Evolving Concepts in Sepsis Definitions

Advances and Challenges in Sepsis Management: Modern Tools and Future Directions

Sepsis, a critical condition marked by systemic inflammation, profoundly impacts both innate and adaptive immunity, often resulting in lymphopenia. This immune alteration can spare regulatory T cells (Tregs) but significantly affects other lymphocyte subsets, leading to diminished effector functions, altered cytokine profiles, and metabolic changes. The complexity of sepsis stems not only from its pathophysiology but also from the heterogeneity of patient responses, posing significant challenges in developing universally effective therapies. This review emphasizes the importance of phenotyping in sepsis to enhance patient-specific diagnostic and therapeutic strategies. Phenotyping immune cells, which categorizes patients based on clinical and immunological characteristics, is pivotal for tailoring treatment approaches. Flow cytometry emerges as a crucial tool in this endeavor, offering rapid, low cost and detailed analysis of immune cell populations and their functional states. Indeed, this technology facilitates the understanding of immune dysfunctions in sepsis and contributes to the identification of novel biomarkers. Our review underscores the potential of integrating flow cytometry with omics data, machine learning and clinical observations to refine sepsis management, highlighting the shift towards personalized medicine in critical care. This approach could lead to more precise interventions, improving outcomes in this heterogeneously affected patient population.

A Machine Learning Understanding of Sepsis

Sepsis is a serious cause of morbidity and mortality and yet its pathophysiology remains elusive. Recently, medical and technological advances have helped redefine the criteria for sepsis incidence, which is otherwise poorly understood. With the recording of clinical parameters and outcomes of patients, enabling technologies, such as machine learning, open avenues for early prognostic systems for sepsis. In this work, we propose a two-phase approach towards prognostic scoring by predicting two outcomes in sepsis patients - Sepsis Severity and Comorbidity Severity. We train and evaluate multiple machine learning models on a dataset of 80 parameters collected from 800 patients at Amrita Institute of Medical Sciences, Kerala, India. We present an analysis of these results and harmonize consistencies and/or contradictions between elements of human knowledge and that of the model, using local interpretable model-agnostic explanations and other methods.

Analytical and clinical validation of a microbial cell-free DNA sequencing test for infectious disease

Thousands of pathogens are known to infect humans, but only a fraction are readily identifiable using current diagnostic methods. Microbial cell-free DNA sequencing offers the potential to non-invasively identify a wide range of infections throughout the body, but the challenges of clinical-grade metagenomic testing must be addressed. Here we describe the analytical and clinical validation of a next-generation sequencing test that identifies and quantifies microbial cell-free DNA in plasma from 1,250 clinically relevant bacteria, DNA viruses, fungi and eukaryotic parasites. Test accuracy, precision, bias and robustness to a number of metagenomics-specific challenges were determined using a panel of 13 microorganisms that model key determinants of performance in 358 contrived plasma samples, as well as 2,625 infections simulated in silico and 580 clinical study samples. The test showed 93.7% agreement with blood culture in a cohort of 350 patients with a sepsis alert and identified an independently adjudicated cause of the sepsis alert more often than all of the microbiological testing combined (169 aetiological determinations versus 132). Among the 166 samples adjudicated to have no sepsis aetiology identified by any of the tested methods, sequencing identified microbial cell-free DNA in 62, likely derived from commensal organisms and incidental findings unrelated to the sepsis alert. Analysis of the first 2,000 patient samples tested in the CLIA laboratory showed that more than 85% of results were delivered the day after sample receipt, with 53.7% of reports identifying one or more microorganisms.

Protective Effects of Live Combined B. subtilis and E. faecium in Polymicrobial Sepsis Through Modulating Activation and Transformation of Macrophages and Mast Cells

Aims: Clinical studies showed that the use of probiotics during critical illness reduced nosocomial infection and improved clinical outcome. However, the functional mechanisms of probiotics is remains unclear. Therefore the aim of current study is to explore the protective effects and understand the underlying mechanisms for the beneficial effects of live combined Bacillus subtilis and Enterococcus faecium (LCBE) in cecal ligation puncture (CLP)-induced sepsis.

Methods and Results: Seven-week-old C57BL/6J mice were divided into three groups: sham group (6 mice), CLP-control group (20 mice, pretreatment with saline for 7 days before CLP surgery) and CLP-probiotics group (14 mice, pretreatment with LCBE enteric-coated capsules for 7 days before CLP surgery). In survival experiment, mice were monitored for 7 days after CLP. After the procedure, mice were sacrificed, and, serum, and peritoneal lavage fluid were collected and intestinal ileal samples were harvested.

Results: Our results showed that the mortality was significantly reduced in mice CLP-probiotics group vs. CLP-control group (P < 0.05). Also, treatment CLP-probiotics group decreased the injury scores CLP-probiotics group when compared to CLP-control group. Additionally, levels of pro-inflammatory cytokines IL-6 and TNF-α levels in the serum and intestinal ileal tissues of CLP-probiotics group were reduced when compared to CLP-control group (P < 0.05). However, no significant differences in anti-inflammatory levels of IL-10 and TGF-β1 were observed between CLP-control and CLP-probiotic groups. Furthermore, our experiments showed that that probiotic treatment suppressed the macrophage activation and transformation from M-type to M1-type, inhibited the mast cells (MCs) degranulation, and activation of AKT (kinase B) pathway.

Conclusion: In conclusion, our data shows that probiotics have a protective role in CLP septic mice through reducing intestinal inflammation, altering macrophage polarization and MCs degranulation, and regulating AKT signaling.

Significance and Impact of Study: This study demonstrated the protective effects and mechanisms involved in the protective role of live combined Bacillus subtilis and Enterococcus faecium (LCBE) in CLP-induced septic mice model.

Preadministration of Hydrogen-Rich Water Protects Against Lipopolysaccharide-Induced Sepsis and Attenuates Liver Injury

Despite significant advances in antibiotic therapy and intensive care, sepsis remains the most common cause of death in intensive care units. We previously reported that molecular hydrogen (H2) acts as a therapeutic and preventive antioxidant. Here, we show that preadministration of H2-dissolved water (HW) suppresses lipopolysaccharide (LPS)-induced endotoxin shock in mice. Drinking HW for 3 days before LPS injection prolonged survival in a mouse model of sepsis. The H2 concentration immediately increased in the liver but not in the kidney after drinking HW. The protective effects of the preadministration of HW on LPS-induced liver injury were examined. Twenty-four hours after LPS injection, preadministration of HW reduced the increase in both apoptosis and oxidative stress. Moreover, preadministration of HW enhanced LPS-induced expression of heme oxyganase-1 and reduced endothelin-1 expression. These results indicate the therapeutic potential of HW in preventing acute injury of the liver with attenuation of an increase in oxidative stress. HW is likely to trigger adaptive responses against oxidative stress.

Association of HLA-G 3'UTR polymorphisms and haplotypes with severe sepsis in a Brazilian population

BACKGROUND

The human leukocyte antigen G (HLA-G) is a molecule involved in immune system modulation, acting in the maintenance of a state of immune tolerance. Some polymorphisms in the HLA-G gene 3' untranslated region (3'UTR) were associated to distinct levels of HLA-G expression and to sepsis development. In the present study, haplotypes and polymorphisms of the HLA-G 3'UTR were analyzed in Brazilian septic patients.

METHODS

The HLA-G 3'UTR was amplified by PCR, sequenced and eight polymorphisms were genotyped (the 14bp insertion/deletion, +3003T/C, +3010C/G, +3027A/C, +3035C/T, +3142G/C, +3187A/G and+3196C/G) in DNA samples from septic patients (with severe sepsis or septic shock) and controls. The haplotypes were inferred and association tests were performed through Chi square test and binary logistic regression.

RESULTS

The+3027AC genotype was associated asa risk factor to sepsis development (OR 3.17, P_Bonferroni 0.048). Further, the presence of the UTR-7 haplotype (OR 2.97, P_Bonferroni 0.018), and of 14bp-Ins_+3142G_+3187A haplotype (OR 2.39, P_Bonferroni 0.045) were associated with sepsis, conferring susceptibility.

CONCLUSION

Our data confirm an important role of HLA-G 3'UTR polymorphisms in the development of severe forms of sepsis (severe sepsis and septic shock). The genotyping of HLA-G genetic variants and haplotypes could be useful as a prediction tool of increased risk to severe sepsis.

New Consensus Definitions for Sepsis and Septic Shock: Implications for Treatment Strategies and Drug Development?

Sepsis continues to escape a precise diagnostic definition. The most recent consensus definition, termed Sepsis-3, highlights the importance of the maladaptive and potentially life-threatening host response to infection. After briefly reviewing the history and epidemiology of sepsis, we go on to describe some of the challenges encountered when classifying such a heterogenous disease state. In the context of these new definitions for sepsis and septic shock, we explore current and potentially novel therapies, and conclude by mentioning some of the controversies of this most recent framework.

Challenges in Sepsis Care: New Sepsis Definitions and Fluid Resuscitation Beyond the Central Venous Pressure

There are two important recent changes in sepsis care. The first key change is the 2016 Sepsis-3 definitions from the recent consensus workgroup with new sepsis and septic shock definitions. Useful tools for assessing patients that have a greater risk of mortality include Sequential Organ Failure Assessment (SOFA) in intensive care units and quick SOFA outside intensive care units. The second change involves management of fluid resuscitation and measures of volume responsiveness. Measures such as blood pressure and central venous pressure are not reliable. Fluid challenges and responsiveness should be based on stroke volume change of greater than 10%.

The C-terminal Domain Supports a Novel Function for CETPI as a New Plasma Lipopolysaccharide-Binding Protein

Described by our group a few years ago, the cholesteryl-ester transfer protein isoform (CETPI), exclusively expressed in the small intestine and present in human plasma, lacked a functional identification for a role of physiological relevance. Now, this study introduces CETPI as a new protein with the potential capability to recognise, bind and neutralise lipopolysaccharides (LPS). Peptides derived from the C-terminal domain of CETPI showed that CETPI not only might interact with several LPS serotypes but also might displace LPS bound to the surface of cells. Peptide VSAK, derived from the last 18 residues of CETPI, protected against the cytotoxic effect of LPS on macrophages. At high concentrations, when different cell types were tested in culture, it did not exhibit cytotoxicity by itself and it did prevent the expression of pro-inflammatory cytokines as well as the generation of oxidative stress conditions. In a rabbit model of septic shock, the infusion of peptide VSAK exerted a protective effect against the effects of LPS and reduced the presence of tumor necrosis factor-alpha (TNFα) in plasma. Therefore, CETPI is proposed as a new protein with the capability to advance the possibilities for better understanding and treatment of the dangerous effects of LPS in vivo.

Toll-like receptor 4 is involved in bacterial endotoxin-induced endothelial cell injury and SOC-mediated calcium regulation

Bacterial endotoxins may lead to vascular endothelial cell injury. Our study explored the role of TLR4 (Toll-like receptor 4) and STIM1 (stromal interaction molecule 1) in bacterial endotoxin-induced calcium overload and inflammatory reactions in HUVECs (human umbilical vein endothelial cells). It showed that under LPS (lipopolysaccharide) stimulation, LBP (LPS-binding protein) mRNA levels peaked at 24 h, TLR4 levels at 12 h and NF-κB (nuclear factor κB) levels at 6 h (all P<0.01). LBP levels increased gradually and peaked at 24 h of LPS treatment. TLR4 protein levels increased significantly at 1 h and peaked at 12 h. NF-κB protein levels markedly increased at 1 h and peaked at 6 h. Knockdown of STIM1 alone, TLR4 alone or both STIM1 and TLR4 together, markedly abolished LPS-induced increase in calcium influx into cells (P<0.05, P<0.01 and P<0.01 respectively). LBP-TLR4 and STIM-NF-κB interactions were detected without LPS treatment, enhanced by LPS stimulation, and markedly reduced by knocking down TLR4 and STIM respectively. Both the NF-κB inhibitor, PDTC (pyrrolidine dithiocarbamate) and TLR4 knockdown could block LPS induction of NF-κB, STIM, TNFα (tumour necrosis factor α) and IL-6 (interleukin 6). The data indicate LPS-LBP may activate TLR4 signalling and downstream transcription factor NF-κB, which further can activate STIM1 and eventually lead to calcium influx and injury of HUVECs. Inhibition of TLR4 effectively reverses LPS induction of inflammatory mediator generation and extracellular calcium influx mediated by STIM1.

High mortality associated with hyperglycemia, neutrophilia, and lymphopenia in critically ill patients

A common finding in patients admitted to an Intensive Care Unit (ICU) is hyperglycemia without prior history of diabetes. This increase in blood glucose is considered a negative prognostic factor for patients in the ICU. Hence, we performed a retrospective cohort study in patients admitted at the ICU of the National Institute of Respiratory Diseases (INER) in a 7-month period; we collected data about their blood glucose concentration during their stay at the ICU. We gathered the available medical records of 30 patients out of 58 admitted to the ICU. Among the 30 patients, 21 patients survived (70%) and 9 patients with community-acquired pneumonia (CAP) died (30%). The 21 surviving patients included 17 patients with acute respiratory distress secondary to CAP and 4 patients with asthmatic crisis upon admission to the ICU. After admission, all patients progressed to sepsis and showed an increase in blood glucose. We detected higher glucose concentrations in deceased patients (147 mg/dl ± 4.23), as compared to surviving patients (129 mg/dl ± 2.17) (P < 0.001). In addition, the percentage of lymphocytes was lower in deceased patients than that in surviving patients (5.7 vs. 11.8%, P < 0.001), whereas percentage of neutrophils was elevated in the deceased patients (90.7 vs. 80.9%, P < 0.001). It is therefore important to measure continuously glucose concentrations, as well as the numbers of neutrophils and lymphocytes in critically ill patients with hyperglycemia. Such a simple monitoring plan may prevent fatal complications in patients admitted to ICU.

Organ failure avoidance and mitigation strategies in surgery

Postoperative organ failure is a challenging disease process that is better prevented than treated. Providers should use close observation and clinical judgment, and checklists of best practices to minimize the risk of organ failure in their patients. The treatment of multiorgan dysfunction syndrome (MODS) generally remains supportive, outside of rapid initiation of source control (when appropriate) and targeted antibiotic therapy. More specific treatments may be developed as the complex pathophysiology of MODS is better understood and more homogenous patient populations are selected for study.