Objective:Urinary tract infection (UTI) is a major health concern in pediatric populations. By analysing temporal changes in pathogen distribution and antimicrobial resistance among children with UTIs in Southwest China from 2020 to 2024, we aim to provide a robust scientific basis for the empirical antibiotic therapy in this region. Methods:We retrospectively analyzed non-duplicate pathogens isolated from urine specimens and their antimicrobial susceptibility results in 6598 children (≤14 years old) diagnosed with UTIs in southwest China from 2020 to 2024. These results were interpreted according to the M100 guidelines of the American Clinical and Laboratory Standards Institute (CLSI) and analysed using WHONET 5.6 software. Results:A total of 7831 strains of pathogenic bacteria were detected, of which 60.1% were gram-negative and 39.9% were gram-positive. The top five bacteria detected were Escherichia coli (37.8%), Enterococcus faecium (26.3%), Enterococcus faecalis (7.5%), Klebsiella pneumoniae (6.9%) and Pseudomonas aeruginosa (2.5%). E. coli showed less than 10% resistance to piperacillin/tazobactam, cefoperazone/sulbactam, amikacin and nitrofurantoin, with resistance to quinolones ranging from 31.3% to 51.5%. K. pneumoniae showed resistance rates of 13.1% and 16.8% to imipenem and meropenem, respectively, from 2020 to 2024. E. faecium showed significantly higher resistance rates to the tested drugs than E. faecalis, particularly to ampicillin (95.1-97.4% vs 4.9-8.0%). Methicillin-resistant Staphylococcus aureus (MRSA) was detected at a rate of 33.8%. MRSA showed a higher level of resistance to penicillin, rifampicin, levofloxacin, clindamycin and erythromycin than methicillin-sensitive strains. Conclusion:Over the past five years, the main pathogenic bacteria responsible for pediatric UTIs in southwestern China were E. coli, E. faecium and E. faecalis. Resistance patterns among major uropathogens revealed diverse trends, and the emergence of multidrug-resistant organisms presents a serious therapeutic challenge that warrants close surveillance.

The plasmid-mediated tigecycline resistance gene tmexCD1-toprJ1 and its variants have emerged as a public health threat, with increasing identification in various sources of Enterobacterales worldwide. However, comprehensive epidemiological features of tmexCD1-toprJ1 in clinical carbapenem-resistant Klebsiella pneumoniae (CRKP) remain limited. Herein, we conducted a retrospective nationwide surveillance to assess the prevalence and molecular epidemiology of clinical tmexCD1-toprJ1-positive isolates from 4314 non-duplicated CRKP strains collected from 151 medical institutions across 31 provinces, municipalities, and autonomous regions in China. tmexCD1-toprJ1 was detected in 18 (0.42%) CRKP strains spanning 12 provinces, all exhibiting multidrug resistance phenotypes. ST147 was the dominant sequence type and predominantly co-harbored blaKPC-2. Phylogenetic analysis unveils the intrahospital, interhospital, and interprovincial spread of tmexCD1-toprJ1 carrying ST147 CRKP, which display a closer genomic proximity to those from other global regions, suggesting the international transmission risk of tmexCD1-toprJ1. Variable tigecycline resistance levels among isogenic ST147 strains were associated with differential tmexCD1-toprJ1 expression. Further, three types of plasmid replicons were found in the carriage of tmexCD1-toprJ1, among which IncFIB(K) and IncFIB(K)/IncHI1B were the primary vectors of tmexCD1-toprJ1, and a multireplicon megaplasmid was identified. The emergence of regionally disseminated tmexCD1-toprJ1-bearing ST147 CRKP clone highlights the potential global spread risk of tmexCD1-toprJ1, underscoring the urgent need for further surveillance and control measures to mitigate the ongoing spread of this resistant pathogen.

Objective:Antimicrobial resistance (AMR) represents one of the most pressing global public health threats. This study aimed to analyze the distribution and antimicrobial resistance profiles of Carbapenem-resistant Gram-negative Bacteria (CRGNB) isolated from pediatric patients in Sichuan Province, China, in order to provide evidence to support rational antimicrobial use and infection prevention and control in clinical practice. Methods:This retrospective study included non-duplicate CRGNB isolates recovered from hospitalized children aged ≤14 years in 134 medical institutions across Sichuan Province from 2021 to 2025. Bacterial identification and antimicrobial susceptibility testing were performed according to a unified surveillance protocol. CRGNB was defined, in accordance with CLSI M100, 34th edition (2024), as isolates resistant to at least one carbapenem (imipenem, meropenem, or ertapenem). Data were analyzed using WHONET 5.6. Results:A total of 2523 CRGNB isolates were collected. Isolates from male patients accounted for 56.4% (1422/2523), and the largest proportion of isolates was from the 29 days to ≤1 year age group (41.8%, 1054/2523). The five most frequently isolated species were Klebsiella pneumoniae (41.8%, 1055/2523), Acinetobacter baumannii (22.1%, 558/2523), Escherichia coli (10.0%, 252/2523), Enterobacter cloacae complex (9.3%, 235/2523), and Pseudomonas aeruginosa (6.4%, 162/2523), with respiratory specimens accounting for most isolates (59.6%, 1504/2523). Enterobacterales showed susceptibility rates >96% to tigecycline and polymyxin B. K. pneumoniae showed 87.5% susceptibility to ceftazidime-avibactam. A. baumannii exhibited low resistance only to polymyxin B and tigecycline (2.3% and 2.5%, respectively). P. aeruginosa showed 100% susceptibility to ceftazidime-avibactam and polymyxin B. Conclusion:CRGNB infections among children in Sichuan Province remain severe and display marked regional characteristics, with infants constituting a high-risk population. The increasing prevalence of multidrug-resistant organisms poses a substantial challenge to clinical management and warrants close surveillance and targeted intervention.

Objectives We aimed to evaluate the effectiveness, safety, and pharmacokinetics of eravacycline in treating carbapenem-resistant organism (CRO) infections in immunocompromised hosts (ICHs). Methods A prospective study was conducted at five hospitals in China from January 2024 to July 2025. Patients with confirmed CRO infections who received intravenous eravacycline at a fixed, consecutive dose of 50 mg for at least 72 hours were included. Plasma concentrations were measured, and pharmacokinetic modeling was performed. Results Microbiological clearance rates differed by infection site: intra-abdominal infections showed the highest clearance (80.6%, 50/62) and pulmonary infections the lowest (32.4%, 23/71), compared with the overall cohort clearance rate of 51.4% (91/177) (P < 0.001). The 28-day mortality rate was 35.6%. PPK modeling (one-compartment), based on plasma concentration data from 80 patients (54 transplant and 26 non-transplant), revealed reduced clearance in non-transplant patients with cirrhosis, with 45.7% lower clearance in Child-Pugh B and 86.3% lower clearance in Child-Pugh C. In transplant recipients, body weight (BW) exhibited a significant linear association with clearance, while the C-reactive protein level was inversely correlated with distribution volume, while moderate CYP3A4/5 inhibitor use increased the volume by 38.9%. Adverse events occurred in 13.6% of patients. Multivariable analysis identified older age and fungal co-infection as factors associated with mortality. A treatment duration of ≥ 5 days was associated with improved survival. Conclusions Eravacycline monotherapy can achieve favorable outcomes in ICHs with CRO infections and help in managing future CRO infections.

Objective:To characterize the distribution and antimicrobial resistance patterns of pathogens causing bloodstream infections in elderly patients in Sichuan Province from 2020 to 2024. Methods:Non-duplicate isolates from blood of patients aged ≥65 years in 134 provincial medical institutions (113 tertiary, 21 secondary) were collected and tested per a unified protocol. Species identification and susceptibility were interpreted using CLSI M100 criteria. Data were analyzed with WHONET 5.6. The study period was stratified into pandemic (2020-2022) and post-pandemic (2023-2024) phases to assess effects on multidrug-resistant and pandrug-resistant organisms. Results:65,603 isolates were obtained from elderly patients' blood specimens, of which 23,350 (35.6%) were Gram-positive and 42,253 (64.4%) were Gram-negative. The five most frequently detected organisms were Escherichia coli (38.4%), Klebsiella pneumoniae (12.6%), Staphylococcus hominis (6.6%), Staphylococcus epidermidis (6.0%), and Staphylococcus aureus (5.8%). E. coli exhibited low carbapenem resistance (ertapenem 0.8%, imipenem 0.9%, meropenem 0.9%), whereas K. pneumoniae showed carbapenem resistance of 6.7-8.4%. Methicillin-resistant S. aureus and methicillin-resistant coagulase-negative staphylococci were detected at rates of 29.1% and 70.8%, respectively; no vancomycin-resistant staphylococci were identified. A total of 126 pandrug-resistant Acinetobacter baumannii (PDR-AB) isolates were identified, accounting for 11.2% (126/1124). No pandrug-resistant Enterobacterales or Pseudomonas aeruginosa were detected. In the post-pandemic period, the detection rates of carbapenem-resistant A. baumannii and carbapenem-resistant Klebsiella pneumoniae increased significantly compared with the pandemic period (P < 0.05). Conclusion:From 2020 to 2024, a diverse spectrum of bacterial species was isolated from bloodstream infections in elderly patients in Sichuan Province. Following the COVID-19 pandemic, the burden of carbapenem-resistant organisms increased. Region-specific antimicrobial resistance surveillance and strengthened in-hospital infection control are essential to guide appropriate antibiotic use and to curb the spread of resistant organisms.

The emergence of metallo-beta-lactamase gene variants, such as blaIMP-26, has posed a significant challenge to bacterial infection treatment, drawing considerable attention in public health. This study aims to investigate the resistance mechanism of blaIMP-26-carrying clinical Enterobacter xiangfangensis in China. blaIMP-26-harboring carbapenem-resistant Enterobacteriaceae (CRE) isolates were collected from a multicenter study across China. The blaIMP-26 was identified by polymerase chain reaction (PCR). Multi-locus sequence typing (MLST) and phylogenetic analysis were conducted to investigate the genetic evolutionary characterization of Enterobacteriaceae carrying blaIMP-26. The genomic contexts of these strains were explored by whole genome sequencing, while conjugation and plasmid stability assays were conducted to assess the transferability and maintenance of the resistance plasmids. Furthermore, the antibiotic susceptibility of IMP-26 to β-lactams was evaluated through antimicrobial susceptibility testing, enzyme kinetic analysis, and molecular docking. Five blaIMP-26-carrying strains were collected, and all were multidrug-resistant Enterobacter xiangfangensis. blaIMP-26 was located either on IncHI2/2A or the novel IncpKPC-CAV1321 plasmid, both exhibiting high and stable self-transfer frequency. In addition, blaIMP-26 was identified within a novel class 1 integron In437, or the classical integron In837. Antimicrobial susceptibility testing and enzyme kinetic assay further showed that IMP-26 could mediate high levels of resistance to common carbapenem and cephalosporin antibiotics. This study characterized the genomic and clinical characteristics of blaIMP-26-carrying clinical Enterobacter xiangfangensis in China. The high carbapenem resistance and transmission capacity of blaIMP-26 highlight the need for enhanced surveillance and preventive measures to contain the spread of blaIMP-26.IMPORTANCEOur research has led to the documentation of a novel IncpKPC-CAV1321 plasmid and the discovery of a novel integron In437, both carrying the blaIMP-26 gene. A comprehensive analysis of the carbapenem resistance levels and enzymatic kinetics exhibited by IMP-26 revealed that IMP-26 could mediate high levels of resistance to common carbapenem and cephalosporin antibiotics. Our findings underscore the critical need for enhanced surveillance and preventive measures to curtail the dissemination of blaIMP-26.

The emergence of ceftazidime-avibactam resistance in Klebsiella pneumoniae poses a significant public health threat, driven by mutations in the bla . This study investigates the evolution of KPC variants (KPC-33, KPC-84, KPC-190) during therapy, highlighting their impact on resistance profiles and treatment challenges. Understanding these mechanisms is critical for guiding clinical interventions. Four K. pneumoniae strains were isolated from a patient undergoing ceftazidime-avibactam therapy. Antimicrobial susceptibility testing and bioinformatics tools were used to characterize genetic mutations and their phenotypic effects. Whole genome sequencing, cloning, and enzymatic kinetic assays were performed to analyze resistance mechanisms. The study identified mutations in the Ω-loop and 240-loop of KPC-2, leading to reduced avibactam affinity and increased ceftazidime hydrolysis. KPC-33 restored carbapenem susceptibility, while KPC-84 and KPC-190 conferred dual resistance. Enzymatic assays confirmed altered kinetic parameters, correlating with clinical resistance patterns. KPC variants exhibit complex evolutionary pathways under antibiotic pressure, complicating treatment. Enhanced surveillance and optimized dosing regimens, including higher avibactam concentrations, are recommended to mitigate resistance. This study underscores the need for global monitoring of KPC variants to inform therapeutic strategies.

Introduction: With the large-scale use of antibiotics, the detection rate and mortality of carbapenem resistant Escherichia coli (CR-EC) have gradually increased. This study investigated the molecular characteristics and prevalence of CR-EC in order to supplement the isolated data of CR-EC in Hangzhou, China. Methodology: The minimal inhibitory concentration was determined by microbroth dilution method. The drug resistance genes were detected by polymerase chain reaction. The transferability of plasmid was verified by the conjugation test and genetic homology was detected by pulsed-field gel electrophoresis. The whole genome was sequenced (WGS) using the Illumina MiSeq technology. Results: A total of 8 non-duplicated CR-EC isolates were collected, and all exhibited a multidrug-resistant phenotype. Two different New Delhi metallo-β-lactamase (NDM) variants, blaNDM-5 and blaNDM-13, were found with detection rates of 62.5% and 12.5%, respectively. The success rate of conjugation was 100% (6/6). Homology analysis showed that there was no widespread cloning outbreak of CR-EC, and blaNDM-5-ST410 was prevalent in the local area as a dominant group. WGS also indicated the rate of occurrence of resistance genes carrying resistance for more types of antibiotics, as well as exposed potential virulence risks. Conclusions: This was a survey on the prevalence and molecular characteristics of CR-EC in Hangzhou. blaNDM-like production combined with extended spectrum beta-lactamase (ESBLs) and/or AmpC was the main resistance mechanism of CR-EC in this area. The dominant blaNDM-5-ST410 requires enhanced attention. The horizontal transformation of plasmids, complex drug resistance, and potential virulence risks also need close attention.

Objective:To analyze the changes in the distribution and drug resistance of pathogenic bacteria causing urinary tract infections in Southwest China from 2019 to 2023, and to provide an accurate scientific basis for empirical clinical use. Methods:The identification results and drug susceptibility tests of non-duplicate pathogens isolated from urine samples of patients in Sichuan region from 2019 to 2023 were retrospectively analyzed. The results obtained were interpreted with reference to CLSI M100-33th and analyzed with WHONET 5.6 software. Results:A total of 247295 strains of pathogens were detected, including 188551 gram-negative strains (76.2%). The positive rate of female patients (56.8%) was significantly higher than that of male patients (43.2%). The top five most common urinary pathogens were Escherichia coli (50.5%), Enterococcus faecium (11.5%), Klebsiella pneumoniae (8.5%), Enterococcus faecalis (6.5%), and Proteus mirabilis (2.9%). The resistance rate of E.coli to levofloxacin, cefotaxime and ceftriaxone was higher (>50%) and had a certain upward trend. The resistance rates of Klebsiella pneumoniae to imipenem and meropenem increased from 7.8% and 9.6% in 2019 to 11.6% and 13.2% in 2023, respectively, much higher than the resistance rates of E. coli to carbapenem antibiotics (<2%). E. coli, K. pneumoniae and E. cloacae still maintained high activity against tigecycline and polymyxin B. The drug resistance rate of Acinetobacter baumannii to imipenem and meropenem was more than 27.4%. The resistance rates of Enterococcus faecium and Enterococcus faecalis to vancomycin, teicoplanin and linezolid were lower than 3.4%. There was an increasing trend in the detection of CRE-KPN among multidrug-resistant bacteria, and a slight decreasing trend in CRPA and CRAB. Conclusion:The main pathogens of urinary tract infections were E. coli, E. faecium and K. pneumoniae. The drug resistance rates of main clinically isolated bacteria in urine samples showed a diverse trend. Antibiotics should be rationally selected based on the resistance patterns of the pathogens. At the same time, with the continuous detection of multi-drug resistant bacteria VRE and CRE, we have a long way to go in future drug resistance monitoring.

Stenotrophomonas maltophilia is a multidrug-resistant pathogen, which poses a major challenge to clinical management due to its increasing resistance to common antibiotics, such as levofloxacin (LEV) and trimethoprim-sulfamethoxazole (SXT), and poor clinical response to treatment. There is an urgent need for rapid and reliable antimicrobial susceptibility testing (AST) methods to improve treatment outcomes. This study collected 441 S. maltophilia strains, performed whole-genome sequencing, and used machine learning to identify key resistance determinants for LEV and SXT, constructing predictive models for resistance phenotypes. The 441 S. maltophilia strains we collected show significant genomic diversity and representative lineage distribution. Machine learning identified key resistance markers for LEV and SXT, improving area under the curve values to 92.80% for LEV and 95.44% for SXT. Validation accuracies reached 94.87% for LEV and 96.27% for SXT. Mutations in parC, smeT, and gyrA were strongly associated with LEV resistance. The gene presence of sul1, sul2, and CEQ03_18740, as well as gene mutations in Gsh2, prmA, and gspD, were highly correlated with SXT resistance. These findings suggest that integrating genome-based markers can enhance the prediction of antimicrobial resistance, offering a robust method for clinical application. Genotypic AST can reliably predict resistance phenotypes, providing a promising alternative to traditional AST methods for S. maltophilia infections. IMPORTANCE:Stenotrophomonas maltophilia is an emerging multidrug-resistant pathogen, making treatment challenging and requiring more effective diagnostic methods. This study offers a novel approach by integrating whole-genome sequencing with machine learning to identify key resistance markers for levofloxacin and trimethoprim-sulfamethoxazole. The predictive models developed can reliably forecast antimicrobial resistance phenotypes, providing a faster and more accurate alternative to traditional susceptibility testing. This approach not only enhances clinical decision-making but also aids in the timely administration of appropriate therapies. By identifying specific genomic markers associated with resistance, this study lays the foundation for future development of personalized treatment strategies, addressing the growing concern of antibiotic resistance.

Mucormycosis is a lethal fungal infection disease with high mortality rate. However, investigations assessing the value of metagenomic next-generation sequencing (mNGS) for distinguishing Mucorales infection from colonization are currently insufficient. A retrospective analysis of clinical date from 71 patients at Sichuan Provincial People’s Hospital from September 2021 to September 2024 was conducted. The performance of mNGS in distinguishing Mucorales infection from colonization, along with the differences in patients’ characteristics, imaging characteristics, antimicrobial adjustment, and microbiota, were examined. Among the 71 patients, 51 were identified as Mucorales infection group (3 proven and 48 probable cases), and 20 were colonization group (possible cases). Receiver operating characteristic (ROC) curve for mNGS indicated an area under the curve of 0.7662 (95%CI: 0.6564-0.8759), with an optimal threshold value of 51 for discriminating Mucorales infection from colonization. The infection group exhibited a higher proportion of antimicrobial adjustments compared to the colonization group (64.71% vs. 35.00%, P < 0.05), with antifungal agent changed being more dominant (43.14% vs. 10.00%, P < 0.01). Mucorales RPTM value, length of hospital stays, hsCRP, immunocompromised, malignant blood tumor, and antifungal changed were significantly positively correlated with Mucorales infection. Rhizomucor pusillus showed significant differences between the two groups. The abundance of Torque teno virus significantly increased in the infection group, whereas the colonization group exhibited higher abundance of Rhizomucor delemar. mNGS is a valuable tool for differentiating colonization from infection of Mucorales. Malignant blood tumor, immunocompromised, length of hospital stays and hsCRP were significant different indicators between patients with Mucorales infection from colonization.

Objective:The purpose of this study was to assess the frequency distribution of bacterial pathogens causing bloodstream infections (BSIs) as well as the characteristics of antibiotic susceptibility and resistance to gain a deeper understanding of the drug resistance situation in the southwest China. Methods:Non-duplicate pathogenic bacteria according to the American Clinical and Laboratory Standards Institute (CLSI) M100 and analyzed using WHONET 5.6 software. Results:A total of 170,246 non-duplicated pathogenic bacteria were isolated from blood from 2016 to 2023. Gram-negative bacteria accounted for 59.5% and Gram-positive bacteria accounted for 40.5%. The top five detection rates were Escherichia coli (33.9%), coagulase-negative staphylococci (21.7%), Klebsiella pneumoniae (11.5%), Staphylococcus aureus (7.0%), and Enterococcus spp (5.4%). Streptococcus pneumoniae, Salmonella spp and β-Hemolytic Streptococcus were significantly more frequently isolated in pediatric patients than in adult patients. The rate of resistance to carbapenems was less than 1.2% in the Escherichia coli over the 8-year period, with a significant upward trend in the Klebsiella pneumoniae. The overall resistance rate of Pseudomonas aeruginosa to imipenem and meropenem had a slow decreasing trend. The resistance rate of Acinetobacter baumannii to imipenem and meropenem has been maintained at a high level, which is greater than 50%. The detection rate of MRSA was 27.70% and vancomycin- and linezolid-resistant strains were not found. The resistance rates of Enterococcus faecium and Enterococcus faecalis to vancomycin, linezolid and teicoplanin were less than 2.1%. Conclusion:The pathogenic bacteria of bloodstream infection in southwest China were diversified, and the multi-drug resistant bacteria, especially Carbapenem-resistant Klebsiella pneumoniae (CRKP), had increased significantly, posing a serious challenge to clinical treatment. Additionally, the situation of Methicillin-resistant Staphylococcus aureus (MRSA) and Vancomycin-resistant Enterococcus (VRE) also required close attention.

Background: Surveillance systems revealed that the prevalence of vancomycin-resistant Enterococcus faecium (VREfm) has increased. We aim to investigate the epidemiological and genomic characteristics of VREfm in China. Methods: We collected 20,747 non-redundant E. faecium isolates from inpatients across 19 hospitals in six provinces between January 2018 and June 2023. VREfm was confirmed by antimicrobial susceptibility testing. The prevalence was analyzed using changepoint package in R. Genomic characteristics were explored by whole-genome sequencing. Results: 5.59% (1159/20,747) of E. faecium isolates were resistant to vancomycin. The prevalence of VREfm increased in Guangdong province from 5% before 2021 to 20-50% in 2023 (p < 0.0001), but not in the other five provinces. Two predominant clones before 2021, ST17 and ST78, were substituted by an emerging clone, ST80, from 2021 to 2023 (88.63%, 195/220). All ST80 VREfm from Guangdong formed a single lineage (SC11) and were genetically distant from the ST80 VREfm from other countries, suggesting a regional outbreak. All ST80 VREfm in SC11 carried a new type of plasmid harbouring a vanA cassette, which was embedded in a Tn1546-like structure flanked by IS1678 and ISL3. However, no conjugation-related gene was detected and no transconjugant was obtained in conjugation experiment, indicating that the outbreak of ST80 VREfm could be attributed to clonal transmission. Conclusions: We revealed an ongoing outbreak of ST80 VREfm with a new vanA-harbouring plasmid in Guangdong, China. This clone has also been identified in other provinces and countries, foreboding a risk of wider spreading shortly. Continuous surveillance is needed to inform public health interventions.

Idiopathic pulmonary fibrosis (IPF) is a chronic and lethal lung disease characterized by progressive lung scarring. This study aims to elucidate the role of the E3 ubiquitin ligase NEDD4 in the ubiquitination of YY1 and its subsequent impact on TAB1 transcription, revealing a possible molecular mechanism in the development of IPF. Through bioinformatics analysis and both in vitro and in vivo experiments, we observed differential expression levels of NEDD4 and YY1 between normal and IPF samples, identifying NEDD4 as an upstream E3 ubiquitin ligase of YY1. Furthermore, binding sites for the transcription factor YY1 on the promoter region of TAB1 were discovered, indicating a direct interaction. In vitro experiments using HEPF cells showed that NEDD4 mediates the ubiquitination and degradation of YY1, leading to suppressed TAB1 transcription, thereby inhibiting cell proliferation and fibrogenesis. These findings were corroborated by in vivo experiments in an IPF mouse model, where the ubiquitination pathway facilitated by NEDD4 attenuated IPF progression through the downregulation of YY1 and TAB1 transcription. These results suggest that NEDD4 plays a crucial role in the development of IPF by modulating YY1 ubiquitination and TAB1 transcription, providing new insights into potential therapeutic targets for treating IPF.

Introduction: Enterobacter chengduensis was defined as a novel species in the genus. Enterobacter in 2019, however, antimicrobial resistance, such as carbapenem resistance, has rarely been described in E. chengduensis. This study described the molecular features of four carbapenem-resistant E. chengduensis strains collected from a tertiary health care hospital in Southwest China. Methods: Whole genome sequencing (WGS) was used to determine the genome sequence of four E. chengduensis strains. The precise species of strains were identified by average nucleotide identity (ANI) and in silico DNA-DNA hybridization (isDDH). The clonal relatedness of four E. chengduensis strains and additional 15 ones from NCBI were examined through phylogenetic analysis. The molecular features of E. chengduensis and genetic structure of carbapenemase- encoding plasmids were characterized through genomic annotation and analysis. Results: The results revealed the emergence of bla(NDM-1)-carrying E. chengduensis strains in China. Multilocus sequence typing (MLST) analysis showed that all 19 E. chengduensis belonged to the same sequence type of ST414. Core SNP analysis suggested the potential intrahospital clonal transmission of ST414 E. chengduensis. The carbapenemase-encoding gene bla(NDM-1) was harbored by an IncC-type plasmid, which was experimentally confirmed to be able to conjugate. Discussion This study reports the first emergence and potential clonal transmission of bla(NDM-1)-carrying E. chengduensis. Further surveillance should be advocated to monitor the dissemination of carbapenem-resistant E. chengduensis and bla(NDM-1)-harboring IncC-type plasmids in China.

Purpose: We analyzed the pathogenic bacteria and antibiotic resistance distributions in patients with biliary tract infections (BTI) using samples from the Antimicrobial Resistant Investigation Network of Sichuan Province (ARINSP) to promote the rational use of antibiotics to reduce multidrug resistance. Patients and Methods: Participating hospitals identified isolates between 2017 and 2023 and conducted antimicrobial susceptibility tests. Isolated bacteria were identified and tested for drug sensitivity using MOLDI-TOF mass spectrometry system, VITEK automated drug sensitivity system and paper diffusion method, and the results were interpreted with reference to CLSI M100 30th edition standards. WHONET 5.6 was used to analyze the results. Results: In total, 25,573 bacterial isolates were collected; 18,134 were Gram-negative (70.9%). The top five most frequently isolated bacteria were Escherichia coli (8,181/25,573; 32.0%), Klebsiella pneumoniae (3,247/25,573; 12.7%), Enterococcus faecium (2,331/ 25,573; 9.1%), Enterococcus faecalis (1,714/25,573; 6.7%), and Enterobacter cloacae (1,429/25,573; 5.6%). E. coli and E. faecalis slowly declined over time, while K. pneumoniae slowly increased; E. faecium frequency was stable; E. coli resistance to ampicillin was the highest among all antibiotics tested; resistance rates decreased with the addition of sulbactam. K. pneumoniae resistance to aztreonam, imipenem, meropenem, ertapenem, and chloramphenicol remained low. E. cloacae was highly resistant to cephalosporins, especially cefoxitin and cefazolin. E. faecalis' resistance to teicoplanin remained low, decreasing from 6.9% in 2017 to 0.0% in 2019 before stabilizing. Conclusion: The most frequently isolated bacteria from patients with BTIs were Enterobacteriaceae, including E. coli and K. pneumoniae, followed by E. faecium and E. faecalis. Isolates exhibited high resistance to routinely used antibiotics (cephalosporins) and were highly sensitive to tigecycline, carbapenem, amikacin, and vancomycin. The results guide the rational use and continual revision of antibiotic regimens for BTIs to reduce antibiotic resistance.

Aims Adequately and accurately identifying carbapenemase-producing Enterobacterales (CPE) is vital for selecting appropriate antimicrobial therapy and implementing effective infection control measures. This study aims to optimize the phenotypic detection method of carbapenemase for routine diagnostics in clinical microbiology laboratories.Methods and Results Carbapenemase genes in 2665 non-duplicate CRE clinical strains collected from various regions of China were confirmed through whole-genome sequencing (WGS). The carbapenemase inhibition test (CIT) was conducted and interpreted using different methods and breakpoints, then compared with the NG-Test CARBA 5 for carbapenemase detection. The diagnostic performance of the CIT method was optimal when the carbapenemase types were determined by comparing the inhibition zone diameters of the imipenem disc with 3-aminophenylboronic acid (APB) plus ethylenediaminetetraacetic acid (EDTA) to those of the imipenem disc with either APB or EDTA alone, with a breakpoint of 4 mm. The overall sensitivities of the current CIT, the modified CIT, and NG-Test CARBA 5 were 91.4%, 94.9%, and 99.9%, respectively. For detecting isolates co-producing Klebsiella pneumoniae carbapenemase (KPC) and metallo-beta-lactamases (MBLs), the modified CIT method had higher sensitivity than the current method (70.0% vs. 53.3%), though this difference was not statistically significant (P = 0.063). The NG-Test CARBA 5 showed excellent performance for multi-carbapenemases diagnosis, with sensitivity and specificity of 97.1% and 100%, respectively.Conclusions Optimizing and standardizing the CIT method for clinical use is necessary. It has certain advantages in diagnosing multi-carbapenemase and rare carbapenemase production. However, for identifying common carbapenemase types, the NG-Test CARBA 5 demonstrated superior performance.

Carbapenem-resistant (CR) Klebsiella oxytoca complex can be associated with high mortality, emerging as a new threat to the public health. K. oxytoca complex is phylogenetically close to K. pneumoniae, one of most common species associated with multidrug resistance in Enterobacterale. The latest research showed that K. oxytoca is a complex of six species. Currently, the epidemiological and genomic characteristics of CR K. oxytoca complex in China are still unclear. Here, we conducted a multi-center study on 25 CR K. oxytoca complex collected from five representative regions in China. These isolates were, respectively, recovered from respiratory tract (12 cases, 48.0%), abdominal cavity (5 cases, 20.0%), blood (4 cases, 16.0%), urine tract (3 cases, 12.0%) and skin or soft tissue (1 cases, 4.0%). Among them, 32.0% (8/25) of patients infected with K. oxytoca complex had a poor prognosis. In this study, three K. oxytoca complex species were detected, namely K. michiganensis, K. oxytoca and K. pasteurii, among which K. michiganensis was the most common. Three carbapenemase genes were identified, including blaNDM-1 (10, 38.5%), blaKPC-2 (9, 34.6%) and blaIMP (6 blaIMP-4 and 1 blaIMP-8; 7, 26.9%). Subsequent multilocus sequence typing identified various sequence types (STs), among which ST43, ST92 and ST145 were relatively common. Different from the clonal dissemination of high-risk carbapenem-resistant K. pneumoniae strains, our research revealed a polyclonal dissemination characteristic of CR K. oxytoca complex in China. S1-nuclease PFGE and Southern blot experiment showed that carbapenemase genes were encoded in plasmids of different sizes. Two blaNDM-harboring plasmids were subsequently sequenced, and were characterized to be IncX3 and IncC incompatibility groups, respectively. This is the first multi-center study of CR K. oxytoca complex in China, which improved our understanding of the prevalence and antimicrobial resistance characteristics of CR K. oxytoca complex in China.

ABSTRACT Carbapenem-resistant and hypervirulent Klebsiella pneumoniae (CR-hvKP) strains are increasingly reported, posing a significant threat to public health. Therefore, effective antimicrobial therapy is urgently needed. This study aimed to analyze the in vitro activity of ceftazidime-avibactam (CZA), imipenem-relebactam (IMR), and aztreonam-avibactam (AZA) toward CR-hvKP and carbapenem-resistant Klebsiella pneumoniae (CRKP) isolates. Non-repetitive clinical CRKP and CR-hvKP strains were collected from Sichuan Provincial People’s Hospital between August 2018 and June 2022. CR-hvKP strains were screened using string tests and polymerase chain reaction (PCR). The microbroth dilution method was used to evaluate in vitro antibacterial activity of CZA, IMR, and AZA toward CRKP and CR-hvKP stains. The molecular characteristics of CRKP and CR-hvKP strains were investigated using PCR amplification. The virulence features of CR-hvKP strains were investigated using serum resistance assays and a Galleria mellonella infection model. A total of 114 CRKP and 40 CR-hvKP strains were collected. The susceptibility rates of CRKP and CR-hvKP to tigecycline, colistin, and polymyxin B exceeded 89.5%. The susceptibility rates of CRKP and CR-hvKP to CZA were 64.0% and 77.5%, respectively; the susceptibility rates to IMR were 92.5% and 71.9%, respectively; and the susceptibility rates to AZA were 89.5% and 75.0%, respectively. Multilocus sequence typing and wzi-loci sequencing identified sequence type 11 KL64 as the predominant type in CRKP and CR-hvKP strains. Carbapenemase genes were dominated by blaKPC-2 and blaNDM-1. IMR and AZA may be promising therapeutic agents for the treatment of infections caused by CRKP and CR-hvKP isolates. IMPORTANCE To our knowledge, this is the first study to report the in vitro activity of two novel antimicrobial drugs, including imipenem-relebactam (IMR) and aztreonam-avibactam (AZA), toward carbapenem-resistant and hypervirulent Klebsiella pneumoniae (CR-hvKP) strains. Our in vitro activity study revealed that only few antibacterial agents (including several novel agents) exhibit high antimicrobial activity toward carbapenem-resistant Klebsiella pneumoniae (CRKP) and CR-hvKP isolates. IMR and AZA may be promising therapeutic agents for the treatment of infections caused by CRKP and CR-hvKP isolates.

ABSTRACT The infection proportion of Candida orthopsilosis , a member of the C. parapsilosis complex, has increased globally in recent years, and nosocomial outbreaks have been reported in several countries. This study aimed to establish microsatellite loci-based typing method that was able to effectively distinguish among C. orthopsilosis isolates. Three reference C. orthopsilosis genome sequences were analyzed to identify repeat loci. DNA sequences containing over eight bi- or more nucleotide repeats were selected. A total of 51 loci were initially identified, and locus-specific primers were designed and tested with 20 epidemiologically unrelated isolates. Four loci with excellent reproducibility, specificity, and resolution for molecular typing purposes were identified, and the combined discriminatory power (DP, based on 20 epidemiologically unrelated isolates) of these four loci was 1.0. Reproducibility was demonstrated by consistently testing three strains each in triplicate, and stability, demonstrated by testing 10 successive passages. Then, we collected 48 C . orthopsilosis non-duplicate clinical isolates from the China Hospital Invasive Fungal Surveillance Net study to compare the DP of the microsatellite-based typing with internal transcribed spacer (ITS) and amplified fragment length polymorphism (AFLP) typing analyses, using ATCC 96139 as a reference strain. These 49 isolates were subdivided into 12 microsatellite types (COMT1–12), six AFLP types, and three ITS types, while all the isolates with the same COMT belonged to consistent AFLP and ITS type, demonstrating the high DP of our microsatellite-type method. According to our results, COMT12 was found to be the predominant type in China, and COMT5 was the second largest and responsible for causing a nosocomial outbreak. This microsatellite-type method is a valuable tool for the differentiation of C. orthopsilosis and could be vital for epidemiological studies to determine strain relatedness and monitor transmission.