Search

PurposeCarbapenem-resistant Klebsiella pneumoniae (CRKP) producing carbapenemases poses a global threat to public health. Antimicrobial agent combinations have been promoted as a potential therapeutic strategy for infections. The most effective antimicrobial combinations against CRKP strains producing different carbapenemases are currently unclear, particularly those producing the KPC variant carbapenemases. This study is aimed to evaluate the effectiveness of various antimicrobial agent combinations against CRKP strains with different carbapenemases.MethodsA checkerboard assay involving 24 antimicrobial agent combinations was conducted on 44 strains of carbapenemase-producing CRKP isolated from patients of which 13 CRKP strains carried single KPC variants. The 24 antimicrobial combinations were based on meropenem, polymyxin, tigecycline, ceftazidime/avibactam, respectively. The fractional inhibitory concentration (FIC) indexes were calculated for each combination of antimicrobial agents.ResultsThe distribution of carbapenemases in 44 CRKP strains was as follows: KPC variants (n = 13, 29.5%), KPC-2 (n = 10, 22.7%), metallo-β-lactamases (n = 9, 20.5%), OXA-48-like (n = 12, 27.3%). In the checkerboard assay, the combination of polymyxin and aztreonam exhibited the highest synergistic effect against CRKP strains, with a rate of 95.5% (42/44). This was followed by polymyxin-meropenem at 88.6% (39/44) and polymyxin-levofloxacin at 68.2% (30/44). Additionally, polymyxin-aztreonam combination and polymyxin-meropenem showed the highest sum of synergistic and additive rates of 100.0% against KPC variant-producing CRKP strains. Notably, ceftazidime/avibactam-based combinations exhibited better synergistic effects on KPC variant-producing CRKP strains compared to other CRKP strains with adjusted p value

Edwardsiella tarda is frequently isolated from aquatic animals and environments. While human infections caused by E. tarda are rare, some extraintestinal infections can be severe. This case report describes a patient with cellulitis of the right upper extremity of unknown origin. Metagenomic next-generation sequencing (mNGS) indicated that the patient was infected with E. tarda. Antimicrobial susceptibility testing revealed that the isolate was resistant to quinolones and trimethoprim/sulfamethoxazole. The isolate, positive for four virulence genes (fimA, gadB, mukF, and sodB), was confirmed to be virulent using the Galleria mellonella larvae model. Following early pus drainage and a 9-day course of imipenem, the patient ultimately recovered. This case report aimed to illustrate the presentation, diagnosis, and management of uncommon cellulitis caused by drug-resistant, virulent E. tarda.

The acquisition of resistance to one antibiotic sometimes leads to collateral sensitivity to a second antibiotic. Here, the authors show that vancomycin resistance in Enterococcus faecium is associated with a remarkable increase in susceptibility to pleuromutilin antibiotics, such as lefamulin.

Summary Colistin is recognized as a last‐resort treatment option against multi‐drug resistant bacteria including carbapenem‐resistant Enterobacteriaceae (CRE). However, the plasmid‐mediated colistin‐resistance gene mcr‐1 has been reported globally resulting in an increase of colistin‐resistant bacteria. A quick and accurate method for determining the pathogen resistance of colistin is therefore crucial in the clinic. Matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS) is a potential tool forto be applied for antimicrobial susceptibility testing. We compared the growth of Escherichia coli strains in the presence or absence of colistin. Automated analyses of the spectra were performed with a prototype software tool written with package R. Three mcr‐1‐positive and six mcr‐1‐negative E. coli were used for establishing the model to obtain the optimal incubation time, the breakpoint concentration of colistin and cut‐off of the relative growth (RG) value. The distinction between susceptible and resistant strains was already noticeable after 2 h of incubation. The best separation between the susceptible and resistant strains was achieved at a concentration of 4 µg ml‐1 and a relative growth cut‐off value of 0.6. Application of the model for the analysis of 128 E. coli isolates, a sensitivity of 97.4% and a specificity of 88.2% were achieved compared with colistin MIC results. The rapid MALDI‐TOF MS‐based method approach is simple to set‐up, uses a short incubation time, and had excellent outcomes with respect to sensitivity and specificity for colistin sensitivity testing in Escherichia coli.

Carbapenem-resistant and hypervirulent Klebsiella pneumoniae strains are emerging. Here Xie et al. show that these phenotypes are carried on a plasmid formed from the fusion of a virulence plasmid with a conjugative plasmid.

A rectal swab sample was collected from a patient with Guillain–Barré syndrome and enriched in lysogeny broth. Carbapenem-resistant bacteria were selected by China Blue agar plates containing 0.3 μg/ml meropenem. Carbapenemase-producing Klebsiella michiganensis was identified and characterized by matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF), immune colloidal gold technique, a conjugation experiment, PCR analysis, and antimicrobial susceptibility testing. The genome of K. michiganensis was determined by whole genome sequencing. Antimicrobial susceptibility testing showed that the K. michiganensis was resistant to imipenem, meropenem, ertapenem, cefmetazole, ceftazidime, cefotaxime, piperacillin/tazobactam, sulbactam/cefoperazone, ceftazidime/avibactam, cefepime, and aztreonam while susceptible to polymyxin B, ciprofloxacin, tigecycline, and amikacin. Immune colloidal gold technique suggested that this strain co-produced three different carbapenemases [Klebsiella pneumoniae carbapenemase (KPC), New Delhi metallo-beta-lactamase (NDM), and Imipenem (IMP)]. Whole genome sequencing analysis indicated that this strain belonged to ST91, and blaKPC–2, blaNDM–1, and blaIMP–4 were carried on different conjugative plasmids. Besides, the co-existence and transferability of blaKPC–2, blaNDM–1, and blaIMP–4 in K. michiganensis facilitates the potential horizontal dissemination and nosocomial spread of resistance genes among multidrug-resistant organisms.

Carbapenem-resistant Enterobacterales (CRE) are increasingly recognized as an urgent public health concern. The rapid and accurate identification of carbapenemases could provide insights into antimicrobial therapy and infection control. In this study, we evaluated the efficacy of three different methods, including the NG-test Carba 5, colloidal gold immunoassay (CGI) test, and Xpert Carba-R assay, for the rapid detection of five carbapenemases (KPC, NDM, IMP, OXA-48, and VIM). A total of 207 Gram-negative strains collected from patients and hospital sewages were tested. The presence or absence of carbapenemase genes in the whole-genome sequences was used as the gold standard for evaluating the accuracy of the above-mentioned three methods. Among the 192 strains carrying only one carbapenemase gene, the accuracies of the NG-Test Carba 5, CGI test, and Xpert Carba-R were 96.88% (95% CI, 93.01–98.72%), 96.88% (95% CI, 93.01–98.72%), and 97.92% (95% CI, 94.41–99.33%), respectively. Xpert Carba-R was able to detect all 13 types of KPC variants, including KPC-2, KPC-3, KPC-25, KPC-33, KPC-35, KPC-51, KPC-52, KPC-71, KPC-76, KPC-77, KPC-78, KPC-93, and KPC-123, with a detection sensitivity of 100.00% (95% CI, 96.50–100.00%), a specificity of 100.00% (95% CI, 92.38–100.00%), and a κ index of 1.00. For IMP, Carba 5 was superior to the other two methods, with a sensitivity of 100% (95% CI, 71.66–100.00%), a specificity of 100% (95% CI, 97.38–100.00%), and a κ index of 1.00. For the remaining 15 strains carrying two or three kinds of carbapenemase genes, Carba 5 performed the best, which accurately identified all the target genes, followed by Xpert Carba-R (12/15, 80.00%) and the CGI test (10/15, 66.67%). Therefore, all three assays demonstrated reliable performances in carbapenemase detection, and Xpert Carba-R should be recommended for the detection of KPC variants, especially for patients at a high risk of infections caused by ceftazidime/avibactam-resistant strains. IMPORTANCE: CRE was listed as one of the top three pathogens that are in critical need of new antibiotics by the WHO. The rapid and accurate identification of carbapenemases is important for antimicrobial therapy and infection control. In recent years, new beta-lactam/beta-lactamase inhibitor combinations such as ceftazidime/avibactam (CZA) have been approved by the Food and Drug Administration (FDA) to cope with CRE challenges. CZA was effective against class A, class C, and some class D enzymes such as OXA-48-like. However, CZA-resistant KPC variants emerged at an alarming speed, which posed a new challenge for the accurate identification of KPC variants. In this study, we evaluated the performance of two lateral flow immunochromatographic assays, namely, NG-test Carba 5 and the CGI test, and the automated real-time quantitative PCR Xpert Carba-R in the rapid detection of carbapenemases. Notably, 13 types of KPC variants were enrolled in this study, which covered most KPC variants discovered in China. Carba-R was superior to NG-teat Carba 5 and the CGI test; it was able to detect all of the included KPC variants, including KPC-2, KPC-3, KPC-25, KPC-33, KPC-35, KPC-51, KPC-52, KPC-71, KPC-76, KPC-77, KPC-78, KPC-93, and KPC-123.

Gastrointestinal carriage is regarded as a major reservoir of K. pneumoniae infections, especially in intensive care patients. A total of 101 (95.3%) KPC-producing carbapenem-resistant K. pneumoniae (CRKP) isolates were identified among 106 CRKP isolates collected from stool samples of inpatients performing active rectal screening for carbapenem-resistant Enterobacteriaceae during hospitalization in the ICUs of a tertiary hospital between 2016 and 2017. Among them, six KPC-producing CRKP isolates from three patients (two isolates for each patient) were identified with distinct antibacterial susceptibility. Our findings showed that: (1) blaKPC–2 gene is predominant in CRKP strains isolated from the intensive care patients and can be incorporated into various plasmids that are transmissible among multiple bacterial hosts in the human gastrointestinal tract; (2) the human gastrointestinal tract has a capacity to dynamically colonize multiple clones of CRKP strains with varied plasmids, diverse antimicrobial resistance genes and virulence genes. K. pneumoniae colonization is an important step in progression to extraintestinal infection, which provides the rationale for establishing intervention measures to prevent subsequent infection. Thus, close surveillance on CRKP colonization, together with effective infection prevention and control measures, should be put into practice.

Objective Incomplete thermal ablation (ITA) fosters the malignancy of residual cells in Hepatocellular carcinoma (HCC) with unclear mechanisms now. This study aims to investigate the expression changes of NDST2 following ITA of HCC and its impact on residual cancer cells.Methods An in vitro model of heat stress-induced liver cancer was constructed to measure the expression of NDST2 using Quantitative Real-Time PCR and Western blotting experiments. The sequencing data from nude mice were used for validation. The clinical significance of NDST2 in HCC was evaluated by integrating datasets. Gene ontology and pathway analysis were conducted to explore the potential signaling pathways regulated by NDST2. Additionally, NDST2 was knocked down in heat stress-induced HCC cells, and the effects of NDST2 on these cells were verified using Cell Counting Kit-8 assays, scratch assays, and Transwell assays.Results NDST2 expression levels are elevated in HCC, leading to a decrease in overall survival rates of HCC patients. Upregulation of immune checkpoint levels in high NDST2-expressing HCC may contribute to immune evasion by liver cancer cells. Additionally, the low mutation rate of NDST2 in HCC suggests a relatively stable expression of NDST2 in this disease. Importantly, animal and cell models treated with ITA demonstrate upregulated expression of NDST2. Knockdown of NDST2 in heat stress-induced liver cancer cells results in growth inhibition associated with gene downregulation.Conclusion The upregulation of NDST2 can accelerate the progression of residual HCC after ITA, suggesting a potential role for NDST2 in the therapeutic efficacy and prognosis of residual HCC.

A heterogeneous nanocomposite (NC) of g-C3N4/W18O49 based on the coupling of W18O49 nanorods (NRs) with the graphitic carbon nitride (g-C3N4) sheets has been synthesised via a solvothermal method. The as-synthesised products were characterised by X-ray diffraction, X-ray photoelectron spectrometry, and transmission electron microscopy. The g-C3N4/W18O49 NC exhibited very strong adsorption ability towards the methylene blue (MB) dye and demonstrated a high removal efficiency of 99.14% after 0.5 h equilibration in dark. Compared to the g-C3N4 sheets andW18O49 NRs, the g-C3N4/W18O49 NC exhibited higher removal efficiencies towards both the MB and methyl orange (MO) dyes via a combination of adsorption and degradation. The photocatalytic process of the g-C3N4/W18O49 NC followed the Z-scheme photocatalytic mechanism. This work provides an efficient strategy for the synthesis of g-C3N4-based heterogeneous photocatalysts. [ABSTRACT FROM AUTHOR]

Hypertriglyceridemia is an important contributor to atherosclerotic cardiovascular disease (ASCVD) and acute pancreatitis. Familial hypertriglyceridemia is often caused by mutations in genes involved in triglyceride metabolism. Here, we investigated the disease-causing gene mutations in a Chinese family with hypertriglyceridemia and assessed the functional significance in vitro. Whole-exome sequencing (WES) was performed revealing that the severe hypertriglyceridemic proband carried a missense mutation (c.590G > A) in exon 5 of the LPL gene, as well as a missense mutation (c.1523C > T) in exon 10 of the LMF1 gene. Conservation analysis by Polyphen-2 showed that the 508 locus in the LMF1 protein and 197 locus in the LPL protein were highly conserved between different species. I-TASSER analysis indicated that the LMF1 c.1523C > T mutation and the LPL c.590G > A mutation changed the tertiary structure of the protein. A decrease in mRNA and protein expression was observed in 293T cells transfected with plasmids carrying the LMF1 c.1523C > T mutation. Subcellular localization showed that both wild-type (WT) and mutant LMF1 protein were localized at the cell cytoplasm. In the cell medium and cell lysates, these LMF1 and LPL gene mutations both caused a decreased LPL mass. Moreover, the combination of LMF1 and LPL gene mutations significantly decreased LPL levels compared to their individual effects on the LPL concentration. Both the clinical and in vitro data suggest that severe hypertriglyceridemia was of digenic origin caused by LMF1 and LPL mutation double heterozygosity in this patient.

A novel sandwich-like MnO2/g-C3N4 nanocomposite (NC) based on the integration of high-density MnO2 nanorods (NRs) onto the surfaces of two-dimensional (2D) g-C3N4 sheets has been successfully fabricated through a facile soft chemical route at low temperature. The MnO2/g-C3N4 NC electrode enhanced the supercapacitor (SC) performance, benchmarked against both the bare MnO2 NRs electrode and the MnO2/graphene oxide (GO) NC electrode, exhibiting high specific capacitance of 211 F/g at a current density of 1 A/g, with good rate capacity and cycling stability. The sandwich-like hybrid structure, the unique 2D structure of the g-C3N4 sheets and the presence of nitrogen in the g-C3N4 all contributed to the promising SC performance of the MnO2/g-C3N4 NC. This work demonstrated the advantages of the g-C3N4 sheets over the commonly-used GO sheets in the design of novel hybrid composite for enhanced capacitance performance of MnO2-based electrochemical SCs, and the results could be extended to other electrode materials for SCs. [ABSTRACT FROM AUTHOR]