Daily Sepsis Research Analysis

Bacterial lipopolysaccharide (LPS) is among the most potent pathogen-associated molecular patterns (PAMPs). In animals, LPS can induce endotoxic shock, a widely used model of sepsis. Studies of this system have yielded important insights into innate immunity, including key immune sensors and signaling pathways. However, how inflammatory pathways are spatially coordinated across cell types and organs in vivo during endotoxic shock remains poorly understood. Here, we systematically analyzed LPS-induced lethality in mice to define the coordinated contributions of cell death pathways, inflammatory cytokines, and lipid mediators to endotoxic shock pathology. We found that caspase-11 signaling acts primarily in nonhematopoietic cells and drives tissue injury, whereas caspase-8 and RIPK3 function predominantly in hematopoietic cells and are both controlled by TRIF. Although proinflammatory cytokines are thought to promote cell death, it is surprising that cell death and/or components of death signaling are critical for initiating the cytokine storm because disruption of these cell death pathways markedly and preferentially reduces LPS-induced cytokine production in vivo. Combined deficiency of caspase-11, RIPK3, and caspase-8 fully protected mice from LPS-induced death, and additional cyclooxygenase inhibition eliminated remaining sickness behaviors such as reduced mobility. Together, these interventions rendered LPS-treated mice nearly indistinguishable from healthy controls. Overall, we delineate the core of the integrated signaling network that governs the pathological manifestations of LPS-induced endotoxic shock in mice.

BACKGROUND: Sepsis is a severe inflammatory condition often complicated by acute lung injury (ALI) with limited therapeutic options. S100 Calcium Binding Protein A9 (S100A9) as an alarmin is highly elevated in sepsis. We observed that S100A9 was lactylated in the lung tissues of septic mice, the role of which in regulating sepsis-related ALI remains unknown. METHODS: S100A9 lactylation sites were identified in septic patients and CLP mice using immunoprecipitation and mass spectrometry. Mechanistic studies employed mutagenesis, co-immunoprecipitation, and luciferase assays. RESULTS: In this study, we confirmed that S100A9 was lactylated at K4 and K94 in septic patients. Lactylated S100A9 promoted its nuclear translocation, thereby enhancing its interaction with transcription factor CCAAT/enhancer-binding protein beta (Cebpb). The complex of S100A9 and Cebpb further promoted the transcriptional activation of downstream interleukin 1 beta (IL-1β), leading to sepsis-related ALI. Moreover, the knockout of S100A9 effectively alleviated sepsis-induced inflammatory response and lung injury. CONCLUSIONS: Our findings elucidated the importance of S100A9 lactylation in regulating inflammatory responses of macrophages in sepsis-induced ALI, providing novel insights into the pathophysiology of sepsis and potential therapeutic targets for sepsis-associated organ dysfunction.

Rapid and accurate identification of gram-positive bacteria that cause bloodstream infections using molecular assays drives antibiotic optimization and patient management. This multisite study evaluated the performance of LIAISON PLEX Gram-Positive Blood Culture (BCP) Assay, a qualitative multiplexed diagnostic molecular test that detects and differentiates 13 gram-positive bacterial targets and 4 antibiotic resistance markers (AMRs) from blood culture bottles showing gram-positive bacterial growth. Clinical performance was examined on 509 prospective, 162 pre-selected, and 225 contrived blood culture samples. The overall valid rate of the tests was 99.9%. The overall sensitivity/PPA and specificity/NPA for all targets were 98.5% and 99.7%, respectively. In the inclusivity study, 183 of 184 tested strains were detected. Cross-reactivity was observed in five bacteria among a collection of 103 off-panel species. The LIAISON PLEX BCP Assay demonstrated compatibility with various types of blood culture bottles by three manufacturers. Target organism detection was not affected by the presence of six potential interfering substances. Both sensitivity and specificity were maintained in the setting of polymicrobial infections with different organisms. The LIAISON PLEX BCP Assay allows fast detection of gram-positive organisms and their AMR genes from positive blood cultures with high accuracy and reliability.IMPORTANCEThe use of molecular assays has improved the diagnosis of bloodstream infections because of their much-reduced turnaround time and high performance compared to conventional culture workups. The early detection of clinically significant resistance markers has direct impacts on antibiotic optimization and patient isolation. This multisite study demonstrated excellent sensitivity and specificity of the LIAISON PLEX Gram-Positive Blood Culture Assay that detects and differentiates 13 gram-positive bacterial targets and 4 antibiotic resistance markers. The assay performance was assessed clinically and analytically using large and diverse sets of samples.