (such as Panax ginseng, P. notoginseng, Salvia miltiorrhiza, P. quinquefolium, Schisandra chinensis, Platycodon grandiflorum and P. grandiflorus etc.) reduced by 20%-80% based on the genetic testing technologies of plant diseases and insect pests and safety evaluation of pollution-free pesticides. The application of pollution-free and precision cultivation system of Chinese herbal medicines achieve significantly social, economic and ecological benefits.

[DNA marker-assisted selection of medicinal plants (â ¢)Evaluation of disease resistance of "Miaoxiang Kangqi 1" --a new cultivar of Panax notoginseng].

DNA marked-assisted selection of medicinal plants accelerated the breeding and promotion of new cultivars, and guaranteed the healthy development of Chinese medicinal materials industry. The first disease-resistant cultivar of notoginseng, namely "Miaoxiang Kangqi 1", served as the object of study. We evaluated the Kangqi's resistance of seeds, seedlings and root against the pathological bacteria (Fusarum oxysporum) of root rot. Compared to the traditional cultivars, the disease index of notoginseng seeds declined by 52.0% after inoculation for seven days; the death rate of seedlings and disease index of root respectively decreased by 72.1% and 62.4% after inoculation for 25 days. Additionally, the growth inhibition ratio of notoginseng seeds and seedlings declined after inoculation. The seeds, seedlings and roots of "Miaoxiang Kangqi 1" showed significantly resistant to root rot. The evaluation of disease-resistance of Kangqi provided the basis for the popularization of new cultivar and guaranteed the favoring conduct of notoginseng pollution-free cultivation.

[DNA marker-assisted selection of medicinal plants (â ) .Breeding research of disease-resistant cultivars of Panax notoginseng].

DNA marker-assisted selection of medicinal plants is based on the DNA polymorphism, selects the DNA sequences related to the phenotypes such as high yields, superior quality, stress-resistance and so on according to the technologies of molecular hybridization, polymerase chain reaction and high-throughput sequencing, and assists the breeding of new cultivars. This study bred the first disease-resistant cultivar of notoginseng "Miaoxiang Kangqi 1" using the technology of DNA marker-assisted selection of medicinal plants and systematic breeding. The disease-resistant cultivar of notoginseng contained 12 special SNPs based on the analysis of Restriction-site Associated DNA Sequencing (RAD-Seq). Among the SNP (record_519688) was related to the root rot-resistant characteristics, which indicated this SNP could serve as genetic markers of disease-resistant cultivars and assist the systematic breeding. Compared to the conventional cultivated cultivars, the incidence rate of root-rot and rust-rot in notoginseng seedlings decreased by 83.6% and 71.8%, respectively. The incidence rate of root-rot respectively declined by 43.6% and 62.9% in notoginseng cultivation for 2 and 3 years compared with those of the conventional cultivated cultivars. Additionally, the potential disease-resistant groups were screened based on the relative SNP, and this model enlarged the target groups and advanced the breeding efficiency. DNA marker-assisted selection of medicinal plants accelerated the breeding and promotion of new cultivars, and guaranteed the healthy development of Chinese medicinal materials industry.

[Analysis of global ecology of Panax notoginseng in suitability and quality].

In this study, the Geographic Information System for Global Medicinal Plants(GMPGIS) was used to assess the global production and ecological adaptation of Panax notoginseng. Based on climate factors and soil types of P. notoginseng from 326 sampling sites, which cover both traditional and current major producing regions, as well as on the results of the ecological similarity computing analysis, we obtained the maximum ecological similarity areas for P. notoginseng worldwide. The results indicated that China was the most suitable ecological and cultivated area globally for P. notoginseng, accounting for more than 70% of the total cultivated area in the world. The United States, Brazil, Portugal, and other 22 countries also had a small amount of potential suitable producing area. China has eight potential suitable producing provinces, including Yunnan, Fujian, Guangxi, Guizhou, etc. The prediction is consistent with the new district of P. notoginseng reported in recent years, which verifies the accuracy of the prediction of GMPGIS. We conducted a literature analysis on resource regeneration and quality ecology on P. notoginseng, and summarized the cultivation, wild tending models, and effects of environmental factors on the quality of P. notoginseng. The results provide scientific basis for selection of P. notoginseng, as well as the introduction, cultivation, and production of P. notoginseng worldwide.

[Contents and the Correlations of the Total Anthocyanins and Saponins of the Vegetative Organs of Panax notoginseng with Purple and Green Aerial Stems at Different Growth Stages].

Objective: To study the accumulation characteristics of total anthocyanins and saponins in the vegetative organ of Panax notoginseng with purple and green aerial stems at different growth stages. Methods: The contents of the total anthocyanins and saponins of the leaves, aerial stems, rhizomes and the adventitious roots of one-, two- and three-year-old Panax notoginseng with purple and green aerial stems were determined by spectrophotometry. Results: From one-year-old to three-year-old Panax notoginseng, the total anthocyanin contents (TACs) of the leaves, aerial stems and all vegetative organs and the percentages of the aerial stems TACs to those of all vegetative organs of purple aerial stemmed Panax notoginseng plants, the percentages of the total saponin contents (TSCs) of the leaves and aerial stems to those of all vegetative organs of the purple and green aerial stemmed plants and the percentages of the leaves TACs to those of vegetative organs of the green aerial stemmed plants all decreased. The TACs of the leaves and all vegetative organs of the green aerial stemmed plants, the TACs of the rhizomes and their adventitious roots, the vegetative organ TSCs and the percentages of the TSCs of the rhizomes and their adventitious roots to those of all vegetative organs of the purple and green aerial stemmed plants, and the percentages of the TACs of the rhizomes and their adventitious roots to those of all vegetative organs of the purple aerial stemmed plants were increased. The increasing rates of the TACs of the aerial stems and all vegetative organs and the TSCs of the aerial stems, rhizomes and their adventitious roots and all vegetative organs of the purple aerial stemmed plants were always higher than those of the green aeria stemmed plants, but the increasing rates of the leaves TSCs were lower than those of the green aerial stemmed plants, and the content changes of the vegetative organ TACs and TSCs of the purple and green aerial stemmed plants exhibited different correlations. Additionally, the three-years-old plants, the TSCs of the vegetative organs of the purple aerial stemmed plants were all higher than those of the green aerial stemmed plants, but the TACs of the leaves and rhizomes and their adventitious roots were lower than those of the green aerial stemmed plants. Conclusion: The saponin-accumulating capacity of the vegetative organs of purple aerial stemmed Panax notoginseng plants is stronger than that of green aerial stemmed Panax notoginseng.

Increasing the sampling efficiency of protein conformational transition using velocity-scaling optimized hybrid explicit/implicit solvent REMD simulation.

The application of temperature replica exchange molecular dynamics (REMD) simulation on protein motion is limited by its huge requirement of computational resource, particularly when explicit solvent model is implemented. In the previous study, we developed a velocity-scaling optimized hybrid explicit/implicit solvent REMD method with the hope to reduce the temperature (replica) number on the premise of maintaining high sampling efficiency. In this study, we utilized this method to characterize and energetically identify the conformational transition pathway of a protein model, the N-terminal domain of calmodulin. In comparison to the standard explicit solvent REMD simulation, the hybrid REMD is much less computationally expensive but, meanwhile, gives accurate evaluation of the structural and thermodynamic properties of the conformational transition which are in well agreement with the standard REMD simulation. Therefore, the hybrid REMD could highly increase the computational efficiency and thus expand the application of REMD simulation to larger-size protein systems.

A homogeneous signal-on strategy for the detection of rpoB genes of Mycobacterium tuberculosis based on electrochemiluminescent graphene oxide and ferrocene quenching.

Tuberculosis (TB) remains one of the leading causes of morbidity and mortality all over the world and multidrug resistance TB (MDR-TB) pose a serious threat to the TB control and represent an increasing public health problem. In this work, we report a homogeneous signal-on electrochemiluminescence (ECL) DNA sensor for the sensitive and specific detection of rpoB genes of MDR-TB by using ruthenium(II) complex functionalized graphene oxide (Ru-GO) as suspension sensing interface and ferrocene-labeled ssDNA (Fc-ssDNA) as ECL intensity controller. The ECL of Ru-GO could be effectively quenched by Fc-ssDNA absorbed on the Ru-GO nanosheets. The Ru-GO has good discrimination ability over ssDNA and dsDNA. Mutant ssDNA target responsible for the drug resistant tuberculosis can hybridize with Fc-ssDNA and release Fc-ssDNA from Ru-GO surface, leading to the recovery of ECL. Mutant ssDNA target can be detected in a range from 0.1 to 100 nM with a detection limit of 0.04 nM. The proposed protocol is sensitive, specific, simple, time-saving and polymerase chain reaction free without complicated immobilization, separation and washing steps, which creates a simple but valuable tool for facilitating fast and accurate detection of disease related specific sequences or gene mutations.

Transcriptomics and metabolomics revealed the molecular basis of the color formation in the roots of Panax notoginseng.

Panax notoginseng is a traditional Chinese medicine rich in many pharmacological components. The root of the 'Miaoxiang Sanqi No. 2' is yellow or greenish yellow, while a novel cultivar-'Wenyuan Ziqi No. 1' shows purple root and is thought to have high medicinal value. Little information is available about the anthocyanin biosynthesis in P. notoginseng root. In this study, we compared the 'Miaoxiang Sanqi No. 2' and 'Wenyuan Ziqi No. 1' in morphological, transcriptional and metabolic levels. The results showed that purple rich in the periderm, rhizome and phloem around cambium of the 'Wenyuan Ziqi No. 1' root and cyanidin 3-O-galactoside was the main anthocyanin causing purple. Moreover, 'Wenyuan Ziqi No. 1' highly accumulated in 155 metabolites, including flavones, phenylpropanoids and lipids. Transcriptome data showed that phenylpropanoid biosynthesis pathway genes are highly expressed in 'Wenyuan Ziqi No. 1'. Conjoint analysis showed that anthocyanin biosynthesis pathway substances were highly accumulated in 'Wenyuan Ziqi No. 1', and the expression level of structural genes involved in anthocyanin biosynthesis pathway was higher in 'Wenyuan Ziqi No. 1'. Meanwhile, eight R2R3-MYB genes that might be involved in anthocyanin biosynthesis were identified. The comprehensive analysis of two cultivars provides new insights into the understanding of root coloration in P. notoginseng.

Photocobilins integrate B12 and bilin photochemistry for enzyme control.

Photoreceptor proteins utilise chromophores to sense light and trigger a biological response. The discovery that adenosylcobalamin (or coenzyme B12) can act as a light-sensing chromophore heralded a new field of B12-photobiology. Although microbial genome analysis indicates that photoactive B12-binding domains form part of more complex protein architectures, regulating a range of molecular-cellular functions in response to light, experimental evidence is lacking. Here we identify and characterise a sub-family of multi-centre photoreceptors, termed photocobilins, that use B12 and biliverdin (BV) to sense light across the visible spectrum. Crystal structures reveal close juxtaposition of the B12 and BV chromophores, an arrangement that facilitates optical coupling. Light-triggered conversion of the B12 affects quaternary structure, in turn leading to light-activation of associated enzyme domains. The apparent widespread nature of photocobilins implies involvement in light regulation of a wider array of biochemical processes, and thus expands the scope for B12 photobiology. Their characterisation provides inspiration for the design of broad-spectrum optogenetic tools and next generation bio-photocatalysts.

Label-free electrochemiluminescence immunosensor for cardiac troponin I using luminol functionalized gold nanoparticles as a sensing platform.

A simple and sensitive label-free electrochemiluminescence (ECL) immunosensor based on the use of luminol functionalized gold nanoparticles (luminol-AuNPs) as antibody carriers and sensing platform is described for detecting the acute myocardial infarction biomarker cTnI. The ECL immunosensor was fabricated by the assembly of luminol-AuNPs conjugated with biotinylated antibodies against cTnI (biotin-anti-cTnI-luminol-AuNPs) with the streptavidin coated AuNPs (SA-AuNPs) modified Au electrode directly by virtue of the biotin-SA system. The fabricated sensing platform exhibited stable and strong ECL intensity and could be used for the recognition of target antigen. In the presence of cTnI, a decrease in the ECL intensity was observed. Direct detection of the ECL signal changes during antigen-antibody immunoreactions can be used for the quantification of cTnI. The ECL response exhibited a quite wide dynamic range from 1000 ng mL(-1) down to 0.1 ng mL(-1). The proposed method has been successfully applied in the detection of cTnI in real plasma samples. This protocol is simple, fast, sensitive, specific, stable and reliable. This work reveals that the luminol-AuNPs are excellent sensing platforms for the fabrication of simple and sensitive immunosensors. Moreover, the proposed strategy may also be extended for the detection of other biomarkers, which is of great application potential in clinical and pharmaceutical analysis.

Structure-Based Design of Small Imine Reductase Panels for Target Substrates.

Biocatalysis is important in the discovery, development, and manufacture of pharmaceuticals. However, the identification of enzymes for target transformations of interest requires major screening efforts. Here, we report a structure-based computational workflow to prioritize protein sequences by a score based on predicted activities on substrates, thereby reducing a resource-intensive laboratory-based biocatalyst screening. We selected imine reductases (IREDs) as a class of biocatalysts to illustrate the application of the computational workflow termed IREDFisher. Validation by using published data showed that IREDFisher can retrieve the best enzymes and increase the hit rate by identifying the top 20 ranked sequences. The power of IREDFisher is confirmed by computationally screening 1400 sequences for chosen reductive amination reactions with different levels of complexity. Highly active IREDs were identified by only testing 20 samples in vitro. Our speed test shows that it only takes 90 min to rank 85 sequences from user input and 30 min for the established IREDFisher database containing 591 IRED sequences. IREDFisher is available as a user-friendly web interface (https://enzymeevolver.com/IREDFisher). IREDFisher enables the rapid discovery of IREDs for applications in synthesis and directed evolution studies, with minimal time and resource expenditure. Future use of the workflow with other enzyme families could be implemented following the modification of the workflow scoring function.

RetroBioCat Database: A Platform for Collaborative Curation and Automated Meta-Analysis of Biocatalysis Data.

Despite the increasing use of biocatalysis for organic synthesis, there are currently no databases that adequately capture synthetic biotransformations. The lack of a biocatalysis database prevents accelerating biocatalyst characterization efforts from being leveraged to quickly identify candidate enzymes for reactions or cascades, slowing their development. The RetroBioCat Database (available at retrobiocat.com) addresses this gap by capturing information on synthetic biotransformations and providing an analysis platform that allows biocatalysis data to be searched and explored through a range of highly interactive data visualization tools. This database makes it simple to explore available enzymes, their substrate scopes, and how characterized enzymes are related to each other and the wider sequence space. Data entry is facilitated through an openly accessible curation platform, featuring automated tools to accelerate the process. The RetroBioCat Database democratizes biocatalysis knowledge and has the potential to accelerate biocatalytic reaction development, making it a valuable resource for the community.

Mechanism of Action of Flavin-Dependent Halogenases.

To rationally engineer the substrate scope and selectivity of flavin-dependent halogenases (FDHs), it is essential to first understand the reaction mechanism and substrate interactions in the active site. FDHs have long been known to achieve regioselectivity through an electrophilic aromatic substitution at C7 of the natural substrate Trp, but the precise role of a key active-site Lys residue remains ambiguous. Formation of hypochlorous acid (HOCl) at the cofactor-binding site is achieved by the direct reaction of molecular oxygen and a single chloride ion with reduced FAD and flavin hydroxide, respectively. HOCl is then guided 10 Å into the halogenation active site. Lys79, located in this site, has been proposed to direct HOCl toward Trp C7 through hydrogen bonding or a direct reaction with HOCl to form an -NH2Cl+ intermediate. Here, we present the most likely mechanism for halogenation based on molecular dynamics (MD) simulations and active-site density functional theory "cluster" models of FDH PrnA in complex with its native substrate l-tryptophan, hypochlorous acid, and the FAD cofactor. MD simulations with different protonation states for key active-site residues suggest that Lys79 directs HOCl through hydrogen bonding, which is confirmed by calculations of the reaction profiles for both proposed mechanisms.

Dissemination and genome analysis of high-level ceftriaxone-resistant penA 60.001 Neisseria gonorrhoeae strains from the Guangdong Gonococcal antibiotics susceptibility Programme (GD-GASP), 2016-2019.

Background: After Neisseria gonorrhoeae FC428 was first found in Japan, ceftriaxone-resistant strains disseminated globally, and the gonococcal resistance rate increased remarkably. Epidemiological investigations are greatly significant for the analysis of antimicrobial resistance (AMR) trends, molecular features and evolution. Objectives: To clarify the AMR trend from 2016-2019 and reveal the molecular characteristics and evolution of ceftriaxone-resistant penA 60.001 isolates. Methods: The minimum inhibitory concentrations (MICs) of antibiotics against 4113 isolates were detected by the agar dilution method. N. gonorrhoeae multiantigen sequence typing (NG-MAST), multilocus sequence typing (MLST) and N.gonorrhoeae sequence typing for antimicrobial resistance (NG-STAR) were used to identify the sequence types. Genome analysis was conducted to analyze resistance genes, virulence factors, and evolutionary sources. Results: Isolates with decreased ceftriaxone susceptibility have increased from 2.05% (2016) to 16.18% (2019). Six ceftriaxone-resistant isolates possessing penA 60.001 appeared in Guangdong Province, and were resistant to ceftriaxone, penicillin, tetracycline, ciprofloxacin and cefixime, but susceptible to azithromycin and spectinomycin. Single-nucleotide polymorphisms (SNPs) in the porB gene were the major cause of different NG-MAST types. ST1903 was the main NG-STAR genotype and only strain-ZH545 was ST7365, with molecular features consistent with the MICs. Furthermore, different MLSTs suggested diverse evolutionary sources. Genome analysis revealed a set of virulence factors along with the resistance genes "penA" and "blaTEM-1B". Half of penA 60.001 strains were fully mixed with global FC428-related strains. Conclusions: Global FC428-related clones have disseminated across Guangdong, possibly causing decreased ceftriaxone susceptibility. Enhanced gonococcal surveillance will help elucidate the trajectory of transmission and curb further dissemination.

Emergence and Genomic Characterization of Neisseria gonorrhoeae Isolates with High Levels of Ceftriaxone and Azithromycin Resistance in Guangdong, China, from 2016 to 2019.

Currently, antibiotic resistance (especially ceftriaxone and azithromycin dual resistance) in Neisseria gonorrhoeae is the main obstacle affecting the efficacy of treatment. As analysis of drug sensitivity, molecular features, and dissemination of dual-resistant strains is important for gonococcal prevention and control, MIC, genotyping, and genome analysis were conducted to reveal the molecular characteristics and phylogeny of N. gonorrhoeae isolates. During 2016 to 2019, 5 out of 4,113 strains were defined as dual-resistant clones, with ceftriaxone MICs of 0.25 to ≥1 mg/L and azithromycin MICs of 2 to ≥2,048 mg/L. In particular, two strains with a ceftriaxone MIC above 0.5 mg/L were characterized as penA-60.001 FC428-related clones, and two isolates with a high-level azithromycin MIC above 1,024 mg/L featuring a 23S rRNA mutation were identified. Furthermore, phylogenetic analysis confirmed that the dual-resistant strains were closer to the evolutionary origin of F89 in France, global FC428-related clones, and high-level dual-resistant clones in Australia and the United Kingdom. Dual-resistant strains, including FC428-related clones and high-level azithromycin-resistant clones, have circulated in Guangdong, China. The ability of laboratories to perform real-time drug susceptibility and genetic analyses should be strengthened to monitor the spread of threatening strains. IMPORTANCE Here, we report five sporadic dual-resistant isolates, including FC428-related ceftriaxone-resistant clones with MICs of ≥0.5 mg/L and high-level azithromycin resistance with MICs of ≥1,024 mg/L. This study highlights that dual-resistant clones with the same evolutionary origin as FC428, A2735, and F89 have circulated in Guangdong, China, which suggests that the capacity for antibiotic resistance testing and genome analysis should be strengthened in daily epidemiological surveillance.