Metagenomic next-generation sequencing (mNGS) and droplet digital PCR (ddPCR) have recently demonstrated a great potential for pathogen detection. However, few studies have been undertaken to compare these two nucleic acid detection methods for identifying pathogens in patients with bloodstream infections (BSIs). This prospective study was thus conducted to compare these two methods for diagnostic applications in a clinical setting for critically ill patients with suspected BSIs. Upon suspicion of BSIs, whole blood samples were simultaneously drawn for ddPCR covering 20 common isolated pathogens and four antimicrobial resistance (AMR) genes, mNGS, and blood culture. Then, a head-to-head comparison was performed between ddPCR and mNGS. A total of 60 episodes of suspected BSIs were investigated in 45 critically ill patients, and ddPCR was positive in 50 (83.3%), mNGS in 41 (68.3%, not including viruses), and blood culture in 10 (16.7%) episodes. Of the 10 positive blood cultures, nine were concordantly identified by both mNGS and ddPCR methods. The head-to-head comparison showed that ddPCR was more rapid (~4 h vs. ~2 days) and sensitive (88 vs. 53 detectable pathogens) than mNGS within the detection range of ddPCR, while mNGS detected a broader range of pathogens (126 vs. 88 detectable pathogens, including viruses) than ddPCR. In addition, a total of 17 AMR genes, including 14 blaKPC and 3 mecA genes, were exclusively identified by ddPCR. Based on their respective limitations and strengths, the ddPCR method is more useful for rapid detection of common isolated pathogens as well as AMR genes in critically ill patients with suspected BSI, whereas mNGS testing is more appropriate for the diagnosis of BSI where classic microbiological or molecular diagnostic approaches fail to identify causative pathogens.

Leukocyte interleukin-3 receptor α (CD123) is regarded as a marker of leukemia stem cells. We previously found that CD123 was also highly expressed on CD34(+)CD38(-) cells in myelodysplastic syndrome (MDS) patients, but it is unclear whether the level and the characteristics of CD34(+)CD38(-)CD123(+) cells in MDS are similar to those in acute myeloid leukemia (AML). Based on previous research by our team, we further enlarged the specimens and found that the mean proportion and the mean MFI of CD34(+)CD38(-)CD123(+) cells in low-grade MDS were lower than that in AML, and those in high-grade MDS were similar to those in AML. CD34(+)CD38(-)CD123(+) cells expressed lower granulocyte stimulating factor receptor, CD11b, and apoptosis molecule (Annexin V), meanwhile, these cells showed upregulation of transcription factors (GATA-1, GATA-2) and transferrin receptor (CD71) in MDS and AML. Furthermore, an increase in CD34(+)CD38(-)CD123(+) cells was closely related to the number of cytopenias involving hematopoietic lineages, anemia, blast count in bone marrow smear, fluorescence in situ hybridization analysis and WHO prognostic scoring system score. Thus, increases in CD34(+)CD38(-)CD123(+) cells may reflect malignant clonal cells with aberrant differentiation, overproliferation, and decreased apoptosis in MDS, which were similar to AML. CD123 may thus be a promising indicator for identifying malignant clonal cells in MDS and a candidate for targeted therapy.

No abstract

Tubular damage initiated by inflammatory response and ischemic/hypoxic stress is a hallmark of septic acute kidney injury (AKI), albeit the molecular mechanism coupling the two events remains unclear. We investigated the intrinsic nature of tubular damage with respect to inflammatory/hypoxic stress during septic AKI. Methods: The apoptotic response of tubular cells to LPS stimuli was analyzed before and after hypoxia exposure. Cellular ubiquitination, co-immunoprecipitation, GST-pulldown, in vitro protein kinase assay, immunofluorescence and CRISPR technology were adopted to determine the molecular mechanism underlying this process. In vivo characterization was performed in wild-type and DAPK1 -/- mice models of cecal ligation and puncture (CLP). Results: We found that the MyD88-dependent inflammatory response couples to tubular damage during LPS stimuli under hypoxia in a Fn14/SCF Fbxw7α -dispensable manner via recruitment of caspase-8 with TRIF-RIP1 signalosome mediated by DAPK1, which directly binds to and phosphorylates Pellino1 at Ser39, leading to Pellino1 poly-ubiquitination and turnover. Either pharmacological deactivation or genetic ablation of DAPK1 makes tubular cells refractory to the LPS-induced damage in the context of hypoxia, while kinase activity of DAPK1 is essential for ruin execution. Targeting DAPK1 effectively protects mice against septic AKI and potentiates the efficacy of a MyD88 homodimerization inhibitor, ST2825. Conclusion: Our findings provide a rationale for the mechanism whereby inflammation intersects with hypoxic tubular damage during septic AKI through a previously unappreciated role of DAPK1-inducible Ser39 phosphorylation in Pellino1 turnover and underscore that combined targeting DAPK1 and MyD88 might be a feasible strategy for septic AKI management.