Tumor-derived Prevotella intermedia aggravates gastric cancer by enhancing Perilipin 3 expression.

The indigenous microbial milieu within tumorous tissues exerts a pivotal influence on the genesis and advancement of gastric cancer (GC). This investigation scrutinizes the functions and molecular mechanisms attributed to Prevotella intermedia in the malignant evolution of GC. Isolation of P. intermedia from paired GC tissues was undertaken. Quantification of P. intermedia abundance in 102 tissues was accomplished using quantitative real-time PCR (qRT-PCR). Assessment of the biological effects of P. intermedia on GC cells was observed using culture medium supernatant. Furthermore, the protein profile of GC cells treated with tumor-derived P. intermedia was examined through label-free protein analysis. The functionality of perilipin 3 (PLIN3) was subsequently confirmed using shRNA. Our investigation revealed that the relative abundance of P. intermedia in tumor tissues significantly surpassed that of corresponding healthy tissues. The abundance of P. intermedia exhibited correlations with tumor differentiation (p = 0.006), perineural invasion (p = 0.004), omentum majus invasion (p = 0.040), and the survival duration of GC patients (p = 0.042). The supernatant derived from tumor-associated P. intermedia bolstered the proliferation, clone formation, migration, and invasion of GC cells. After indirect co-cultivation with tumor-derived P. intermedia, dysregulation of 34 proteins, including PLIN3, was discerned in GC cells. Knockdown of PLIN3 mitigated the malignancy instigated by P. intermedia in GC cells. Our findings posit that P. intermedia from the tumor microenvironment plays a substantial role in the malignant progression of GC via the modulation of PLIN3 expression. Moreover, the relative abundance of P. intermedia might serve as a potential biomarker for the diagnosis and prognosis of GC.

In vitro activity of meropenem-vaborbactam plus aztreonam against metallo-ß-lactamase-producing Klebsiella pneumoniae.

We evaluated the in vitro activity of meropenem-vaborbactam plus aztreonam (MEV-ATM) against 140 metallo-ß-lactamase (MBL)-producing Klebsiella pneumoniae isolates. Among them, 25 isolates (17.9%) displayed minimum inhibitory concentrations (MIC) ≥ 8 µg/mL, while 112 (80.0%) had MIC ≤ 2 µg/mL. Genomic analysis and subsequent gene cloning experiments revealed OmpK36 134-135GD-insertion and increased carbapenemase gene (blaNDM-1 and blaOXA-48-like) copy numbers are the main factors responsible for MEV-ATM non-susceptibility. Notably, MEV-ATM is actively against aztreonam-avibactam-resistant mutants due to CMY-16 mutations.

Identification of TMexCD-TOprJ-producing carbapenem-resistant Gram-negative bacteria from hospital sewage.

Carbapenems and tigecycline are crucial antimicrobials for the treatment of gram-negative bacteria infections. Recently, a novel resistance-nodulation-division (RND) efflux pump gene cluster, tmexCD-toprJ, which confers resistance to tigecycline, has been discovered in animals and clinical isolates. It was reported that hospital sewage could act as a reservoir for gram-negative bacteria with high antimicrobial resistance genes. In this study, we analyzed 84 isolates of carbapenem-resistant gram-negative bacteria (CR-GNB) from hospital sewage, and identified five isolates of TMexCD-ToprJ-producing CR-GNB, including one Raoultella ornithinolytica isolate and four Pseudomonas spp. isolates. All these five isolates carried at least one carbapenem resistance gene and were resistant to multiple antibiotics. Multiple tmexCD-toprJ clusters were detected, including tmexC2D2-toprJ2, tmexC3D3-toprJ3, tmexC3.2D3.3-toprJ1b and tmexC3.2D3-toprJ1b. Among these clusters, the genetic construct of tmexC3.2D3-toprJ1b showed 2-fold higher minimum inhibitory concentration (MIC) of tigecycline than other three variants. In addition, it was found that the tmexCD-toprJ gene cluster was originated from Pseudomonas spp. and mainly located on Tn6855 variants inserted in the same umuC-like genes on chromosomes and plasmids. This unit co-localized with blaIMP or blaVIM on IncHI5-, IncpJBCL41- and IncpSTY-type plasmids in the five isolates of TMCR-GNB. The IncHI5- and IncpSTY-type plasmids had the ability to conjugal transfer to E. coli J53 and P. aeruginosa PAO1, highlighting the potential risk of transfer of tmexCD-toprJ from Pseudomonas spp. to Enterobacterales. Importantly, genomic analysis showed that similar tmexCD-toprJ-harboring IncHI5 plasmids were also detected in human samples, suggesting transmission between environmental and human sectors. The emergence of TMCR-GNB from hospital sewage underscores the need for ongoing surveillance of antimicrobial resistance genes, particularly the novel resistance genes such as the tmexCD-toprJ gene clusters in the wastewater environment.

Metal-Free Atom Transfer Radical Polymerization to Prepare Recylable Micro-Adjuvants for Dendritic Cell Vaccine.

In the development of dendritic cell (DC) vaccines, the maturation of DCs is a critical stage. Adjuvants play a pivotal role in the maturation of DCs, with a major concern being to ensure both efficacy and safety. This study introduces an innovative approach that combines high efficacy with safety through the synthesis of micro-adjuvants grafted with copolymers of 2-(methacrylamido) glucopyranose (MAG) and methacryloxyethyl trimethyl ammonium chloride (DMC). The utilization of metal-free surface-initiated atom transfer radical polymerization enables the production of safe and recyclable adjuvants. These micrometer-sized adjuvants surpass the optimal size range for cellular endocytosis, enabling the retrieval and reuse of them during the ex vivo maturation process, mitigating potential toxicity concerns associated with the endocytosis of non-metabolized nanoparticles. Additionally, the adjuvants exhibit a "micro-ligand-mediated maturation enhancement" effect for DC maturation. This effect is influenced by the shape of the particle, as evidenced by the distinct promotion effects of rod-like and spherical micro-adjuvants with comparable sizes. Furthermore, the porous structure of the adjuvants enables them to function as cargo-carrying "micro-shuttles", releasing antigens upon binding to DCs to facilitate efficient antigen delivery.

Rumination and the default mode network: Meta-analysis of brain imaging studies and implications for depression.

Rumination is strongly and consistently correlated with depression. Although multiple studies have explored the neural correlates of rumination, findings have been inconsistent and the mechanisms underlying rumination remain elusive. Functional brain imaging studies have identified areas in the default mode network (DMN) that appear to be critically involved in ruminative processes. However, a meta-analysis to synthesize the findings of brain regions underlying rumination is currently lacking. Here, we conducted a meta-analysis consisting of experimental tasks that investigate rumination by using Signed Differential Mapping of 14 fMRI studies comprising 286 healthy participants. Furthermore, rather than treat the DMN as a unitary network, we examined the contribution of three DMN subsystems to rumination. Results confirm the suspected association between rumination and DMN activation, specifically implicating the DMN core regions and the dorsal medial prefrontal cortex subsystem. Based on these findings, we suggest a hypothesis of how DMN regions support rumination and present the implications of this model for treating major depressive disorder characterized by rumination.

The subsystem mechanism of default mode network underlying rumination: A reproducible neuroimaging study.

Rumination is a repetitive self-referential thinking style that is often interpreted as an expression of abnormalities of the default mode network (DMN) observed during "resting-state" in major depressive disorder (MDD). Recent evidence has demonstrated that the DMN is not unitary but can be further divided into 3 functionally heterogenous subsystems, although the subsystem mechanistically underlying rumination remains unclear. Due to the unconstrained and indirect correlational nature of previous resting-state fMRI studies on rumination's network underpinnings, a paradigm allowing direct investigation of network interactions during active rumination is needed. Here, with a modified continuous state-like paradigm, we induced healthy participants to ruminate or imagine objective scenarios (distraction, as a control condition) on 3 different MRI scanners. We compared functional connectivities (FC) of the DMN and its 3 subsystems between rumination and distraction states. Results yielded a highly reproducible and dissociated pattern. During rumination, within-DMN FC was generally decreased as compared to the distraction state. At the subsystem level, we found increased FC between the core and medial temporal lobe (MTL) subsystem as well as decreased FC between the core and dorsal medial prefrontal cortex (DMPFC) subsystem and within the MTL subsystem. Finally, subjects' behavioral measures of rumination and brooding were negatively correlated with FC between the core and DMPFC subsystems. These results suggest active rumination involves enhanced constraint by the core subsystem on the MTL subsystem and decreased coupling between the core and DMPFC subsystem, allowing for more information exchange among those involved DMN components. Furthermore, the reproducibility of our findings provides a rigorous evaluation of their validity and significance.

Emergence of colistin-heteroresistant and carbapenem-resistant hypervirulent Klebsiella pneumoniae.

OBJECTIVES: To investigate the clinical emergence of colistin-heteroresistant, hypervirulent, and multidrug-resistant Klebsiella pneumoniae, and characterize the underlying molecular mechanisms. METHODS: The population analysis profiles (PAPs) method was used to detect colistin heteroresistance. The time-killing assay was used to examine the effect of colistin on carbapenem-resistant Klebsiella pneumoniae (CRKP) in vitro. Galleria mellonella larvae infection model was used to test the potential virulence. qRT-PCR assay was conducted to compare the expression levels of efflux pump genes. Next and third-generation sequencing were conducted to analyse the genomic features. RESULTS: Two colistin-heteroresistant isolates were detected from a multi-center carbapenem-resistant Enterobacterales (CRE) surveillance study in China, which exhibited similar survival rates as the K2 hypervirulent reference strain ATCC 43816 in a G. mellonella larvae model. The two isolates belonged to ST11, harbouring the iucABCD, iutA, iroBCD, and rpmA2 hypervirulent genes and pLVPK-like virulence plasmids. Colistin showed a weak effect on the heteroresistant strains in vitro. The efflux pump genes acrA, acrB, tolC, oqxA, and oqxB were upregulated in this subpopulation compared to the parental strains. CONCLUSIONS: This study showed the clinical emergence of colistin-heteroresistant, hypervirulent, and multidrug-resistant Klebsiella pneumoniae. AcrAB-TolC and OqxAB efflux overexpression were involved in mediating colistin heteroresistance.

Emergence of Aeromonas veronii strain co-harboring blaKPC-2, mcr-3.17, and tmexC3.2-tmexD3.3-toprJ1b cluster from hospital sewage in China.

Introduction: The raise of multi-drug resistant bacteria involving carbapenem, colistin, or tigecycline resistance constitutes a threat to public health, which partly results from the transmission of corresponding mobile resistance genes, such as blaKPC and blaNDM for carbapenem, mcr for colistin, and tmexCD-toprJ gene cluster for tigecycline. Herein, we described the emergence of an Aeromonas veronii strain HD6454 co-harboring blaKPC-2, mcr-3.17, and tmexC3.2-tmexD3.3-toprJ1b gene cluster from hospital sewage. Methods: Whole genome sequencing (WGS) was used to determine the genome sequence of HD6454, and the detailed genomic analysis of genetic elements or regions carrying key antimicrobial resistance genes (ARGs) from HD6454 were performed. Cloning experiment was conducted to confirm the function of key ARGs in mediating antimicrobial resistance. Conjugation experiment was conducted to determine the mobility of the plasmid. Results: The results showed that this strain belonged to a novel sequence type (ST) variant ST1016, and carried 18 important ARGs. Among them, the blaKPC-2 was carried by non-self-transmissible IncP-6 plasmid, while tmexC3.2-tmexD3.3-toprJ1b gene cluster and mcr-3.17 were carried by integrative and mobilizable element (IME) or IME-related region in chromosome. The mcr-3.17, mcr-3.6, and mcr-3-like3 genes were further inferred to originate from IMEs of Aeromonas species. Additionally, for the first time, the mcr-3.17 was confirmed to confer low-level resistance to colistin under inducible expression, while tmexC3.2-tmexD3.3-toprJ1b gene cluster was confirmed to confer low-level resistance to tigecycline. Discussion: This is the first report of a strain co-harboring blaKPC-2, mcr-3.17, and tmexC3.2-tmexD3.3-toprJ1b gene cluster. Although the resistance and/or mobility of these ARGs are limited in this strain, the emergence of this multiple important ARGs-carrying strain deserves further attention.

How does ChatGPT-4 preform on non-English national medical licensing examination? An evaluation in Chinese language.

ChatGPT, an artificial intelligence (AI) system powered by large-scale language models, has garnered significant interest in healthcare. Its performance dependent on the quality and quantity of training data available for a specific language, with the majority of it being in English. Therefore, its effectiveness in processing the Chinese language, which has fewer data available, warrants further investigation. This study aims to assess the of ChatGPT's ability in medical education and clinical decision-making within the Chinese context. We utilized a dataset from the Chinese National Medical Licensing Examination (NMLE) to assess ChatGPT-4's proficiency in medical knowledge in Chinese. Performance indicators, including score, accuracy, and concordance (confirmation of answers through explanation), were employed to evaluate ChatGPT's effectiveness in both original and encoded medical questions. Additionally, we translated the original Chinese questions into English to explore potential avenues for improvement. ChatGPT scored 442/600 for original questions in Chinese, surpassing the passing threshold of 360/600. However, ChatGPT demonstrated reduced accuracy in addressing open-ended questions, with an overall accuracy rate of 47.7%. Despite this, ChatGPT displayed commendable consistency, achieving a 75% concordance rate across all case analysis questions. Moreover, translating Chinese case analysis questions into English yielded only marginal improvements in ChatGPT's performance (p = 0.728). ChatGPT exhibits remarkable precision and reliability when handling the NMLE in Chinese. Translation of NMLE questions from Chinese to English does not yield an improvement in ChatGPT's performance.

Epidemiological characteristics and molecular features of carbapenem-resistant Enterobacter strains in China: a multicenter genomic study.

Epidemiological characteristics and molecular features of carbapenem-resistant Enterobacter (CR-Ent) species remain unclear in China. In this study, we performed a genomic study on 92 isolates from Enterobacter-caused infections from a multicenter study in China. Whole genome sequencing (WGS) was used to determine the genome sequence of 92 non-duplicated CR-Ent strains collected from multiple tertiary health centres. The precise species of Enterobacter strains were identified by average nucleotide identity (ANI) and in silico DNA-DNA hybridization (isDDH). Molecular features of high-risk CR-Ent sequence type (ST) lineages and carbapenemase-encoding plasmids were determined. The result revealed that the most common human-source CR-Ent species in China was E. xiangfangensis (66/92, 71.93%), and the proportion of carbapenemase-producing Enterobacter (CP-Ent) in CR-Ent was high (72/92, 78.26%) in comparison to other global regions. Furthermore, ST171 and ST116 E. xiangfangensis were the major lineages of CP-Ent strains, and ST171 E. xiangfangensis was more likely to cause infections in older patients. Genomic analysis also highlighted the likelihood of intra-hospital/inter-hospital clonal transmission of ST171 and ST116 E. xiangfangensis. In addition, the blaNDM-harbouring IncX3-type plasmid was identified as the prevalent carbapenemase-encoding plasmid carried by CR-Ent strains, and was experimentally confirmed to be able to self-transfer with high frequency. This study detailed the genomic and clinical characteristics of CR-Ent in China in the form of multicenter for the first time. The high risk of carbapenemase-producing ST171 and ST116 E. xiangfangensis, and the blaNDM-harbouring IncX3-type plasmid were detected and emphasized.

Analysis of a Refractory Case of Pediatric Meningitis Caused by Klebsiella pneumoniae Co-Resistant to Carbapenems and Polymyxins.

We report our clinical exploration experience treating a 6-year-old girl with a postoperative central nervous system (CNS) infection of prolonged invasion with Klebsiella pneumoniae (K. pneumoniae) co-resistant to carbapenems and polymyxin B. Although rational antibiotic therapy and effective source control measures were applied, the infection was not controlled eventually. To understand the mechanism of infection, whole-genome sequencing (WGS) was used to explore the resistance mechanism, and the susceptibility test was used to observe the efficacy of ceftazidime-avibactam (CAZ-AVI) in vitro. It is currently uncertain whether CAZ-AVI could be used as a salvage therapy for pediatric CNS infection. Therefore, we hope to share this case to seek medical help worldwide to treat pediatric CNS infection.

The Role of the Two-Component QseBC Signaling System in Biofilm Formation and Virulence of Hypervirulent Klebsiella pneumoniae ATCC43816.

Hypervirulent Klebsiella pneumoniae (hvKP) is an evolving infectious pathogen associated with high mortality. The convergence of hypervirulence and multidrug resistance further challenges the clinical treatment options for K. pneumoniae infections. The QseBC two-component system (TCS) is a component of quorum-sensing regulatory cascade and functions as a global regulator of biofilm growth, bacterial motility, and virulence in Escherichia coli. However, the functional mechanisms of QseBC in hvKP have not been reported, and we aim to examine the role of QseBC in regulating virulence in hvKP strain ATCC43816. The CRISPR-Cas9 system was used to construct qseB, qseC, and qseBC knockout in ATCC43816. No significant alterations in the growth and antibiotic susceptibility were detected between wild-type and mutants. The deletion of qseC led to an increase of biofilm formation, resistance to serum killing, and high mortality in the G. mellonella model. RNAseq differential gene expression analysis exhibited that gene-associated biofilm formation (glgC, glgP, glgA, gcvA, bcsA, ydaM, paaF, ptsG), bacterial type VI secretion system (virB4, virB6, virB10, vgrG, hcp), and biosynthesis of siderophore (entC, entD, entE) were significantly upregulated in comparison with the wild-type control. In addition, qseB, ygiW (encode OB-family protein), and AraC family transcriptional regulator IT767_23090 genes showed highest expressions in the absence of QseC, which might be related to increased virulence. The study provided new insights into the functional importance of QseBC in regulating the virulence of hvKP.

blaKPC-24-Harboring Aeromonas veronii from the Hospital Sewage Samples in China.

KPC-24, different from KPC-2 by a single amino acid alteration at codon 6 (R6P), was initially discovered in Klebsiella pneumoniae in Chile. Here, we reported KPC-24-producing Aeromonas veronii isolates from hospital sewage in China. The blaKPC-24 was cloned and the MICs were tested against ß-lactams antimicrobial agents. KPC-24 exhibited a ß-lactam susceptibility profile similar to that of KPC-2. Whole-genome sequencing and analysis revealed that blaKPC-24 was located within a Tn6296-related region on an IncP-6 plasmid. IMPORTANCE Our study described a variant of K. pneumoniae carbapenemase (KPC), KPC-24, from two A. veronii strains isolated from hospital sewage, in which antibiotics, biocides, pharmaceuticals, and heavy metals may supply an appropriate condition for the evolution of carbapenemases. Some variants exhibited stronger hydrolysis activity to antibiotics and gave rise to a major public health concern. More seriously, Aeromonas species are prevalent in aquatic environments and, thus, may act as a suitable vector for antibiotics-resistance genes and foster the transmission of resistance. We should attach importance to surveying the evolution and transmission of antibiotics-resistance genes.

NDM-1 and OXA-48-Like Carbapenemases (OXA-48, OXA-181 and OXA-252) Co-Producing Shewanella xiamenensis from Hospital Wastewater, China.

Background: Shewanella genus, as an important carrier of resistance genes, has the potential to transmit resistance to many antimicrobials in many circumstances, especially in aquatic environment. The aim of the study was to describe the risk of Shewanella xiamenensis in hospital environment through analysis of genomic comparison and resistance status. Methods: Seven S. xiamenensis strains were isolated from hospital wastewater. PCR and Sanger sequencing were carried out for detection of common carbapenemase genes. Antimicrobial susceptibility testing was performed to determine the antimicrobial profile. Whole genome sequencing was applied, and sequences were further used for genomic analysis. Results: Seven Shewanella xiamenensis were all positive for bla NDM and bla OXA-48. Antimicrobial susceptibility testing showed all Shewanella xiamenensis were resistant to cefotaxime, ceftazidime, imipenem, meropenem, gentamycin and trimethoprim-sulfamethoxazole. Whole genome sequencing and phylogenetic analysis demonstrated the diversity of Shewanella xiamenensis despite isolating from one wastewater pool. Conclusion: To the best of our knowledge, this is the first report of detection of three types bla OXA-48-like genes in one hospital in China. And we have detected multi-drug resistant S. xiamenensis from hospital wastewater. This emphasizes that the presence of naturally existing carbapenemases in the environment may be significantly overlooked and that the bla OXA-48-like genes in China may originate through the horizontal gene transfer from S. xiamenensis to Enterobacterales rather than import from other countries.

Emerging and re-emerging KPC-producing hypervirulent Pseudomonas aeruginosa ST697 and ST463 between 2010 and 2021.

Carbapenem-resistant Pseudomonas aeruginosa (CRPA) has been a major threat to human health due to its increased morbidity and mortality in clinical settings. Carbapenemase genes are less frequently found in CRPA compared with carbapenem-resistant Enterobacterales, of which carbapenemase producers are common. In this study, we identified 11 blaKPC-2-harbouring P. aeruginosa isolates from 139 carbapenemase-insensitive P. aeruginosa isolates collected between 2010 and 2021 in a tertiary hospital in China. Nine isolates belonged to ST697, while the other two were ST463. The antibiotic susceptibility testing showed that all the isolates were multidrug resistant, including resistance to imipenem, meropenem, ceftazidime, and tigecycline. Patients with Klebsiella pneumoniae carbapenemase-2 (KPC-2)-producing P. aeruginosa infections were mostly associated with complicated diseases and prolonged hospital stay, with 30% deterioration. The whole-genome sequencing analysis showed that these isolates carried multiple antibiotic resistance genes and virulence genes, and the KPC-2 genetic elements were highly related in ST697 isolates. The complete sequencing of ST697 isolate SE5416 showed that the harbouring of blaKPC-2 resulted from complex transposition and homologous recombination of an IncpRBL16 plasmid and other mobile elements. The Galleria mellonella infection model experiment showed that these KPC-2-producing P. aeruginosa-infected larvae had low survival rates and high virulence. The present study revealed the shifting of CRPA from ST697 to ST463 in East China; ST463 had higher drug resistance, posing greater challenges for clinical management.

DANMEL: A manually curated reference database for analyzing mobile genetic elements associated with bacterial drug resistance.

We have developed a manually curated online reference database, DANMEL (http://124.239.252.254/danmel/), that addresses the lack of accurate dissection and annotation of the genetic structures of mobile genetic elements (MGEs) with genes for drug resistance. DANMEL contains accurately annotated and genetically dissected reference MGEs covering 5 categories and 135 subcategories/subfamilies of MGEs. Further, DANMEL provides a detailed guide on how to precisely annotate MGEs. DANMEL also provides SEARCH/BLAST functions to facilitate finding reference MGEs. Overall, DANMEL will aid researchers to conduct in-depth genetic analysis of sequenced bacterial MGEs with drug-resistance genes and further facilitate a better understanding of bacterial MGEs associated with drug resistance at a genomic level.

Polyelectrolyte multilayers of diblock copolymer micelles with temperature-responsive cores.

We report on assembly and stimuli-response behavior of layer-by-layer (LbL) films of pH- and temperature-responsive cationic diblock copolymer micelles (BCMs) of poly(2-(dimethylamino)ethyl methacrylate)-block-poly(N-isopropylacrylamide) (PDMA-b-PNIPAM) and a linear polyanion polystyrene sulfonate (PSS). As a function of solution pH at temperatures above lower critical solution temperature (LCST) of PNIPAM, PDMA-b-PNIPAM micelles have been demonstrated earlier to exhibit an abrupt change in micellar aggregation number and hydrodynamic size between larger and smaller BCMs (LBCMs and SBCMs, respectively). Here, LBCMs or SBCMs were included within LbL films through self-assembly with a polyanion, and film pH and temperature responses were studied using ellipsometry and atomic force microscopy (AFM). Both types of micelle preserved their micellar morphology when adsorbed at the surface of oxidized silicon wafers coated with PSS-terminated precursor layer at a constant pH. Response of adsorbed BCMs to temperature and pH variations was strongly dependent on whether or not BCMs were coated with the PSS layer. While monolayers of LBCMs lost their original dry morphology in response to pH or temperature variations, depositing a PSS layer atop LBCMs inhibited such irreversible restructuring. As a result of wrapping around and strong binding of PSS chains with LBCM micelles, BCM/PSS assemblies preserved their original dry state morphology despite the application of pH and temperature triggers. However, the wet-state film response to pH and temperature stimuli was drastically different. Swelling of BCM/PSS multilayers was strongly affected by temperature but was almost independent of pH due to neutralization of BCM PDMA's coronal charge with PSS. Cycling the temperature below and above PNIPAM's LCST caused PNIPAM chains within BCM cores to swell or collapse, resulting in reversible swelling transitions in the entire BCM/PSS assemblies. Temperature-controlled switching between the hydrophobic and hydrophilic state of assembled micellar cores was also used to regulate the release of a micelle-loaded hydrophobic pyrene dye, whose release rate increased at temperatures below PNIPAM's LCST.

Identification of a Novel blaNDM Variant, blaNDM-33, in an Escherichia coli Isolate from Hospital Wastewater in China.

Since the discovery of NDM-1 and the worldwide reporting of different variants have raised alarms concerning global health, the problem of carbapenem-resistant Enterobacterales (CRE) has become increasingly serious. Therefore, research on the hydrolytic activity and molecular structure of NDM variants is beneficial to the development of antibacterial drugs. NDM has been evolving into variants that possess different hydrolysis activities toward ß-lactam antibiotics. Here, we characterized a novel blaNDM variant, named blaNDM-33, identified from a multidrug-resistant Escherichia coli strain from hospital sewage. NDM-33 differed from NDM-5 with a single-amino-acid substitution (A72T). blaNDM-5 was located in the Tn125-related blaNDM-33 region from an IncX3-type plasmid, pHD6415-NDM, that can be transferred horizontally. The genetic construct of blaNDM-33 showed higher MICs of carbapenems than a blaNDM-5 construct. Enzyme kinetics showed that NDM-33 had higher enzymatic activity for meropenem and cefazolin than NDM-5. The emergence of this novel NDM variant could pose a threat to public health because of its transferability and enhanced carbapenem activity. IMPORTANCE Our study described a novel NDM-33 variant from an E. coli strain isolated from hospital sewage, where it was associated with human disease and antibiotic exposure. Importantly, hospital sewage was increasingly considered to be related to CRE hosts. Pathogens were transmitted from reservoirs through direct and indirect contact, ingestion, and inhalation of contaminated water or aerosols. In addition, under the selective pressure of antibiotics, NDM variants will become the main strain in the hospital water system and evolve into high virulence and high resistance. The monitoring of NDM mutants is of great significance for preventing and controlling the evolution of superbugs.

Emergence and genomics of OXA-232-producing Klebsiella pneumoniae in a hospital in Yancheng, China.

OBJECTIVES: The aims of this study were to infer the phylogenetic relationship of OXA-232-producing Klebsiella pneumoniae (OXA232Kp) strains collected from a Chinese hospital and to determine the composition and genetic background of antimicrobial resistance genes (ARGs) among these strains. METHODS: Three non-duplicate OXA232Kp strains were collected from a Chinese hospital. Whole-genome sequencing was used to determine their genome sequences and then a genomic comparison of ARG-carrying genetic elements from the three strains with related sequences was performed. Phylogenetic analysis was conducted by constructing a maximum-likelihood phylogenetic tree. RESULTS: Compared with other Chinese sequence type 15 (ST15)-OXA232Kp strains, the three ST15-OXA232Kp strains in this study could be divided into a single subgroup in phylogenetic relationship. The composition and genetic background of ARGs were identical in the three strains. Three ARG-carrying genetic elements or multidrug resistance (MDR) regions were determined, including a truncated Tn2013-like IS-based transposition unit, a unit transposition Tn6867b and a 40.9-kb MDR region. CONCLUSION: This study reported clonal dissemination of ST15-OXA232Kp strains carrying multiple ARGs in a Chinese hospital. A comprehensive evolutionary and genomics analysis provided a deeper understanding of OXA232Kp. Further surveillance and study should be advocated to prevent the dissemination of OXA232Kp strains in China.

Diversification and prevalence of the quinolone resistance crpP genes and the crpP-carrying Tn6786-related integrative and conjugative elements in Pseudomonas aeruginosa.

The quinolone resistance crpP genes can mediate decreased susceptibility to quinolones. However, diversification and prevalence of crpP genes and crpP-carrying integrative and conjugative elements (ICEs) still need to be elucidated. In this study, genome sequencing was conducted for 200 Chinese Pseudomonas aeruginosa isolates, 16 of which were fully sequenced. All the 37 available CrpP variants were collected for phylogenetic analysis, 10 CrpP enzymes were chosen to conduct cloning and antimicrobial susceptibility test, and 22 crpP-carrying Tn6786-related ICEs were selected for detail genetic dissection analysis. Then, typing/nomenclature schemes for crpP variants and crpP-carrying ICEs were established for the first time. The 10 representative CrpP enzymes were confirmed to mediate decreased susceptibility to one to three quinolones. Tn6786-related ICEs displayed high-level diversification in both nucleotide sequences and modular structures. Mainly, massive gene acquisition/loss occurred across the whole genomes of Tn6786-related ICEs. 53.5% (107/200) of the tested clinical P. aeruginosa isolates from China carried crpP genes, which were exclusively located within chromosome-borne Tn6786-related ICEs. The crpP-carrying ICEs were at active stages of evolution and had the high potential to be an important vector for the dissemination of resistance genes besides crpP. The present study furthered the understanding of the bioinformatics and epidemiology of crpP genes and crpP-carrying ICEs.