Identification and characteristics of a novel aminoglycoside phosphotransferase, APH(3')-IId, from an MDR clinical isolate of Brucella intermedia.

OBJECTIVES: To describe a novel chromosomal aminoglycoside phosphotransferase named APH(3')-IId identified in an MDR Brucella intermedia ZJ499 isolate from a cancer patient. METHODS: Species identity was determined by PCR and MALDI-TOF MS analysis. WGS was performed to determine the genetic elements conferring antimicrobial resistance. Gene cloning, transcriptional analysis and targeted gene deletion, as well as protein purification and kinetic analysis, were performed to investigate the mechanism of resistance. RESULTS: APH(3')-IId consists of 266 amino acids and shares the highest identity (48.25%) with the previously known APH(3')-IIb. Expression of aph(3')-IId in Escherichia coli decreased susceptibility to kanamycin, neomycin, paromomycin and ribostamycin. The aph(3')-IId gene in ZJ499 was transcriptionally active under laboratory conditions and the relative abundance of this transcript was unaffected by treatment with the above four antibiotics. However, deletion of aph(3')-IId in ZJ499 results in decreased MICs of these drugs. The purified APH(3')-IId showed phosphotransferase activity against kanamycin, neomycin, paromomycin and ribostamycin, with catalytic efficiencies (kcat/Km) ranging from ∼105 to 107 M-1 s-1. Genetic environment and comparative genomic analyses suggested that aph(3')-IId is probably a ubiquitous gene in Brucella, with no mobile genetic elements detected in its surrounding region. CONCLUSIONS: APH(3')-IId is a novel chromosomal aminoglycoside phosphotransferase and plays an important role in the resistance of B. intermedia ZJ499 to kanamycin, neomycin, paromomycin and ribostamycin. To the best of our knowledge, APH(3')-IId represents the fourth characterized example of an APH(3')-II enzyme.

Prevalence and outcomes of re-positive nucleic acid tests in discharged COVID-19 patients.

The prevalence and outcomes of patients who had re-activation of coronavirus disease 2019 (COVID-19) after discharge remain poorly understood. We included 126 consecutively confirmed cases of COVID-19 with 2-month follow-up data after discharge in this retrospective study. The upper respiratory specimen using a reverse-transcription polymerase chain reaction test of three patients (71 years [60-76]) were positive within 11-20 days after their discharge, with an event rate of 19.8 (95%CI 2.60-42.1) per 1,000,000 patient-days. Moreover, all re-positive patients were asymptomatic. Our findings suggest that few recovered patients may still be virus carriers even after reaching the discharge criteria.

Six-month follow-up of functional status in discharged patients with coronavirus disease 2019.

BACKGROUND: The long-term functional outcome of discharged patients with coronavirus disease 2019 (COVID-19) remains unresolved. We aimed to describe a 6-month follow-up of functional status of COVID-19 survivors. METHODS: We reviewed the data of COVID-19 patients who had been consecutively admitted to the Tumor Center of Union Hospital (Wuhan, China) between 15 February and 14 March 2020. We quantified a 6-month functional outcome reflecting symptoms and disability in COVID-19 survivors using a post-COVID-19 functional status scale ranging from 0 to 4 (PCFS). We examined the risk factors for the incomplete functional status defined as a PCFS > 0 at a 6-month follow-up after discharge. RESULTS: We included a total of 95 COVID-19 survivors with a median age of 62 (IQR 53-69) who had a complete functional status (PCFS grade 0) at baseline in this retrospective observational study. At 6-month follow-up, 67 (70.5%) patients had a complete functional outcome (grade 0), 9 (9.5%) had a negligible limited function (grade 1), 12 (12.6%) had a mild limited function (grade 2), 7 (7.4%) had moderate limited function (grade 3). Univariable logistic regression analysis showed a significant association between the onset symptoms of muscle or joint pain and an increased risk of incomplete function (unadjusted OR 4.06, 95% CI 1.33-12.37). This association remained after adjustment for age and admission delay (adjusted OR 3.39, 95% CI 1.06-10.81, p = 0.039). CONCLUSIONS: A small proportion of discharged COVID-19 patients may have an incomplete functional outcome at a 6-month follow-up; intervention strategies are required.

Prevalence of Aminoglycoside Resistance Genes and Molecular Characterization of a Novel Gene, aac(3)-IIg, among Clinical Isolates of the Enterobacter cloacae Complex from a Chinese Teaching Hospital.

Members of the Enterobacter cloacae complex are important opportunistic human pathogens capable of causing a wide variety of infections. During recent decades, aminoglycoside-resistant E. cloacae complex isolates have increasingly been reported and have become a major concern. Here, we employed high-throughput sequencing in combination with specific PCR assays to investigate the prevalence of aminoglycoside resistance genes among 170 isolates of the E. cloacae complex collected from a teaching hospital in Wenzhou, China. A total of 12 known genes [aphA-1, strA, strB, aac(6')-IIc, aadA2, aac(3)-IId, aadB, aadA1, rmtB, armA, aadA5, and aac(6')-Ie-aph(2'')-Ia] and 1 novel gene [aac(3)-IIg] were identified, with aphA-1 (71.18%), strA (55.29%), and strB (52.35%) being the most prevalent, and aac(3)-IIg was detected with a positive rate of 21.76% (37/170). The aac(3)-IIg gene was 810 bp in length and encoded a protein that shared 72 to 78% identities with previously known AAC(3)-II aminoglycoside 3-N-acetyltransferases. The MICs of gentamicin and tobramycin were 512 µg/ml and 64 µg/ml, respectively, when aac(3)-IIg was cloned into Escherichia coli DH5α. All aac(3)-IIg-positive isolates exerted broad aminoglycoside resistance profiles, mediated by the coexistence of multiple resistance genes. Moreover, aminoglycoside resistance and resistance genes were found to be transferable in most strains (24/37). Nevertheless, pulsed-field gel electrophoresis (PFGE) and dendrogram analysis showed clonal diversity among these isolates. S1 nuclease PFGE, Southern hybridization, and whole-genome sequencing indicated that aac(3)-IIg was located on transferable as well as nontransferable plasmids of various sizes. The analysis of the genetic environment suggested that aac(3)-IIg is embedded within a class 1 integron, with IS26 playing an important role in its mobility.

The effect of vascular risk factor burden on the severity of COVID-19 illness, a retrospective cohort study.

BACKGROUND: Patients with cardiovascular comorbidities are at high risk of poor outcome from COVID-19. However, how the burden (number) of vascular risk factors influences the risk of severe COVID-19 disease remains unresolved. Our aim was to investigate the association of severe COVID-19 illness with vascular risk factor burden. METHODS: We included 164 (61.8 ± 13.6 years) patients with COVID-19 in this retrospective study. We compared the difference in clinical characteristics, laboratory findings and chest computed tomography (CT) findings between patients with severe and non-severe COVID-19 illness. We evaluated the association between the number of vascular risk factors and the development of severe COVID-19 disease, using a Cox regression model. RESULTS: Sixteen (9.8%) patients had no vascular risk factors; 38 (23.2%) had 1; 58 (35.4%) had 2; 34 (20.7%) had 3; and 18 (10.9%) had ≥4 risk factors. Twenty-nine patients (17.7%) experienced severe COVID-19 disease with a median (14 [7-27] days) duration between onset to developing severe COVID-19 disease, an event rate of 4.47 per 1000-patient days (95%CI 3.10-6.43). Kaplan-Meier curves showed a gradual increase in the risk of severe COVID-19 illness (log-rank P < 0.001) stratified by the number of vascular risk factors. After adjustment for age, sex, and comorbidities as potential confounders, vascular risk factor burden remained associated with an increasing risk of severe COVID-19 illness. CONCLUSIONS: Patients with increasing vascular risk factor burden have an increasing risk of severe COVID-19 disease, and this population might benefit from specific COVID-19 prevention (e.g., self-isolation) and early hospital treatment measures.

Problem Management Plus in the treatment of mental disorders in patients with multiple myeloma.

OBJECTIVES: In this study, Problem Management Plus (PM+) was used for patients with multiple myeloma (MM), to develop a care model of psychology and quality of life. METHODS: Forty cases received psychological management (PM+ group), and 40 cases underwent investigation without management (non-PM+ group). Patients were assessed using PSYCHLOPS, WHO DAS 2.0, and HADS (see Supplementary File 1). RESULTS: The results showed that the PM+ group showed reductions in Psychological Outcome Profile scores (6.3 ± 2.9) following program completion (preprogram scores: 16.0 ± 1.9, P < .05). The non-PM+ group showed differences between preprogram (16.7 ± 1.8) and postprogram scores (14.8 ± 2.6, P < .05). The effect size of the PM+ group exceeded that of the non-PM+ group (5.1 to 1.0). In the Hospital Anxiety and Depression Scale, the PM+ group showed reductions in anxiety (6.4 ± 1.8) and depression (5.4 ± 0.7) (preprogram scores: 14.7 ± 4.3, P < .05 and 10.9 ± 2.6, P < .05, respectively). In the Hospital Anxiety and Depression Scale, scores for mobility, self-care, getting along, life activities, and participation decreased in the PM+ group following program completion (all P's < .05) but did not decrease in the non-PM+ group (all P > .05). CONCLUSION: The PM+ strategy could help patients to alleviate symptoms of anxiety and depression and strengthen social support, to aid in the management of problems and improve mental disorders. IMPACT STATEMENT: MM patients often experienced mental disorders and wished to participate in psychosocial interventions; the PM+ strategies should be as a wide to help patients manage their problems and alleviate the symptoms of anxiety and depression.

Altered dynamic functional connectivity in the default mode network in patients with cirrhosis and minimal hepatic encephalopathy.

PURPOSE: Abnormal brain intrinsic functional connectivity (FC) has been documented in minimal hepatic encephalopathy (MHE) by static connectivity analysis. However, changes in dynamic FC (dFC) remain unknown. We aimed to identify altered dFC within the default mode network (DMN) associated with MHE. METHODS: Resting-state functional MRI data were acquired from 20 cirrhotic patients with MHE and 24 healthy controls. DMN seed regions were defined using seed-based FC analysis (centered on the posterior cingulate cortex (PCC)). Dynamic FC architecture was calculated using a sliding time-window method. K-means clustering (number of clusters = 2-4) was applied to estimate FC states. RESULTS: When the number of clusters was 2, MHE patients presented weaker connectivity strengths compared with controls in states 1 and 2. In state 1, decreased FC strength was found between the PCC/precuneus (PCUN) and right medial temporal lobe (MTL)/bilateral lateral temporal cortex (LTC); left inferior parietal lobule (IPL) and right MTL/left LTC; right IPL and right MTL/bilateral LTC; right MTL and right LTC; and medial prefrontal cortex (MPFC) and right MTL/bilateral LTC. In state 2, reduced FC strength was observed between the PCC/PCUN and bilateral MTL/bilateral LTC; left IPL and left MTL/bilateral LTC/MPFC; and left LTC and right LTC. Altered connectivities from state 1 were correlated with patient cognitive performance. Similar findings were observed when the number of clusters was set to 3 or 4. CONCLUSION: Aberrant dynamic DMN connectivity is an additional characteristic of MHE. Dynamic connectivity analysis offers a novel paradigm for understanding MHE-related mechanisms.

A surface molecularly imprinted polymer as chiral stationary phase for chiral separation of 1,1'-binaphthalene-2-naphthol racemates.

Acrylamide (AM) was copolymerized with ethylene glycol dimethacrylate (EGDMA) in the presence of (R)-1,1'-binaphthalene-2-naphthol (BINOL) as the template molecules on the surface of silica gel by a free radical polymerization to produce a chiral stationary phase based on the surface molecularly imprinted polymer (SMIP-CSP). The SMIP-CSP showed a much better separation factor (α = 4.28) than the CSP based on the molecularly imprinted polymer (MIP-CSP) without coating on the silica gel (α = 1.96) during the chiral separation of BINOL enantiomers by high-performance liquid chromatography. The influence of the pretreatment temperature and the content of the template molecule ((R)-BINOL) of the SMIP-CSP, and the mobile phase composition on the separation of the racemic BINOL were systematically investigated.

Efficacy and safety of interferon-α2b spray in the treatment of hand, foot, and mouth disease: a multicenter, randomized, double-blind trial.

Hand, foot, and mouth disease (HFMD) is a common infectious enterovirus disease, occurring mostly in infants and children younger than 7 years with potentially fatal complications. Therefore, we evaluated the clinical efficacy and safety of recombinant human interferon (IFN)-α2b spray for treating mild HFMD in 400 patients in a randomized, open, controlled clinical trial. The patients were randomized to the IFN-α2b spray and placebo groups, and their temperature, skin rash, oral lesions, and appetite were monitored, while pathogen levels and safety were evaluated with a 7-day follow-up. The mean age of the patients was 20.1 ± 10.2 months. The median duration of fever, oral ulcers or vesicles (or both), and skin rash in addition to median time to regain appetite in the IFN-α2b spray group were shorter than they were in the placebo group. The number of virus-positive cases differed statistically between the two groups for the three follow-up detections. Additionally, the incidences of adverse events (AEs) and severe AEs (SAEs) were not significantly different between the two groups, and the SAEs were evidently unrelated to the IFN-α2b spray or placebo. Therefore, the IFN-α2b spray is suitable for topical treatment of HFMD, and it rapidly relieved fever, promoted oral lesions and subsidence of rash, enhanced appetite, promoted disease recovery, and was safe for application.

Evaluation of a nurse-led management program to complement the treatment of adolescent acute lymphoblastic leukemia patients.

PURPOSE: To evaluate a nurse-led management model of adolescent acute lymphoblastic leukemia (ALL) patients and improve their psychological care and quality of life. METHODS: Seventy-three adolescent ALL patients participated in an open, controlled clinical trial and were randomized into a nurse-led management model group (n=36) and a doctor-led management model group (n=37). Two assessment questionnaires were administered to assess and compare the 2 models during a 1.5-year follow-up period: the hospital anxiety and depression scale (HADS) questionnaire was administered at 6 different time points, and the European Organization for Research and Treatment of Cancer (EORTC) Quality of Life Questionnaire Core 30 (QLQ-C30) at 3 different time points. RESULTS: There were no differences in anxiety and depression between the groups according to the first-administered questionnaire (the mean anxiety and depression scores of the nurse-led group were 14.2±4.1 and 10.8±2.7, respectively; those of the doctor-led group were 13.8±3.8 and 10.6±2.2, respectively). However, repeated measures analysis of variance detected differences in subsequent HADS-based scores as a function of time between the 2 groups (p<0.05). Moreover, the Holm-Sidak's multiple comparisons tests showed that patients of the nurse-led group had significantly decreased mean anxiety scores compared to those in the doctor-led group at the third and subsequent sessions, as well as in mean depression scores from the second session onwards (all p<0.05). According to the last-administered EORTC QLQ-C30 questionnaire, there were statistical differences in cognitive, emotional, social, and quality of life scales between the 2 groups (all p<0.05), but not in role and physical scales (all p>0.05). CONCLUSIONS: It is necessary to offer unique cognitive, psychological, and behavioral management models to adolescent ALL patients that are tailored toward their age group. Strengthening such management is more conducive to alleviating or even reversing psychological problems, and to improving patients' quality of life while ensuring complication-free follow-up periods.

Coordination-induced and tunable layered rare-earth hydroxide-complex intercalated nanohybrid phosphorescent photosensitizer and therapy.

Hydrotalcite intercalated nanohybrid has served as a vital phosphorescent photosensitizer owing to remarkable 1O2 quantum yield and high cell mortality performance. However, it is rather difficult for potential large or complex guest phosphors to directly intercalate into the hydrotalcite gallery. Hence, it is necessary to regulate the interlayer microenvironment of hydrotalcites firstly for outstanding photosensitive properties. Herein, two isomers, 5,5'BDA and 4,4'BDA, with distinctive dual coordinative features were selected to modify the layer microenvironment of the LGdH gallery and induce the introduction of prospective Gd(HPhN)3 phosphorescent complexes into hydrotalcite through two different coordination effects successively. A LGdH-BDA-Gd(HPhN)3 intercalated nanohybrid phosphorescent photosensitizer was successfully obtained. The results indicated that the more efficient improvement was observed from 5,5'BDA due to offering a more spacious and stable space. Specifically, LGdH-5,5'BDA-Gd(HPhN)3 showed significantly better room temperature phosphorescence properties than LGdH-4,4'BDA-Gd(HPhN)3, whose lifetime was nearly 15 times longer than the latter. Additionally, the LGdH-5,5'BDA-Gd(HPhN)3 system displayed superior singlet oxygen generation in vitro under 460 nm irradiation (the quantum yield Φ = 0.48) and outstanding photodynamic therapy performance in tumor cells. LGdH presented more remarkable enhancement performance on the RTP properties of the luminescent molecules. This work provides a novel platform for designing a high-performance hydrotalcite intercalated nanohybrid phosphorescent photosensitizer through coordination induction to regulate the layer microenvironment.

Renewable biomass reinvigorates sustainable water-energy nexus.

The water-energy nexus has garnered worldwide interest. Current dual-functional research aimed at co-producing freshwater and electricity faces significant challenges, including sub-optimal capacities ("1 + 1 < 2"), poor inter-functional coordination, high carbon footprints, and large costs. Mainstream water-to-electricity conversions are often compromised owing to functionality separation and erratic gradients. Herein, we present a sustainable strategy based on renewable biomass that addresses these issues by jointly achieving competitive solar-evaporative desalination and robust clean electricity generation. Using hydrothermally activated basswood, our solar desalination exceeded the 100% efficiency bottleneck even under reduced solar illumination. Through simple size-tuning, we achieved a high evaporation rate of 3.56 kg h-1 m-2 and an efficiency of 149.1%, representing 128%-251% of recent values without sophisticated surface engineering. By incorporating an electron-ion nexus with interfacial Faradaic electron circulation and co-ion-predominated micro-tunnel hydrodynamic flow, we leveraged free energy from evaporation to generate long-term electricity (0.38 W m-3 for over 14d), approximately 322% of peer performance levels. This inter-functional nexus strengthened dual functionalities and validated general engineering practices. Our presented strategy holds significant promise for global human-society-environment sustainability.

Whole-tumor histogram models based on quantitative maps from synthetic MRI for predicting axillary lymph node status in invasive ductal breast cancer.

PURPOSE: To investigate the potential of using histogram analysis of synthetic MRI (SyMRI) images before and after contrast enhancement to predict axillary lymph node (ALN) status in patients with invasive ductal carcinoma (IDC). METHODS: From January 2022 to October 2022, a total of 212 patients with IDC underwent breast MRI examination including SyMRI. Standard T2 weight images, DCE-MRI and quantitative maps of SyMRI were obtained. 13 features of the entire tumor were extracted from these quantitative maps, standard T2 weight images and DCE-MRI. Statistical analyses, including Student's t-test, Mann-Whiney U test, logistic regression, and receiver operating characteristic (ROC) curves, were used to evaluate the data. The mean values of SyMRI quantitative parameters derived from the conventional 2D region of interest (ROI) were also evaluated. RESULTS: The combined model based on T1-Gd quantitative map (energy, minimum, and variance) and clinical features (age and multifocality) achieved the best diagnostic performance in the prediction of ALN between N0 (with non-metastatic ALN) and N+ group (metastatic ALN ≥ 1) with the AUC of 0.879. Among individual quantitative maps and standard sequence-derived models, the synthetic T1-Gd model showed the best performance for the prediction of ALN between N0 and N+ groups (AUC = 0.823). Synthetic T2_entropy and PD-Gd_energy were useful for distinguishing N1 group (metastatic ALN ≥ 1 and ≤ 3) from the N2-3 group (metastatic ALN > 3) with an AUC of 0.722. CONCLUSIONS: Whole-tumor histogram features derived from quantitative parameters of SyMRI can serve as a complementary noninvasive method for preoperatively predicting ALN metastases.

Repeated small-volume exchange transfusion for hyperleukocytosis in pediatric acute leukemia: A retrospective analysis.

Introduction: Leukapheresis reduces hyperleukocytosis in children with acute leukemia. Although the usefulness of this procedure is under debate, a repeated small-volume exchange transfusion along with leukapheresis yielded satisfactory results. Methods: Forty-seven patients with acute leukemia [32 acute lymphocytic leukemia (ALL) and 15 acute myeloblastic leukemia (AML)] were enrolled between January 2017 and June 2022 and underwent repeated small-volume exchange transfusion. The following were measured: demographic and clinical characteristics, time of the procedure, PWBC (peripheral white blood cell) count, hemoglobin, platelet count, blood biochemistry, electrolytes, coagulation, leukostasis, TLS (tumor lysis syndrome), DIC (disseminated intravascular coagulopathy), adverse events (AEs), and serious AEs (SAEs). Results: The demographic and clinical characteristics were not significantly different between ALL and AML patients, but differences were observed in PWBC counts (424.2 ± 135.6 vs. 223.8 ± 58.0 × 109/L). The procedures needed 3-8 processes, and the average procedure time was not significantly different between ALL and AML. The PWBC count gradually reduced to <100 × 109/L; hemoglobin, platelet count, K+, Na+, and Ca2+ were unchanged. Alanine aminotransferase, aspartate aminotransferase, total bilirubin, blood urea nitrogen, creatinine, troponin-I, creatine kinase-MB, prothrombin time, and activated partial thromboplastin time maintained normal or recovered from abnormal ranges. The manifestations of leukostasis, TLS, and DIC improved or disappeared. No AEs and SAEs occurred. The required total blood volume was based on initial PWBC count, manifestations of leukostasis, and age. Conclusions: Our finding suggests that repeated small-volume exchange transfusion is effective and safe for treating hyperleukocytosis in children with acute leukemia.

High-Sensitivity and Fast-Speed UV Photodetectors Based on Asymmetric Nanoporous-GaN/Graphene Vertical Junction.

GaN-based photodetectors are strongly desirable in many advanced fields, such as space communication, environmental monitoring, etc. However, the slow photo-response speed in currently reported high-sensitivity GaN-based photodetectors still hinders their applications. Here, we demonstrate a high-sensitivity and fast-speed UV photodetector based on asymmetric Au/nanoporous-GaN/graphene vertical junctions. The nanoporous GaN-based vertical photodetector shows an excellent rectification ratio up to ∼105 at +4 V/-4 V. The photo-responsivity and specific detectivity of the device is up to 1.01 × 104 A/W and 7.84 × 1014 Jones, respectively, more than three orders of magnitude higher than the control planar photodetector. With switching light on and off, the repeatable on/off current ratio of the nanoporous GaN-based vertical photodetector is ∼4.32 × 103, which is about 1.51 × 103 times to that of the control planar device. The measured rise/decay time is 12.2 µs/14.6 µs, which is the fastest value for the high-sensitivity GaN-based photodetectors to date. These results suggest that the asymmetric Au/nanoporous-GaN/graphene structure can improve the sensitivity and the photo-response speed of GaN-based PDs simultaneously.

Large and tunable magnetoresistance in van der Waals ferromagnet/semiconductor junctions.

Magnetic tunnel junctions (MTJs) with conventional bulk ferromagnets separated by a nonmagnetic insulating layer are key building blocks in spintronics for magnetic sensors and memory. A radically different approach of using atomically-thin van der Waals (vdW) materials in MTJs is expected to boost their figure of merit, the tunneling magnetoresistance (TMR), while relaxing the lattice-matching requirements from the epitaxial growth and supporting high-quality integration of dissimilar materials with atomically-sharp interfaces. We report TMR up to 192% at 10 K in all-vdW Fe3GeTe2/GaSe/Fe3GeTe2 MTJs. Remarkably, instead of the usual insulating spacer, this large TMR is realized with a vdW semiconductor GaSe. Integration of semiconductors into the MTJs offers energy-band-tunability, bias dependence, magnetic proximity effects, and spin-dependent optical-selection rules. We demonstrate that not only the magnitude of the TMR is tuned by the semiconductor thickness but also the TMR sign can be reversed by varying the bias voltages, enabling modulation of highly spin-polarized carriers in vdW semiconductors.

Current-assisted magnetization reversal in Fe3GeTe2 van der Waals homojunctions.

Among the numerous two-dimensional van der Waals (vdW) magnetic materials, Fe3GeTe2 (FGT), due to its outstanding properties such as metallicity, high Curie temperature and strong perpendicular magnetic anisotropy, has quickly emerged as a candidate with the most potential for the fabrication of all-vdW spintronic devices. Here, we fabricated a simple vertical homojunction based on two few-layer exfoliated FGT flakes. Under a certain range of external magnetic fields, the magnetization reversal can be achieved by applying a negative or positive pulse current, which can reduce the coercivity through the spin orbit torque of FGT itself in addition to the Joule heat. Moreover, the asymmetrical switching current is caused by the spin transfer torque in the homojunction. As the temperature increases, the magnetization reversal can be observed at a smaller external magnetic field. Our demonstrations of the current-assisted magnetization reversal under a magnetic field in all-vdW structures may provide support for the potential application of vdW magnetism.

Molecular Mechanism of the ß-Lactamase Mediated ß-Lactam Antibiotic Resistance of Pseudomonas aeruginosa Isolated From a Chinese Teaching Hospital.

Pseudomonas aeruginosa can cause infections in the blood, lungs (pneumonia), or other parts of the body after surgery. To investigate the molecular characteristics of ß-lactam antibiotic resistance of P. aeruginosa isolated from a hospital population between 2015 and 2017, in this study, the antimicrobial susceptibility and the resistance gene profile of the bacteria were determined. The Pulsed-field gel electrophoresis (PFGE) was used to characterize the clonal relatedness and sequencing and comparative genomic analysis were performed to analyze the structure of the resistance gene-related sequences. As a result, of the 260 P. aeruginosa strains analyzed, the resistance rates for 6 ß-lactam antibiotics ranged from 4.6 to 9.6%. A total of 7 genotypes of 44 ß-lactamase genes were identified in 23 isolates (8.9%, 23/260). Four transconjugants from different donors carrying bla CARB-3 exhibited a phenotype of reduced susceptibility to piperacillin-tazobactam, ceftazidime, and cefepime, and 2 transconjugants harboring bla IMP-45 exhibited a phenotype of reduced susceptibility to carbapenems. bla CARB positive isolates (n = 12) presented six PFGE patterns, designated groups A to F. Two bla genes (bla IMP-45 and bla OXA-1) in PA1609 related to a class 1 integron (intI1-bla IMP-45- bla OXA-1-aac(6')-Ib7-catB3-qacE∆1-sul1) were encoded on a plasmid (pPA1609-475), while the bla CARB-3 gene of PA1616 also related to a class 1 integron was located on the chromosome. The results suggest that ß-lactam antibiotic resistance and clonal dissemination exist in this hospital population. It indicates the necessity for molecular surveillance in tracking ß-lactamase-producing strains and emphasizes the need for epidemiological monitoring.

Colistin Resistance and Molecular Characterization of the Genomes of mcr-1-Positive Escherichia coli Clinical Isolates.

Research on resistance against polymyxins induced by the mcr-1 gene is gaining interest. In this study, using agar dilution method, polymerase chain reaction, and comparative genomic analysis, we investigated the colistin resistance mechanism of clinical E. coli isolates. The minimum inhibitory concentration (MIC) analysis results revealed that of the 515 isolates tested, bacteria with significantly increased MIC levels against colistin were isolated in 2019. Approximately one-fifth (17.14% to 19.65%) of the isolates showed MIC values ≥1 mg/L against colistin in 2015, 2016, and 2017. However, in 2019, up to three-quarters (74.11%, 146/197) of the isolates showed MIC values ≥1 mg/L against colistin indicating an increase in colistin resistance. Six isolates (EC7518, EC4968, EC3769, EC16, EC117, EC195, 1.13%, 6/515) were found to carry the mcr-1 gene and a novel mcr-1 variant with Met2Ile mutation was identified in EC3769. All six strains showed higher MIC levels (MIC=4 mg/L) than any mcr-1-negative strains (MIC ≤ 2 mg/L). Whole-genome sequencing of the six mcr-1-positive isolates revealed that EC195 carried the highest number of resistance genes (n = 28), nearly a half more than those of the following EC117 (n = 19). Thus, EC195 showed a wider resistance spectrum and higher MIC levels against the antimicrobials tested than the other five isolates. Multi-locus sequence typing demonstrated that these mcr-1-positive strains belonged to six different sequence types. The six mcr-1 genes were located in three different incompatibility group plasmids (IncI2, IncHI2 and IncX4). The genetic context of mcr-1 was related to a sequence derived from Tn6330 (ISApl1-mcr-1-pap2-ISApl1). Investigations into the colistin resistance mechanism and characterization of the molecular background of the mcr genes may help trace the development and spread of colistin resistance in clinical settings.

Identification of a novel aminoglycoside O-nucleotidyltransferase AadA33 in Providencia vermicola.

A novel chromosome-encoded aminoglycoside O-nucleotidyltransferase AadA33 was identified in Providencia vermicola strain P13. The AadA33 shares the highest amino acid identity of 51.28% with the function characterized AadA31. Antibiotic susceptibility testing and enzyme kinetics analysis revealed that the function of AadA33 is to mediate spectinomycin and streptomycin resistance. The recombinant strain harboring aadA33 (pUCP20-aadA33/Escherichia coli DH5α) displayed >256- and 128-fold increases in the minimum inhibitory concentration levels to spectinomycin and streptomycin, respectively, compared with the control strains pUCP20/DH5α. Enzyme kinetic parameters manifested the substrate of AadA33 including spectinomycin and streptomycin, with k cat/K m of 3.28 × 104 (M-1 s-1) and 3.37 × 104 (M-1 s-1), respectively. Bioinformatics analysis revealed its structural mechanism of antimicrobial resistance, genetic context, and phylogenetic relationship with other aminoglycoside O-nucleotidyltransferases. This study of AadA33 contributed to understanding the function and resistance mechanism of aminoglycoside O-nucleotidyltransferase.