Daily Sepsis Research Analysis
Three studies advance sepsis research across diagnosis and therapeutics: single-vesicle urinary proteomics identifies CD35 as a high-performing biomarker for sepsis-associated acute kidney injury, a natural-experiment cohort links early anti-anaerobic antibiotics to higher AKI risk, and soluble Neuropilin-1 shows promise for distinguishing bacterial from viral sepsis. Together, they inform biomarker-driven risk stratification and antibiotic stewardship.
Summary
Three studies advance sepsis research across diagnosis and therapeutics: single-vesicle urinary proteomics identifies CD35 as a high-performing biomarker for sepsis-associated acute kidney injury, a natural-experiment cohort links early anti-anaerobic antibiotics to higher AKI risk, and soluble Neuropilin-1 shows promise for distinguishing bacterial from viral sepsis. Together, they inform biomarker-driven risk stratification and antibiotic stewardship.
Research Themes
- Early biomarkers for sepsis-associated acute kidney injury
- Antibiotic stewardship and microbiome-mediated toxicity
- Differentiating bacterial versus viral sepsis
Selected Articles
1. Bacterial Infections Shape Cardiac Macrophages' Response to Ischemia.
Prior bacteremia durably reprograms cardiac macrophage compartments, leaving two distinct subpopulations that persist after infection resolution. A chemotactic subset amplifies leukocyte recruitment and inflammation during subsequent myocardial ischemia, which can be mitigated by macrophage-targeted RNA interference.
Impact: This rigorous mechanistic study links antecedent bacteremia to heightened myocardial inflammatory responses via durable reprogramming of cardiac macrophages, revealing targetable pathways. It provides a biological basis for infection-ischemia interactions with therapeutic implications.
Clinical Implications: Identifying infection-primed inflammatory macrophage subsets suggests opportunities to risk-stratify post-infection patients for cardiovascular events and to test macrophage-directed anti-inflammatory strategies after severe infections.
Key Findings
- Bacteremia induced a persistent expansion and compositional shift in cardiac macrophages, sustained over time.
- Two previously unrecognized macrophage subpopulations persisted post-infection; one exhibited heightened chemotaxis that amplified ischemic inflammation.
- Macrophage-targeted, nanoparticle-enabled RNA interference attenuated the disproportionate inflammatory response after subsequent myocardial ischemia.
Methodological Strengths
- Multi-modal mechanistic approach combining fate mapping, single-cell RNA-seq, and in vivo nanoparticle-mediated RNAi.
- Use of longitudinal assessments to demonstrate durable immune reprogramming after bacteremia.
Limitations
- Preclinical design limits direct generalizability to human patients.
- Clinical outcomes were modeled via experimental ischemia rather than observed in patients.
Future Directions: Translate findings to human cohorts to test whether post-infection macrophage signatures predict cardiovascular events and to evaluate macrophage-directed anti-inflammatory interventions.
BACKGROUND: Patients with bacterial infections are at increased risk for subsequent cardiovascular events. Whether infections' effects on innate immune cells within the cardiovascular system influence subsequent pathologies remains unclear. Here, we explore cardiac myeloid cells' chronic adaptations to a preceding bacterial insult and implications for subsequent myocardial ischemia. METHODS: We used various flow cytometry protocols to assess cardiac immune cells, peripheral leukocytes, and hematopoietic stem and progenitor cells in bone marrow and spleen. A genetic fate-mapping model was used to determine cardiac macrophages' origin after bacteremia. Cardiac leukocytes were analyzed using single-cell RNA sequencing. Nanoparticle-mediated RNA interference was used to target macrophages in vivo. RESULTS: Cardiac macrophage numbers increased sharply, and numerical changes alongside subset alterations persisted over time. Fate-mapping pointed toward local origin as the primary macrophage source after infection. Profiling macrophage heterogeneity using single-cell RNA sequencing, we identified two previously unknown subpopulations remaining after resolution of infection. While heightened metabolic activity was one subset's primary feature, the other displayed excessive chemotactic properties, which amplified cardiac leukocyte recruitment and inflammation after a subsequent ischemic injury. Targeting cardiac macrophages' surplus inflammatory activity after infection using nanoparticle-enabled, macrophage-directed RNA interference kept disproportionate subsequent ischemic inflammation at bay. CONCLUSIONS: Bacteremia induces long-lasting changes in the cardiovascular system's innate immune cells' composition. This may amplify myocardial inflammation after a subsequent ischemic injury.
2. Single urinary extracellular vesicle proteomics identifies complement receptor CD35 as a biomarker for sepsis-associated acute kidney injury.
Using single-vesicle proximity barcoding, the authors identify urinary EV CD35 as a robust biomarker for early diagnosis and risk stratification of SA-AKI. CD35-uEV achieved high AUCs for diagnosis, subclinical AKI detection, and prediction of persistent AKI, mortality, and AKD progression, with podocyte injury as the cellular source.
Impact: Introduces a single-vesicle urinary proteomics approach with strong diagnostic and prognostic performance for SA-AKI and traces biomarker origin to podocytes, advancing precision nephrology in sepsis.
Clinical Implications: CD35-uEV could support early detection of SA-AKI and stratify risk for persistent injury and mortality, informing monitoring intensity and nephroprotective strategies once clinically implemented.
Key Findings
- Urinary single-EV CD35 achieved AUC-ROC 0.89 for SA-AKI diagnosis in a validation cohort (n=134).
- CD35-uEV identified subclinical AKI in a prospective cohort (AUC-ROC 0.84; n=72).
- CD35-uEV levels predicted persistent AKI (AUC 0.77), mortality (AUC 0.70), and AKD progression (AUC 0.66), and were traced to injured podocytes by multi-omics.
Methodological Strengths
- Single-vesicle proximity-dependent barcoding assay enabling high-resolution urinary EV surface proteomics.
- Independent validation and prospective cohorts with clinically relevant endpoints; integration of multi-omics to define cellular origin.
Limitations
- Specialized assay platforms may limit immediate clinical adoption and require standardization.
- Sample sizes in validation/prospective cohorts are modest; external, multicenter validation is needed.
Future Directions: Validate CD35-uEV in multicenter clinical settings, standardize assay workflows, define decision thresholds, and test whether biomarker-guided care improves renal outcomes.
Sepsis-associated acute kidney injury (SA-AKI) portends severe health burden due to significant morbidity and mortality, while early diagnosis remains challenging. In this study, proximity-dependent barcoding assay (PBA) is established to profile the surface proteome of single urinary extracellular vesicle (uEV). Principle uEV clusters with unique function and origination are profiled in SA-AKI in a screening cohort. Complement receptor CD35 on single uEV (CD35-uEV) displays high diagnostic accuracy for SA-AKI (AUC-ROC 0.89 in validation cohort, n = 134). Besides, CD35-uEV enables identification of subclinical AKI (AUC-ROC 0.84 in prospective cohort, n = 72). Moreover, CD35-uEV correlates closely with AKI severity which also predicts persistent AKI (AUC-ROC 0.77), mortality risks (AUC-ROC 0.70) and progression to AKD (AUC-ROC 0.66). Multi-omics profiling reveals that CD35-uEV are predominantly released from injured podocytes exhibiting diminished CD35 expression. Overall, this study identifies a single uEV biomarker related to injured podocyte for early diagnosis and risk stratification of SA-AKI.
3. Anti-Anaerobic Antibiotics, Gut Microbiota, and Sepsis-associated Acute Kidney Injury.
In 12,776 septic patients, early exposure to anti-anaerobic antibiotics was independently associated with a 61% higher risk of sepsis-associated AKI. Instrumental variable analyses leveraging the 2015–2016 piperacillin–tazobactam shortage support a likely causal link, implicating microbiome disruption.
Impact: Large-scale natural-experiment analyses connect early anti-anaerobic coverage to AKI risk in sepsis, informing antibiotic stewardship and kidney-sparing strategies.
Clinical Implications: Avoiding routine early anti-anaerobic coverage unless clearly indicated may reduce SA-AKI risk; consider microbiome-sparing regimens and early nephroprotective monitoring for exposed patients.
Key Findings
- Retrospective cohort (N=12,776) showed early anti-anaerobic antibiotic exposure increased SA-AKI risk by 61% (95% CI 37–92%).
- Instrumental variable analyses exploiting a national piperacillin–tazobactam shortage supported a causal relationship.
- Findings suggest gut microbiome disruption as a mechanism linking anti-anaerobic coverage and AKI in sepsis.
Methodological Strengths
- Large sample size with multivariable adjustment and complementary instrumental variable analyses.
- Use of a natural experiment (drug shortage) to mitigate confounding by indication.
Limitations
- Retrospective design leaves potential for residual confounding and misclassification.
- Gut microbiome was not directly measured to confirm mechanistic pathways.
Future Directions: Prospective trials comparing microbiome-sparing versus anti-anaerobic regimens in sepsis with kidney outcomes, and mechanistic human microbiome studies.
RATIONALE: Acute kidney injury (AKI) is a common complication of sepsis. Anti-anaerobic antibiotics, which deplete gut commensal bacteria, are common in the initial management of sepsis. Recent studies have reported an association between anti-anaerobic antibiotics and mortality, but the mechanisms underlying this relationship remain unknown. OBJECTIVE: To determine whether anti-anaerobic antibiotics and gut microbiome disruption increase patient susceptibility to sepsis-associated AKI. METHODS: We identified a cohort of patients with sepsis and performed four complementary analyses: 1) comparing AKI incidence among patients who did and did not receive early anti-anaerobic antibiotics, 2-3) two instrumental variable analyses using the 2015-16 piperacillin-tazobactam shortage to determine the effect of anti-anaerobic antibiotics on the MEASUREMENTS AND MAIN RESULTS: In a retrospective cohort study (N=12,776), early exposure to anti-anaerobic antibiotics was independently associated with a 61% increased risk of sepsis-associated AKI (95% CI-37%-92%). In instrumental variable analyses of AKI CONCLUSIONS: Anti-anaerobic antibiotics are associated with increased risk of AKI in sepsis, potentially via modulation of the gut microbiome.
4. Soluble Neuropilin-1 as a Marker for Distinguishing Bacterial and Viral Sepsis in Critically Ill Patients-A Prospective, Multicenter, Observational Study.
In a prospective two-center cohort of critically ill adults, sNRP-1 trajectories differentiated bacterial from viral sepsis: IL-6, PCT, and CRP declined over time, whereas sNRP-1 remained elevated in bacterial sepsis throughout ICU stay.
Impact: Provides time-course evidence that sNRP-1 may complement or outperform conventional markers for etiologic differentiation in sepsis, guiding antimicrobial stewardship.
Clinical Implications: Incorporating sNRP-1 trajectories with standard markers could improve early etiologic classification of sepsis and reduce unnecessary broad-spectrum antibiotics.
Key Findings
- Prospective, two-center study in SEPSIS-3 adults compared 7-day biomarker trajectories in bacterial vs viral sepsis.
- IL-6, PCT, and CRP declined over time, but sNRP-1 remained persistently elevated in bacterial sepsis throughout ICU stay.
- sNRP-1 thus offers complementary discriminatory value when conventional inflammatory markers fall.
Methodological Strengths
- Prospective multicenter design with serial biomarker measurements over 7 days.
- Head-to-head temporal comparison with established markers (IL-6, PCT, CRP).
Limitations
- Exact sample size and diagnostic performance metrics (e.g., AUC, thresholds) are not reported in the abstract.
- Exclusion of immunosuppressed patients may limit generalizability to broader ICU populations.
Future Directions: Quantify diagnostic accuracy (AUC, cutoffs) across larger, diverse cohorts; evaluate impact on antibiotic decision-making and patient outcomes.
Sepsis causes millions of deaths each year. Rapid, targeted therapy can reduce mortality rates. Both bacterial and viral pathogens can trigger sepsis, but the utility of commonly used inflammatory markers for differentiation remains controversial. Moreover, little is known about the time courses of alternative inflammatory parameters. The aim of this prospective, two-center observational study was to investigate the differences in the course of soluble Neuropilin-1 (sNRP-1) levels between bacterial and viral sepsis over a 7-day period. To be included, adult patients had to meet the SEPSIS-3 criteria and be diagnosed with either a bacterial or viral pathogen. Immunosuppressed patients were excluded. While IL-6, PCT, and CRP levels decreased consistently over time, sNRP-1 levels remained elevated in the bacterial group throughout the entire ICU stay. PCT (