Polarity-Evolution Control and Luminescence Regulation in Multiple-Site Hydrogen-Bonded Organic Frameworks.

Hydrogen-bonded organic frameworks (HOFs) have shown great potential in separation, sensing and host-guest chemistry, however, the pre-design of HOFs remains challenging due to the uncertainty of solvents' participation in framework formation. Herein, the polarity-evolution-controlled framework/luminescence regulation is demonstrated based on multiple-site hydrogen-bonded organic frameworks. Several distinct HOFs were prepared by changing bonding modes of building units via the evolution of electrostatic forces induced by various solvent polarities. High-polar solvents with strong electrostatic attraction to surrounding units showed the tendency to form cage structures, while low-polar solvents with weak electrostatic attraction only occupy hydrogen-bond sites, conducive to the channel formation. Furthermore, the conformation of optical building unit can be adjusted by affecting the solvent polarity, generating different luminescence outputs. These results pave the way for the rational design of ideal HOFs with on-demand framework regulation and luminescence properties.

Molecular Characterization and Epidemiology of Carbapenem-Resistant Enterobacteriaceae Isolated from Pediatric Patients in Guangzhou, Southern China.

Background: Carbapenem-resistant Enterobacteriaceae (CRE) are spreading worldwide, posing a serious public health concern. However, the data on CRE strains that cause infections in children in Guangzhou remain limited. Therefore, this study aimed to investigate the epidemiology of CRE, drug resistance, and resistance mechanisms in children in Guangzhou, Southern China. Methods: In total, 54 nonrepetitive CRE strains were collected in pediatric patients at three centers in Guangzhou, Southern China, from January 2016 to August 2018. CRE isolates were used for further studies on antimicrobial susceptibility, the modified Hodge test (MHT), the modified carbapenem inactivation method (mCIM), and drug resistance genes. Multilocus sequence typing (MLST) was used to elucidate the molecular epidemiology of K. pneumoniae. Results: The isolated CRE strains include 34 K. pneumoniae (63.0%), 10 E. coli (18.5%), 4 Enterobacter cloacae (7.4%), and 6 Proteus mirabilis (11.1%) strains. The strains were isolated mainly from the blood (31.5%, n = 17), sputum (31.5%, n = 17), and urine (16.7%, n = 9). All CRE isolates were highly resistant to the third- or fourth-generation cephalosporins, carbapenems, and ß-lactam + ß-lactamase inhibitors (94.4%-96.3%). In addition, the resistance rates to amikacin, ciprofloxacin, levofloxacin, tigecycline, and colistin were 5.6%, 14.8%, 16.7%, 9.3%, and 0%, respectively. Carbapenemase was detected in 35 (64.8%) of the CRE isolates. The most dominant carbapenemase gene was bla NDM (n = 17, 48.6%), followed by bla IMP (n = 13, 37.1%) and bla OXA-23 (n = 4, 11.4%). Other carbapenemase genes (bla KPC, bla sim, bla Aim, bla GES, bla Gim, bla OXA-2 , and bla OXA-48 ) and the mcr-1 gene were not detected. MLST analysis showed high diversity among the K. pneumoniae, and ST45 (11.7%, 4/34) was the dominant sequence type. Conclusion: This study revealed bla NDM was the most dominant carbapenemase gene in children in Guangzhou. Infection control measures need to be taken for the prevention and treatment of CRE infections.

A Microporous Hydrogen Bonded Organic Framework for Highly Selective Separation of Carbon Dioxide over Acetylene.

The separation of acetylene (C2 H2 ) from carbon dioxide (CO2 ) is a very important but challenging task due to their similar molecular dimensions and physical properties. In terms of porous adsorbents for this separation, the CO2 -selective porous materials are superior to the C2 H2 -selective ones because of the cost- and energy-efficiency but have been rarely achieved. Herein we report our unexpected discovery of the first hydrogen bonded organic framework (HOF) constructed from a simple organic linker 2,4,6-tri(1H-pyrazol-4-yl)pyridine (PYTPZ) (termed as HOF-FJU-88) as the highly CO2 -selective porous material. HOF-FJU-88 is a two-dimensional HOFs with a pore pocket of about 7.6 Å. The activated HOF-FJU-88 takes up a high amount of CO2 (59.6 cm3 g-1 ) at ambient conditions with the record IAST selectivity of 1894. Its high performance for the CO2 /C2 H2 separation has been further confirmed through breakthrough experiments, in situ diffuse reflectance infrared spectroscopy and molecular simulations.

Hydration-Facilitated Coordination Tuning of Metal-Organic Frameworks toward Water-Responsive Fluorescence and Proton Conduction.

Developing smart stimuli-responsive metal-organic frameworks (MOFs) with diversified induced readable signals is highly desirable; however, reported multimode responsive MOFs are always achieved under strong environmental stimulations, making it difficult to keep MOF structures stable for practical applications. Herein, we reported a hydration-facilitated coordination tuning strategy to achieve the dual-mode water response in fluorescence and proton conduction from a single MOF. The designed MOF permitted reversible single-crystal transformation via the controllable hydration effect on metal nodes. The change in coordination modes leads to the regulation on conformations of optical ligands, contributing to the switch of fluorescence emissions. Moreover, the hydration effect adds additional hydrogen-bond sites in channels and optimizes hydrogen-bond networks, abruptly enhancing the proton conductivity by ∼20 times. These results pave new avenues for the exploitation of smart MOFs with multimode responsive behavior for on-demand sensing/detection applications.

Controlled Shape Evolution of Pure-MOF 1D Microcrystals towards Efficient Waveguide and Laser Applications.

MOF-based one-dimensional materials have received increasing attention in the nanophotonics field, but it is still difficult in the flexible shape evolution of MOF micro/nanocrystals for desired optical functionalities due to the susceptible solvothermal growth process. Herein, we report on the well-controlled shape evolution of pure-MOF microcrystals with optical waveguide and lasing performances based on a bottom-up and top-down synergistic method. The MOF microcrystals from solvothermal synthesis (bottom-up) enable the evolution from microrods via microtubes to nanowires through a chelating agent-assisted etching process (top-down). The three types of MOF 1D-microstructures with high crystallinity and smooth surfaces all exhibit efficient optical waveguide performance. Furthermore, MOF nanowire with lowest propagation loss served as low-threshold pure-MOF nanolasers with Fabry-Pérot resonance. These results advance the fundamental understanding on the controlled MOF evolution mechanism, and offer a valuable route for the development of pure-MOF-based photonic components with desired functionalities.

Pure Metal-Organic Framework Microlasers with Controlled Cavity Shapes.

Metal-organic frameworks (MOFs) are an emerging kind of laser material, yet they remain a challenge in the controlled fabrication of crystal nanostructures with desired morphology for tuning their optical microcavities. Herein, the shape-engineering of pure MOF microlasers was demonstrated based on the coordination-mode-tailored method. The one-dimensional (1D) microwires and 2D microplates were selectively fabricated through changing the HCl concentration to tailor the coordination modes. Both the single-crystalline microwires and microplates with strong optical confinement functioned as low-threshold MOF microlasers. Moreover, distinct lasing behaviors of 1D and 2D MOF microcrystals confirm a typical shape-dependent microcavity effect: 1D microwires serve as Fabry-Pérot (FP) resonators, and 2D microplates lead to the whispering-gallery-mode (WGM) microcavities. These results provide a special pathway for the exploitation of MOF-based micro/nanolasers with on-demand functions.

Steric-Hindrance-Controlled Laser Switch Based on Pure Metal-Organic Framework Microcrystals.

Herein, we demonstrated a steric-hindrance-controlled laser switch in pure metal-organic framework (MOF) microcrystals. The well-faceted MOF microwires with aggregation-induced emission (AIE) lumnogens as linkers function as typical Fabry-Pérot microlasers. The steric hindrance around the AIE linkers can be reduced by the loss of guest molecules, which lead to the enhanced rotation of linkers with red-shifted gain behavior. On this basis, the gain region was readily switched through changing the steric hindrance via the desorption/adsorption of guests. As a result, the reversible switching of the dual-wavelength lasing from MOF microwires was achieved. The results provide a promising route to the development of versatile micro-/nanolasers with desired applications.

Oral administration of recombinant Bacillus subtilis spores expressing Helicobacter pylori neutrophil-activating protein suppresses peanut allergy via up-regulation of Tregs.

BACKGROUND: Helicobacter pylori neutrophil-activating protein (NAP) is an immune modulator with anti-Th2 inflammation activity that can be used to prevent IgE-mediated allergic reactions. Cholera toxin B (CTB) is a mucosal adjuvant that can induce antigen tolerance. Bacillus subtilis spores are an ideal vehicle for the oral delivery of heterologous antigens. OBJECTIVE: We investigated the therapeutic effect of recombinant NAP B subtilis spores on peanut allergies in a mouse model. METHODS: Female C3H/HeJ mice were sensitized and challenged with peanut extract by oral administration. Before challenge, recombinant NAP and CTB-NAP (CNAP) spores were orally administered to sensitized mice for 4 weeks. Faecal peanut-specific IgA and serum-specific IgE, IgG1, and IgG2a levels were measured, and the intestinal microbiota was analysed. Mice were intraperitoneally injected with anti-CD25 antibodies for regulatory T cell (Treg) depletion to evaluate the efficacy of Tregs in preventing peanut allergy. After challenge, anaphylactic reactions, plasma histamine, Tregs, and splenocyte interleukin (IL)-10, IL-4, IL-5 and interferon-γ (IFN-γ) levels were evaluated. RESULTS: After 4 weeks of recombinant spore treatment, faecal IgA levels and serum IgG2a levels were increased, while serum IgG1 and IgE levels were reduced. Intestinal microbiota analysis revealed that CNAP spores increased the taxonomic abundance of Firmicutes at the phylum level and Clostridia at the class level. After challenge, the administration of NAP or CNAP spores to mice was found to ameliorate anaphylactic reactions and decrease plasma histamine levels. Administration of NAP or CNAP spores also enhanced IL-10 and IFN-γ secretion, and suppressed IL-4 and IL-5 secretion. The protective effect of CNAP spores was more pronounced than that of NAP spores; this therapeutic effect was lost after Treg depletion. CONCLUSIONS AND CLINICAL RELEVANCE: Recombinant NAP spores successfully suppressed Th2 inflammation via the up-regulation of Tregs; this may serve as a novel therapeutic approach for treating food allergies.

Smart-Responsive HOF Heterostructures with Multiple Spatial-Resolved Emission Modes toward Photonic Security Platform.

Luminescent hydrogen-bonded organic frameworks (HOFs) with the unique dynamics and versatile functional sites hold great potential application in information security, yet most of responsive HOFs focus on the single-component framework with restrained emission control, limiting further applications in advanced confidential information protection. Herein, the first smart-responsive HOF heterostructure with multiple spatial-resolved emission modes for covert photonic security platform is reported. The HOF heterostructures are prepared by integrating different HOFs into a single microwire based on a hydrogen-bond-assisted epitaxial growth method. The distinct responsive behaviors of HOFs permit the heterostructure to simultaneously display the thermochromism via the framework transformation and the acidichromism via the protonation effect, thus generating multiple emission modes. The dual stimuli-controlled spatial-resolved emission modes constitute the fingerprint of a heterostructure, and enable the establishment of the smart-responsive photonic barcode with multiple convert states, which further demonstrate the dynamic coding capability and enhanced security in anticounterfeiting label applications. These results offer a promising route to design function-oriented smart responsive HOF microdevices toward advanced anticounterfeiting applications.

Switchable Anisotropic/Isotropic Photon Transport in a Double-Dipole Metal-Organic Framework via Radical-Controlled Energy Transfer.

Directional control of photon transport at micro/nanoscale holds great potential in developing multifunctional optoelectronic devices. Here, the switchable anisotropic/isotropic photon transport is reported in a double-dipole metal-organic framework (MOF) based on radical-controlled energy transfer. Double-dipole MOF microcrystals with transition dipole moments perpendicular to each other have been achieved by the pillared-layer coordination strategy. The energy transfer between the double dipolar chromophores can be modulated by the photogenerated radicals, which permits the in situ switchable output on both polarization (isotropy/anisotropy state) and wavelength information (blue/red-color emission). On this basis, the original MOF microcrystal with isotropic polarization state displays the isotropic photon transport and similar reabsorption losses at various directions, while the radical-affected MOF microcrystal with anisotropic polarization state shows the anisotropic photon transport with distinct reabsorption losses at different directions, finally leading to the in situ switchable anisotropic/isotropic photon transport. These results offer a novel strategy for the development of MOF-based photonic devices with tunable anisotropic performance.

Prevalence, serotype, and antimicrobial resistance profiles of children infected with Salmonella in Guangzhou, southern China, 2016-2021.

Purpose: Salmonella infection is a key global public health concern and has lead to an increased economic burden on society. We investigated the epidemiological characteristics and antimicrobial resistance profiles of clinically isolated Salmonella strains in Guangzhou Women and Children's Medical Center. Patients and methods: This was a retrospective study of 1,338 Salmonella strains collected from children in Guangzhou Women and Children's Medical Center during 2016 to 2021. Results: The results revealed that 1,338 cases of Salmonella were mainly isolated from feces and blood samples. The age distribution was dominated by infants under 3 years old. The seasonal distribution was high in summer and autumn. 48 serotypes were detected, and S. typhimurium (78.7%) was the predominant serogroup. The results of antimicrobial susceptibility showed that the highest resistance was observed in ampicillin (84.5%), while lower resistance was observed in piperacillin/tazobactam, cefoperazone/sulbactam and ciprofloxacin. The antimicrobial resistance rate of fecal isolates was higher than that of blood isolates. The five-year average detection rate of multi-drug resistant Salmonella was 8.5% (114/1338) and the MDR rate of S. typhimurium was the lowest (6.9%; 73/1053). Conclusion: We concluded that antibacterial treatment should be carefully selected according to serotype and antimicrobial sensitivity results in children. Antimicrobial resistance monitoring for multi-drug resistant Salmonella is still required.

Fecal carriage and molecular epidemiology of mcr-1-harboring Escherichia coli from children in southern China.

BACKGROUND: The increase of multidrug-resistant Enterobacteriaceae bacteria has led to the reintroduction of colistin for clinical treatments, and colistin has become a last resort for infections caused by multidrug-resistant bacteria. Enterobacteriaceae bacteria carrying the mcr-1 gene are majorly related to colistin resistance, which may be the main reason for the continued increase in the colistin resistance rate of Enterobacteriaceae. The study aimed to investigate the sequence type and prevalence of Escherichia coli (E. coli) harboring the mcr-1 gene in the gut flora of children in southern China. METHODS: Fecal samples (n = 2632) of children from three medical centers in Guangzhou were cultured for E. coli. The mcr-1-harboring isolates were screened via polymerase chain reaction (PCR). The colistin resistance transfer frequency was studied by conjugation experiments. DNA sequencing data of seven housekeeping genes were used for multi-locus sequence typing analysis (MLST). RESULTS: PCR indicated that 21 of the 2632 E. coli (0.80%) isolates were positive for mcr-1; these strains were resistant to colistin. Conjugation experiments indicated that 18 mcr-1-harboring isolates could transfer colistin resistance phenotypes to E. coli J53. MLST analysis revealed that the 21 isolates were divided into 18 sequence types (STs); E. coli ST69 was the most common (14.3%), followed by E. coli ST58 (9.5%). CONCLUSION: These results demonstrate the colonization dynamics and molecular epidemiology of E. coli harboring mcr-1 in the gut flora of children in southern China. The mcr-1 gene can be horizontally transmitted within species; hence, it is necessary to monitor bacteria that harbor mcr-1 in children.

Clinical and molecular epidemiology of carbapenem-resistant Enterobacteriaceae in pediatric inpatients in South China.

IMPORTANCE: This study assessed the clinical and molecular epidemiology of carbapenem-resistant Enterobacteriaceae in pediatric inpatients at three hospitals in South China by means of screening stool samples for carbapenem-resistant genes and a nested case-control study to determine risk factors for carriage of carbapenem-resistant Enterobacteriaceae. Of 4,033 fecal samples screened, 158 (3.92%) were positive for CRE, including Escherichia coli (51.27 %), Klebsiella pneumoniae (37.97%), and Enterobacter cloacae (6.96%). The most common carbapenemase genes harbored by gastrointestinal CRE strains were blaNDM-5, blaNDM-1, and blaIMP-4. Hematological malignancies, respiratory diseases, otolaryngological diseases, nervous system diseases, oral administration of third-generation cephalosporins, and the combined use of two or more antibiotics were independently associated with CRE colonization.

Coordination-Guided Conformational Locking of 1D Metal-Organic Frameworks for a Tunable Stimuli-Responsive Luminescence Region.

One-dimensional (1D) metal-organic frameworks (MOFs) have shown great potential for designing more sensitive and smart stimuli-responsive photoluminescence metal-organic frameworks (PL-MOFs). Herein, we propose a strategy for constructing the 1D MOFs with tunable stimuli-responsive luminescence regions based on coordination-guided conformational locking. Two flexible 1D MOF microcrystals with trans- and cis-coordination modes, respectively, were synthesized by controlling the spatial constraint of solvents. The two 1D frameworks possess different conformation lockings of gain ligands, which have a great influence on the rotating restrictions and corresponding excited-state behaviors, generating the remarkably distinct color-tunable ranges (cyan-blue to green and cyan-blue to yellow, respectively). On this basis, the two 1D MOF materials, benefiting from the varied stimuli-responsive ranges, have displayed great potential in fulfilling the anticounterfeiting and information encryption applications. These results provide valuable guidance for the development of smart MOF-based stimuli-responsive materials in information identification and data encryption.

Inhibition of Galectin-3 Impairs Antifungal Immune Response in Fungal Keratitis.

Galectin-3 is one of the galectin family members which are master regulators of immune homeostasis, especially in infectious diseases. However, its mechanism of immune regulation in fungal keratitis has not been thoroughly studied. Our study is aimed at clarifying the role of galectin-3 in the fungal keratitis mouse model in vivo, thereby providing a new biomarker of antifungal therapy. In our study, aspergillus, the most common pathogenic fungi of fungal keratitis, was identified and isolated by corneal tissue fungus culture. Then, the RNA expression levels of galectin family members in corneas of the mouse model with aspergillus fumigatus keratitis were screened by transcriptome sequencing (RNA-seq). The expression of the galectin-3 was detected by quantitative real-time Polymerase Chain Reaction (qPCR), enzyme-linked immunosorbent assay (ELISA), and immunofluorescence in the corneal tissue of the fungal keratitis mouse model. Recruitment of neutrophils and the co-immunofluorescence of galectin-3 and related markers in corneal tissue were determined by flow cytometry analysis and immunofluorescence staining. The regulatory role of galectin-3 for proinflammatory cytokines and neutrophils was validated by the knockout mouse model. Galectin-3 knockout deteriorated the condition for the inhibition of galectin-3 was benefecial for fungi to survive and thrive in corneal lesions. These results demonstrated that in the ocular fungal infection, galectin-3 is capable of regulating the pathogenesis of fungal keratitis by modulating neutrophil recruitment. The deterioration of fungal keratitis and increased fungal load in corneal lesions of galectin-3 knockout mice proved the regulatory role of galectin-3 in fungal keratitis. In conclusion, galectin-3 is going to be an essential target to modulate neutrophil recruitment and its related antifungal immune response in fungal keratitis.

Framework-Shrinkage-Induced Wavelength-Switchable Lasing from a Single Hydrogen-Bonded Organic Framework Microcrystal.

Porous organic materials (POMs) have shown great potential for fabricating tunable miniaturized lasers. However, most pure-POM micro/nanolasers are achieved via coordination interactions, during which strong charge exchanges inevitably destroy the intrinsic gain property and even lead to optical quenching, hindering their practical applications. Herein, we reported on an approach to realize hydrogen-bonded organic framework (HOF)-based in situ wavelength-switchable lasing based on the framework-shrinkage effect. A flexible HOF with reversible framework shrinkage was constructed from gain blocks with multiple rotors. The framework shrinkage of the HOF induced the in situ regulation on the conformation and conjugation degree of gain blocks, leading to distinct energy-level structures with blue/green-color gain emissions. Inspired by this, the in situ wavelength-switchable lasing from HOF microcrystals was achieved through reversibly controlling the framework shrinkage via the absorption/desorption of guests. The results offer useful insight into the use of flexible HOFs for exploiting miniaturized lasers with on-demand nanophotonics performance.

Genomic Basis of Occurrence of Cryptic Resistance among Oxacillin- and Cefoxitin-Susceptible mecA-Positive Staphylococcus aureus.

The oxacillin- and cefoxitin-susceptible mecA-positive Staphylococcus aureus is a novel "stealth" methicillin-resistant S. aureus (MRSA) type. Here, we sequenced the whole genome of two oxacillin- and cefoxitin-susceptible mecA-positive MRSA isolates from breast abscesses in a lactating woman and a nasal swab of a healthy student in Guangzhou for investigating the mechanism underlying its occurrence. The reversion of these isolates was selected by exposure to sub-MICs of cefoxitin with or without mupirocin. The mecA expression of both parental strains and their revertants was determined, and the whole genome of the revertants was sequenced. Comparative whole-genome analyses performed for both strains revealed that mecA of the clinical strain was mutated by a single-bp insertion at the 262nd position in the tandem repeat region of the gene, and this mutation that led to the formation of a premature stop codon. The colonizing strain was mutated by a novel G-to-A base substitution in the second promoter region (-35 bp) of mecA. The mecA expression level of strain 697 revertant was 37 times higher than that of the parental strain. Although the mecA expression level was even higher for parental strain 199 compared with that for its revertant, its cDNA sequence contained a single-bp insertion. Collectively, both the missense and single substitution mutations of the second promoter of mecA could render MRSA isolates as "stealth" MRSA, thereby emphasizing the importance of combining phenotype tests with mecA or penicillin-binding protein 2a detection for the identification of MRSA. IMPORTANCE The oxacillin- and cefoxitin-susceptible mecA-positive Staphylococcus aureus is a novel type of "stealth" methicillin-resistant S. aureus (MRSA), which is difficult to be detected using conventional methods. To investigate the genomic basis of their occurrence, we sequenced the whole genome of two previously recovered oxacillin- and cefoxitin-susceptible mecA-positive MRSA isolates from breast abscesses in a lactating woman and a nasal swab of a healthy student in Guangzhou. Complete SCCmec structure was absent except for mecA in clinical isolate 199. Additionally, a novel single-base pair insertion was observed in the clinical strain, which resulted in premature termination and a frameshift mutation. The colonizing isolate 697 had a Scc-mec-type IVa, and the second promoter region (-35 bp) of mecA was mutated by a novel G-to-A base substitution. The reversion of oxacillin- and cefoxitin-susceptible mecA-positive S. aureus to resistant MRSA isolates was selected by exposure to subminimum inhibitory cefoxitin with or without mupirocin.

Distribution of Biocide Resistance Genes and Association with Clonal Complex Genotypes in Staphylococcus aureus Isolated from School-Age Children in Guangzhou.

Purpose: Chlorhexidine and mupirocin are often prescribed to children in affected communities to prevent colonization and transmission of Staphylococcus aureus, but this has led to an increasing rate of biocide resistance. In this study, we aimed to determine the distribution of biocide resistance genes among S. aureus isolates from school-age children in Guangzhou, investigate chlorhexidine gluconate and mupirocin susceptibility and clonal complex (CC) genotypes in strains carrying biocide-resistance genes, and further explore the role of biofilms in this resistance. Patients and Methods: Antibiotic resistance and multilocus sequence genotyping were performed on 722 S. aureus isolates from previous study. The distribution of nine biocide genes (qacA/B, mupA, mepA, sepA, norA, lmrS, smr, mupB, qacG) was determined by PCR. Isolates carrying qacA/B or mupA genes were further tested for susceptibility to chlorhexidine gluconate (CHG) and mupirocin and biofilm formation abilities. Results: The most prevalent of the nine biocide resistance genes were mepA (95.57%), followed by norA (78.81%), lmrS (77.01%), and sepA (58.17%). The qacG gene was not detected. Distribution of sepA was significantly decreased in CC30 and CC45 genotypes, and presence of sepA was associated with resistance to antibiotics such as CLI, ERY, TCY, SXT, CIP, and LVX. In addition, 64 (94.1%, n=68) qacA/B+ isolates showed CHG resistance, 12 (100.0%, n=12) mupA+ isolates were mupirocin resistant, and 4 (80%, n=5) and 5 (100%, n=5) qacA/B+mupA+ isolates were CHG and mupirocin resistant, respectively. Of these 85 isolates, 98.8% (n=84) had different degrees of biofilm-forming abilities, which were positively associated with CHG and mupirocin resistance. Conclusion: The distribution of biocide resistance genes was associated with special CCs. The qacA/B and mupA genes are highly associated with resistance to CHG and mupirocin, and biofilm formation was found to contribute to this biocide resistance.

Hydrogen-Bonded Organic Framework Microlasers with Conformation-Induced Color-Tunable Output.

Porous organic frameworks have emerged as the promising platforms to construct tunable microlasers. Most of these microlasers are achieved from metal-organic frameworks via meticulously accommodating the laser dyes with the sacrifice of the pore space, yet they often suffer from the obstacles of either relatively limited gain concentration or sophisticated fabrication techniques. Herein, we reported on the first hydrogen-bonded organic framework (HOF) microlasers with color-tunable performance based on conformation-dependent stimulated emissions. Two types of HOF microcrystals with the same gain lumnogen as the building block were synthesized via a temperature-controlled self-assembly method. The distinct frameworks offer different conformations of the gain building block, which lead to great impacts on their conjugation degrees and excited-state processes, resulting in remarkably distinct emission colors (blue and green). Accordingly, blue/green-color lasing actions were achieved in these two types of HOFs based on well-faceted assembled wire-like cavities. These results offer a deep insight on the exploitation of HOF-based miniaturized lasers with desired nanophotonics performances.

Active Surveillance, Drug Resistance, and Genotypic Profiling of Staphylococcus aureus Among School-Age Children in China.

Methicillin-susceptible (MSSA) and methicillin-resistant Staphylococcus aureus (MRSA) nasal colonization predisposes individuals for endogenous infections and is a major threat to children. Recently, oxacillin/cefoxitin-susceptible mecA-positive S. aureus (OS-MRSA) has been reported worldwide. Herein, a prospective, cross-sectional study was conducted across five schools, representing three educational stages, in Guangzhou, China. Nasal swabs from 2,375 students were cultured for S. aureus and all isolates were subjected to antibiotic susceptibility testing phenotypically and confirmed by femB and mecA genetic detection; all the isolates were classified as MSSA, MRSA, or OS-MRSA. All strains were also analyzed by multi-locus sequence typing. Among the 2,375 swabs, S. aureus was detected in 744 children (31.3%, 95% CI: 25.9-36.7%), of whom 72 had MRSA (3.0%, 95% CI: 0.6-5.4%) and 4 had OS-MRSA (0.2%, 95% CI: 0.1-0.3%), of which an oxacillin- and cefoxitin-susceptible MRSA strain was identified. The prevalence of S. aureus and MRSA was higher in younger children. The highest percentage of drug resistance of the S. aureus isolates (n = 744) was to penicillin (85.5%), followed by erythromycin (43.3%) and clidamycin (41.0%). The most prevalent sequence types (STs) were ST30, ST45, and ST188 in MSSA, accounting for 38.7% of the total isolates, whereas ST45, ST59, and ST338 accounted for 74.6% of the MRSA isolates and ST338 accounted for 50.0% of the OS-MRSA isolates. The MRSA and OS-MRSA isolates (n = 76) were grouped into three clades and one singleton, with clonal complex (CC) 45 as the most predominant linkage. The top nine multi-locus sequence typing-based CCs (CC30, CC45, CC5, CC1, CC15, CC944, CC398, CC59, CC7) represented 86.7% of all S. aureus isolates. All CC30 isolates were resistant to erythromycin and clidamycin, and almost all these isolates were also resistant to penicillin (99.2%). The CC45 and CC59 isolates exhibited high resistance rates to oxacillin at 31.5 and 59.0%, respectively. This study provides updated data valuable for designing effective control strategies to mitigate the burden of disease and to improve the adequacy of empirical antimicrobial treatments for potentially harmful infections.