Clinical gram-positive sepsis: does it fundamentally differ from gram-negative bacterial sepsis?

Deep learning model to discriminate diverse infection types based on pairwise analysis of host gene expression

Accurate detection of pathogens, particularly distinguishing between Gram-positive and Gram-negative bacteria, could improve disease treatment. Host gene expression can capture the immune system's response to infections caused by various pathogens. Here, we present a deep neural network model, bvnGPS2, which incorporates the attention mechanism based on a large-scale integrated host transcriptome dataset to precisely identify Gram-positive and Gram-negative bacterial infections as well as viral infections. We performed analysis of 4,949 blood samples across 40 cohorts from 10 countries using our previously designed omics data integration method, iPAGE, to select discriminant gene pairs and train the bvnGPS2. The performance of the model was evaluated on six independent cohorts comprising 374 samples. Overall, our deep neural network model shows robust capability to accurately identify specific infections, paving the way for precise medicine strategies in infection treatment and potentially also for identifying subtypes of other diseases.

Prognostic differences in sepsis caused by gram-negative bacteria and gram-positive bacteria: a systematic review and meta-analysis

BACKGROUND

Bacteria are the main pathogens that cause sepsis. The pathogenic mechanisms of sepsis caused by gram-negative and gram-positive bacteria are completely different, and their prognostic differences in sepsis remain unclear.

METHODS

The PubMed, Web of Science, Cochrane Library, and Embase databases were searched for Chinese and English studies (January 2003 to September 2023). Observational studies involving gram-negative (G (-))/gram-positive (G (+)) bacterial infection and the prognosis of sepsis were included. The stability of the results was evaluated by sensitivity analysis. Funnel plots and Egger tests were used to check whether there was publication bias. A meta-regression analysis was conducted on the results with high heterogeneity to identify the source of heterogeneity. A total of 6949 articles were retrieved from the database, and 45 studies involving 5586 subjects were included after screening according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Twenty-seven high-quality studies and 18 moderate-quality studies were identified according to the Newcastle‒Ottawa Scale score. There was no significant difference in the survival rate of sepsis caused by G (-) bacteria and G (+) bacteria (OR 0.95, 95% CI 0.70-1.28). Subgroup analysis according to survival follow-up time showed no significant difference. The serum concentrations of C-reactive protein (CRP) (SMD = 0.39, 95% CI 0.02-0.76), procalcitonin (SMD = 1.95, 95% CI 1.32-2.59) and tumor necrosis factor-alpha (TNF-α) (MD = 0.31, 95% CI 0.25-0.38) in the G (-) bacterial infection group were significantly higher than those in the G (+) bacterial infection group, but there was no significant difference in IL-6 (SMD = 1.33, 95% CI - 0.18-2.84) and WBC count (MD = - 0.15, 95% CI - 0.96-00.66). There were no significant differences between G (-) and G (+) bacteria in D dimer level, activated partial thromboplastin time, thrombin time, international normalized ratio, platelet count, length of stay or length of ICU stay. Sensitivity analysis of the above results indicated that the results were stable.

CONCLUSION

The incidence of severe sepsis and the concentrations of inflammatory factors (CRP, PCT, TNF-α) in sepsis caused by G (-) bacteria were higher than those caused by G (+) bacteria. The two groups had no significant difference in survival rate, coagulation function, or hospital stay. The study was registered with PROSPERO (registration number: CRD42023465051).

Association between corticosteroid use and 28-day mortality in septic shock patients with gram-negative bacterial infection: a retrospective study

Purpose

Although corticosteroids are recommended in the 2021 Surviving Sepsis Campaign (SSC) guidelines, evidence with respect to their effects on short-term mortality remains conflicting. We conducted this study to identify whether corticosteroids alter 28-day mortality in septic shock patients with gram-negative bacterial infection.

Materials and methods

A total of 621 patients with septic shock and gram-negative bacterial culture results were identified from the Medical Information Mart for Intensive Care IV (MIMIC-IV) database. Propensity score matching (PSM) was performed, and Kaplan-Meier survival curve analyses with log-rank tests were used to determine the relationship between corticosteroid use and the risk of 28-day mortality. Subgroup analyses were conducted to assess whether the conclusions were stable and reliable.

Results

Corticosteroid administration was associated with increased 28-day mortality in septic shock patients with gram-negative bacterial infection (log-rank test P = 0.028). The incidence of Stage 2 or 3 AKI and the rate of hospital mortality were higher among patients who received corticosteroids. The incidence of Stage 2 or 3 AKI in the early period significantly mediated the relationship between corticosteroid use and 28-day mortality [P =0.046 for the average causal mediation effect (ACME)]. Interaction tests indicated that the effect of corticosteroid use was maintained in patients with a neutrophil-to-lymphocyte ratio (NLR) of <20 (P-value for interaction = 0.027).

Conclusion

Systemic corticosteroid use could be harmful in septic shock patients with gram-negative bacterial infection, especially in patients with relatively low NLR.

Organism type of infection is associated with prognosis in sepsis: an analysis from the MIMIC-IV database

BACKGROUND

Sepsis has a high mortality rate, which is expensive to treat, and is a major drain on healthcare resources; it seriously impacts the quality of human life. The clinical features of positive or non-positive blood cultures have been reported, but the clinical features of sepsis with different microbial infections and how they contribute to clinical outcomes have not been adequately described.

METHODS

We extracted clinical data of septic patients with a single pathogen from the online Medical Information Mart for Intensive Care(MIMIC)-IV database. Based on microbial cultures, patients were classified into Gram-negative, Gram-positive, and fungal groups. Then, we analyzed the clinical characteristics of sepsis patients with Gram-negative, Gram-positive, and fungal infections. The primary outcome was 28-day mortality. The secondary outcomes were in-hospital mortality, the length of hospital stay, the length of ICU stay, and the ventilation duration. In addition, Kaplan-Meier analysis was used for the 28-day cumulative survival rate of patients with sepsis. Finally, we performed further univariate and multivariate regression analyses for 28-day mortality and created a nomogram for predicting 28-day mortality.

RESULTS

The analysis showed that bloodstream infections showed a statistically significant difference in survival between Gram-positive and fungal organisms; drug resistance only reached statistical significance for Gram-positive bacteria. Through univariate and multivariate analysis, it was found that both the Gram-negative bacteria and fungi were independent risk factors for the short-term prognosis of sepsis patients. The multivariate regression model showed good discrimination, with a C-index of 0.788. We developed and validated a nomogram for the individualized prediction of 28-day mortality in patients with sepsis. Application of the nomogram still gave good calibration.

CONCLUSIONS

Organism type of infection is associated with mortality of sepsis, and early identification of the microbiological type of a patient with sepsis will provide an understanding of the patient's condition and guide treatment.

Plasma Chemerin Is Induced in Critically Ill Patients with Gram-Positive Infections

Chemerin is a chemoattractant protein abundantly expressed in hepatocytes. Chemerin exerts pro- and anti-inflammatory effects and acts as a pro-resolving protein. Chemerin levels are low in patients with liver cirrhosis and are increased in sepsis. The aim of this study was to identify associations between plasma chemerin levels and underlying diseases as well as causes of severe illness. The cohort included 32 patients with liver cirrhosis who had low systemic chemerin, and who were not considered for further evaluation. Plasma chemerin levels were similar between the 27 patients with systemic inflammatory response syndrome (SIRS), the 34 patients with sepsis and the 63 patients with septic shock. Chemerin in plasma correlated with C-reactive protein and leukocyte count but not with procalcitonin, a clinical marker of bacterial infection. Plasma chemerin did not differ among patients with and without ventilation and patients with and without dialysis. Vasopressor therapy was not associated with altered plasma chemerin levels. Infection with severe acute respiratory syndrome coronavirus 2 had no effect on plasma chemerin levels. Baseline levels of plasma chemerin could not discriminate between survivors and non-survivors. Notably, Gram-positive infection was associated with higher chemerin levels. In summary, the current study suggests that plasma chemerin might serve as an early biomarker for the diagnosis of Gram-positive infections in patients with sepsis.

Clinical and laboratory findings to differentiate late-onset sepsis caused by Gram-negative vs Gram-positive bacteria among perterm neonates: A retrospective cohort study

PURPOSE

Late-onset sepsis (LOS) is a clinical condition that results in serious morbidity and mortality in preterm neonates. The aim of this study was to identify differences in clinical and laboratory findings of LOS caused by Gram-negative vs Gram-positive bacteria among perterm neonates and to evaluate the diagnostic accuracy of biomarkers.

METHODS

The retrospective cohort study included 649 preterm neonates with LOS assigned to either the Gram-positive group (n = 194, 29.89 %) or the Gram-negative group (n = 455, 70.11 %). Demographic data, serum levels of C-reactive protein (CRP), and complete blood counts at 0-24 h (T1), 24-48 h (T2), and 48-72 h (T3) were retrieved and compared.

RESULTS

At T1, T2, and T3, serum CRP levels were higher (p < 0.001), while platelet (PTL) counts were significantly lower (p < 0.001) in the Gram-negative group vs Gram-positive group. The area under the curve (AUC) of the PLT count was 0.688 (95 % confidence interval [CI] = 0.644-0.731) at T1, 0.795 (95 % CI = 0.743-0.848) at T2, and 0.785 (95 % CI = 0.739-0.831) at T3, indicating good discriminatory power, while the AUC of serum CRP was 0.654 (95 % CI = 0.61-0.697) at T1, 0.831 (95 % CI = 0.781-0.888) at T2, and 0.94 (95 % CI = 0.744-0.843) at T3.

CONCLUSIONS

Neonatal LOS caused by Gram-negative bacteria was associated with higher CRP and lower PLT levels. These results suggested that PLT and CRP values may be useful biomarkers to differentiate sepsis caused by Gram-negative vs Gram-positive bacteria among perterm neonates.

14-O-[(4,6-Diamino-pyrimidine-2-yl) thioacetyl] mutilin inhibits α-hemolysin and protects Raw264.7 cells from injury induced by methicillin-resistant S. aureus

A new pleuromutilin derivative, 14-O-[(4,6-Diaminopyrimidine-2-yl) thioacetyl] mutilin (DPTM), has been synthesized and proven to be a potent agent against Gram-positive pathogens, especially for Staphylococcus aureus (S. aureus). However, its pharmacological activities against α-hemolysin (Hla), a major virulence factor produced by S. aureus, and inflammations related to S. aureus are still unknown. In the present study, we investigated the DPTM inhibition activities against methicillin-resistant S. aureus (MRSA) Hla and protective efficacy of Raw264.7 cells from injury induced by MRSA. The results showed that DPTM with sub-inhibitory concentrations significantly inhibited Hla on the hemolysis of rabbit erythrocytes and down-regulated the gene expressions of Hla and agrA with a dose-dependent fashion. In Raw264.7 cells infected with MRSA, DPTM efficiently attenuated the productions of lactate dehydrogenase (LDH), nitric oxide (NO) and pro-inflammatory cytokines, as well as the express levels of nuclear factor-kappaB (NF-κB), nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2). Furthermore, DPTM inhibited the translocation of p-65 to nucleus in RAW264.7 cells infected by MRSA.

Ovine CD14- an Immune Response Gene Has a Role Against Gastrointestinal Nematode Haemonchus contortus-A Novel Report

CD14 (also known as the monocyte differentiation antigen) is an important immune response gene known to be primarily responsible for innate immunity against bacterial pathogens, and as a pattern recognition receptor (PRR), binds with LPS (endotoxin), lipoproteins, and lipotechoic acid of bacteria. So far very limited work has been conducted in parasitic immunology. In the current study, we reported the role of CD14 in parasitic immunology in livestock species (sheep) for the first time. Ovine CD14 is characterized as a horse-shoe shaped bent solenoid with a hydrophobic amino-terminal pocket for CD14 along with domains. High mutation frequency was observed, out of total 41 mutations identified, 23 mutations were observed to be thermodynamically unstable and 11 mutations were deleterious in nature, causing major functional alteration of important domains of CD14, an indication of variations in individual susceptibility for sheep against Haemonchus contortus infestations. In silico studies with molecular docking reveal a role of immune response against Haemonchus contortus in sheep, which is later confirmed with experimental evidence through differential mRNA expression analysis for sheep, which revealed better expression of CD14 in Haemonchus contortus infected sheep compared to that of non-infected sheep. We confirmed the above findings with supportive evidence through haematological and biochemical analyses. Phylogenetic analysis was conducted to assess the evolutionary relationship with respect to humans and it was observed that sheep may well be used as model organisms due to better genetic closeness compared to that of mice.

Regulation of in vivo delivery of nanomedicines by herbal medicines

Nanomedicines are of increasing scrutiny due to their improved efficacy and/or mitigated side effects. They can be integrated with many other therapeutics to further boost the clinical benefits. Among those, herbal medicines are arousing great interest to be combined with nanomedicines to exert synergistic effects in multifaceted mechanisms. The in vivo performance of nanomedicines which determines the therapeutic efficacy and safety is believed to be heavily influenced by the physio-pathological characters of the body. Activation of multiple immune factors, e.g., complement system, phagocytic cells, lymphocytes, and among many others, can affect the fate of nanomedicines in blood circulation, biodistribution, interaction with single cells and intracellular transport. Immunomodulatory effects and metabolic regulation by herbal medicines have been widely witnessed during the past decades, which alter the physio-pathological conditions and dramatically affect in vivo delivery of nanomedicines. In this review, we summarize recent progress of understanding on the in vivo delivery process of nanomedicines and analyze the major affecting factors that regulate the interaction of nanomedicines with organisms. We discuss the immunomodulatory roles and metabolic regulation by herbal medicines and their effects on in vivo delivery process of nanomedicines, as well as the prospective clinical benefits from the combination of nanomedicines and herbal medicines.

Therapeutic Rationale for Endotoxin Removal with Polymyxin B Immobilized Fiber Column (PMX) for Septic Shock

Endotoxin removal therapy with polymyxin B immobilized fiber column (PMX) has been clinically applied for sepsis and septic shock patients since 1994. The effectiveness and usefulness of this therapy have been demonstrated for more than a quarter of a century. However, a documented survival benefit has not yet been demonstrable in a large, multicenter, randomized and controlled trial. Following the findings derived from a large sepsis clinical trial with PMX in North America, a new trial is ongoing to determine if PMX has a long-term survival benefit when administered to septic patients. Another approach to support a survival benefit from intervention with PMX is to utilize a detailed analysis available from a large clinical data base. The endotoxin adsorption capacity of PMX columns in vitro and the effectiveness of PMX columns can be further demonstrable in animal models. The capability of PMX and details of its mechanism of action to intervene in the sepsis cascade and impede organ dysfunction in septic patients is not fully understood. The surface antigen expression in monocytes and neutrophils are improved after PMX therapy. Immunomodulatory effects as a result of endotoxin removal and/or other mechanisms of action have been suggested. These effects and other potential immune effects may explain some of the improved effects upon organ dysfunction of sepsis and septic shock patients. Endotoxemia may be involved in the pathophysiology of other diseases than sepsis. A rapid diagnostic method to detect and target endotoxemia could allow us to practice precision medicine and expand the clinical indications of endotoxin removal therapy.

Combined targeting of vascular endothelial growth factor C (VEGFC) and P65 using miR-27b-3p agomir and lipoteichoic acid in the treatment of gastric cancer

Background

Gastric cancer is the second leading cancer-related mortality worldwide and more effective treatment strategies are urgently needed to combat the disease. Using lipoteichoic acid (LTA) and miR-27b-3p agomir, we aimed to assess the efficacy of this combination of therapies in treating gastric cancer.

Methods

The RNA levels of miR-27b-3p, FOXO3, MET, KRAS, vascular endothelial growth factor C (VEGFC), TSC1, and P65 were analyzed by quantified-PCR (Q-PCR) and the cell viability of AGS cells was analyzed by MTT. Confirm Luciferase reporter assays were used to explore the putative miR-27b-3p binding sites and Western blot analyzed the protein level of GAPDH, VEGFC, P65, AKT, and phosphorylated-AKT (p-AKT). The level of P65 in both the cytoplasm and nucleus of AGS cells was visualized by immunofluorescence assay. Subcutaneous xenograft models of gastric cancer were established, and mice were treated with miR-27b-3p agomir, LTA, or both. Hematoxylin-eosin staining and Ki-67 immunohistochemistry analysis of tumor tissues were then performed.

Results

The results showed that the decreased expression of miR-27b-3p in gastric cancer cell lines inhibited the viability of AGS cells, and VEGFC was confirmed as the target of miR-27b-3p. In addition, ectopic expression of miR-27b-3p significantly inhibited the AKT pathway in AGS and N87 cells, and LTA suppressed the proliferation of gastric cancer cells by inhibiting the NF-κB pathway. In an established xenograft model, both miR-27b-3p agomir alone and LTA treatment alone inhibited tumor growth and treatment which combined the two showed an even stronger inhibitory effect.

Conclusions

Taken together, the combined use of LTA and miR-27b-3p agomir exhibited a synergistic effect in the treatment of gastric cancer.

UiO-66-NH2 as an effective solid support for quinazoline derivatives for antibacterial agents against Gram-negative bacteria

UiO-66-NH2 is used as an effective drug carrier for the control of quinazoline release for antibacterial agents against Gram-negative bacteria.

An update on endotoxin neutralization strategies in Gram-negative bacterial infections

INTRODUCTION

Gram-negative bacterial infections represent still a severe problem of human health care, regarding the increase in multi-resistance against classical antibiotics and the lack of newly developed antimicrobials. For the fight against these germs, anti-infective agents must overcome and/or bind to the Gram-negative outer membrane consisting of a lipopolysaccharide (LPS, endotoxin) outer leaflet and an inner leaflet from phospholipids, with additional peripheral or integral membrane proteins (OMP's).

AREAS COVERED

The current article reviews data of existing therapeutic options and summarizes newer approaches for targeting and neutralizing endotoxins, ranging from in vitro over in vivo animal data to clinical applications by using databases such as Medline.

EXPERT OPINION

Conventional antibiotic treatment of the bacteria leads to their killing, but not necessary LPS neutralization, which may be a severe problem in particular for the systemic pathway. This is the reason why there is an increasing number of therapeutic approaches, which - besides combating whole bacteria - at the same time try to neutralize endotoxin within or outside the bacterial cells mainly responsible for the high inflammation induction in Gram-negative species.

Predictive Validity of the qSOFA Score for Sepsis in Adults with Community-Onset Staphylococcal Infection in Thailand

The quick sequential organ failure assessment (qSOFA) score has had limited validation in lower resource settings and was developed using data from high-income countries. We sought to evaluate the predictive validity of the qSOFA score for sepsis within a low- and middle-income country (LMIC) population with culture-proven staphylococcal infection. This was a secondary analysis of a prospective multicenter cohort in Thailand with culture-positive infection due to Staphylococcus aureus or S. argenteus within 24 h of admission and positive (≥2/4) systemic inflammatory response syndrome (SIRS) criteria. Primary exposure was maximum qSOFA score within 48 h of culture collection and primary outcome was mortality at 28 days. Baseline risk of mortality was determined using a multivariable logistic regression model with age, gender, and co-morbidities significantly associated with the outcome. Predictive validity was assessed by discrimination of mortality using area under the receiver operating characteristic (AUROC) curve compared to a model using baseline risk factors alone. Of 253 patients (mean age 54 years (SD 16)) included in the analysis, 23 (9.1%) died by 28 days after enrollment. Of those who died, 0 (0%) had a qSOFA score of 0, 8 (35%) had a score of 1, and 15 (65%) had a score ≥2. The AUROC of qSOFA plus baseline risk was significantly greater than for the baseline risk model alone (AUROC_qSOFA = 0.80 (95% CI, 0.70–0.89), AUROC_baseline = 0.62 (95% CI, 0.49–0.75); p < 0.001). Among adults admitted to four Thai hospitals with community-onset coagulase-positive staphylococcal infection and SIRS, the qSOFA score had good predictive validity for sepsis.

The Specific Organism: Not Bacterial Gram Type: Drives the Inflammatory Response in Septic Shock

BACKGROUND AND HYPOTHESIS

The inflammatory response was targeted by unsuccessful therapies but ignored pathogen. We hypothesized that the inflammatory response differs according to organism in human septic shock.

MATERIALS AND METHODS

We measured 39 cytokines at baseline and 24 h in patients (n = 363) in the Vasopressin and Septic Shock Trial (VASST). We compared cytokine profiles (cytokine functional class) at baseline and at 24 h by organism and used hierarchical clustering to classify cytokines according to 28-day outcomes.

RESULTS

In 363 patients, 88 and 176 patients had at least 1 species isolated from blood and other sites, respectively. Cytokine levels differed significantly according to organism: Neisseria meningitidis and Streptococcus pneumoniae had the highest (baseline and at 24 h), while Enterococcus faecalis (blood) had the lowest mean cytokine levels. N. meningitidis and Klebsiella pneumoniae had significantly higher cytokine levels at baseline versus 24 h (p = 0.01 and 0.02, respectively); E. faecalis had significantly higher cytokine levels at 24 h versus baseline. Hierarchical clustering heat maps showed that pathogens elicited similar cytokine responses not related to the functional cytokine class.

CONCLUSION

The organism type induces different cytokine profiles in septic shock. Specific gram-positive and gram-negative pathogens stimulated similar plasma cytokine-level patterns.

Phagocytosis of live and dead Escherichia coli and Staphylococcus aureus in human whole blood is markedly reduced by combined inhibition of C5aR1 and CD14

BACKGROUND

Sepsis is a dysregulated host response to infection. The aim of this study was to investigate the effects of complement- and CD14 inhibition on phagocytosis of live and dead Gram-negative and Gram-positive bacteria in human whole blood.

METHODS

Lepirudin-anticoagulated blood was incubated with live or dead E. coli or S. aureus at 37 °C for 120 min with or without the C5aR1 antagonist PMX53 and/or anti-CD14. Granulocyte and monocyte phagocytosis were measured by flow cytometry, and five plasma cytokines by multiplex, yielding a total of 28 mediators of inflammation tested for.

RESULTS

16/28 conditions were reduced by PMX53, 7/28 by anti-CD14, and 24/28 by combined PMX53 and CD14 inhibition. The effect of complement inhibition was quantitatively more pronounced, in particular for the responses to S. aureus. The effect of anti-CD14 was modest, except for a marked reduction in INF-β. The responses to live and dead S. aureus were equally inhibited, whereas the responses to live E. coli were inhibited less than those to dead E. coli.

CONCLUSION

C5aR1 inhibited phagocytosis-induced inflammation by live and dead E. coli and S. aureus. CD14 blockade potentiated the effect of C5aR1 blockade, thus attenuating inflammation.

Biomarkers of endothelial activation/dysfunction distinguish sub-groups of Ugandan patients with sepsis and differing mortality risks

BACKGROUND

Sepsis is a complex clinical syndrome with substantial heterogeneity. We sought to identify patterns of serum biomarkers of endothelial activation and dysfunction in individuals with sepsis and evaluate subgroup-specific differences in mortality.

METHODS

Adult patients with sepsis (n=426) were consecutively recruited from two hospitals in Uganda. Clinical information was collected and serum concentrations of eleven biomarkers involved in the endothelial response to infection were measured in samples from 315 patients. Latent variable models were fit to evaluate whether the endothelial response to sepsis consists of one unified biological process or multiple processes and to identify subgroups of patients with distinct host-response profiles. Differences in survival at day 28 were evaluated using Kaplan-Meier survival curves.

RESULTS

We identified three patient subgroups characterized by unique host endothelial response profiles. Patients fitting Profile 2 had significantly worse survival (log-rank p<0.001). Four latent factors (Factor 1-4) were identified, each potentially representing distinct biological processes for the endothelial response to sepsis: Factor 1 (CHI3L1, sTREM1, sFLT1); Factor 2 (ANGPT1, PF4, VEGF); Factor 3 (CXCL10, VWF, sICAM1); and Factor 4 (ANGPT2, sTEK).

CONCLUSION

Patient profiles based on patterns of circulating biomarkers of endothelial responses may provide a clinically meaningful way to categorize patients into homogeneous subgroups and may identify patients with a high risk of mortality. Profile 2 may represent dysfunction of the endothelial response to infection.

FUNDING

Primary funding: Investigator-Initiated Award provided by Pfizer, Inc (WMS, STJ). Additional support: Canadian Institutes of Health Research (CIHR) Foundation grant (KCK; FDN-148439) and the Canada Research Chair program (KCK).

Sepsis Induced by Cecal Ligation and Puncture

Despite advances in intensive care unit interventions, including the use of specific antibiotics and anti-inflammation treatment, sepsis with concomitant multiple organ failure is the most common cause of death in many acute care units. In order to understand the mechanisms of clinical sepsis and develop effective therapeutic modalities, there is a need to use effective experimental models that faithfully replicate what occurs in patients with sepsis. Several models are commonly used to study sepsis, including intravenous endotoxin challenge, injection of live organisms into the peritoneal cavity, establishing abscesses in the extremities, and the induction of experimental polymicrobial peritonitis via cecal ligation and puncture (CLP). Here, we describe the surgical procedure of CLP in mice, which has been demonstrated to closely replicate the nature and course of clinical sepsis in human subjects.

Coronary Lesions and Systemic Inflammatory Response Syndrome in Kawasaki Disease

Introduction:

In patients with Kawasaki disease (KD), who later develop coronary artery lesions (CALs), several inflammatory cytokines are reportedly higher than in patients without CALs. Systemic inflammatory response syndrome (SIRS) is used as a clinical index of hypercytokinemia. The objective of this study was to determine whether SIRS is related to CAL formation.

Methods:

We conducted a retrospective cohort study of KD patients admitted to our hospital between July 2012 and July 2015. The subjects were classified into the SIRS or the non-SIRS group based on their vital signs and blood test results. Their initial treatment was determined by their Kobayashi score. We compared the incidence of CALs between the two groups.

Results:

Of 357 KD patients, 277 were included in this study and 175 (63.2%) met the SIRS criteria. The incidence of CAL formation at week 1 in the clinical course and at one month after the primary treatment was significantly higher in the SIRS group than in the non-SIRS group (17.7% vs. 7.8%, p = 0.03 and 10.9% vs. 3.9%, p = 0.03, respectively). Multivariate analyses showed that after adjusting for each variable of the Kobayashi score, SIRS was an independent risk factor for CAL formation at week 1 in the clinical course (odds ratio, 2.7; 95% confidence interval, 1.03–7.23; p = 0.04).

Conclusions:

SIRS can be a risk factor for CAL in the acute phase of KD.

Management of patients with septic shock due to Candida infection

Septic shock represents a serious complication occurring between 6% and 30% of all hospitalized patients; Candida septic shock represents a challenge for clinicians due to the absence of specific risk factors, diagnostic tests, and management. Identification of specific risk factors and use of biomarkers are useful tools considering that differentiation of Candida from bacterial septic shock is demanding. Early effective antifungal treatment, preferably with echinocandins with an adequate source control, represents the best approach for improving survival of patients with septic shock due to Candida. Given the importance of adequate therapy and source control in septic shock attributable to Candida clinical strategies and pathways are needed. This review will focus on epidemiology of septic shock in patients with invasive candidiasis with special attention to diagnostic pathways and treatment strategies.

Staphylococcus aureus modulation of innate immune responses through Toll-like (TLR), (NOD)-like (NLR) and C-type lectin (CLR) receptors

Early recognition of pathogens by the innate immune system is crucial for bacterial clearance. Many pattern recognition receptors (PRRs) such as Toll-like (TLRs) and (NOD)-like (NLRs) receptors have been implicated in initial sensing of bacterial components. The intracellular signaling cascades triggered by these receptors result in transcriptional upregulation of inflammatory pathways. Although this step is crucial for bacterial elimination, it is also associated with the potential for substantial immunopathology, which underscores the need for tight control of inflammatory responses. The leading human bacterial pathogen Staphylococcus aureus expresses over 100 virulence factors that exert numerous effects upon host cells. In this manner, the pathogen seeks to avoid host recognition or perturb PRR-induced innate immune responses to allow optimal survival in the host. These immune system interactions may result in enhanced bacterial proliferation but also provoke systemic cytokine responses associated with sepsis. This review summarizes recent findings on the various mechanisms applied by S. aureus to modulate or interfere with inflammatory responses through PRRs. Detailed understanding of these complex interactions can provide new insights toward future immune-stimulatory therapeutics against infection or immunomodulatory therapeutics to suppress or correct dysregulated inflammation.

Bioactive nano-metal-organic frameworks as antimicrobials against Gram-positive and Gram-negative bacteria

More effective antibiotics are needed to overcome the problem of multidrug resistance. The antibacterial efficacies of three Zn-based nano metal-organic frameworks (nMOFs) - IRMOF-3, MOF-5, and Zn-BTC - were explored, both alone and as mixtures with ampicillin and kanamycin. When tested against Escherichia coli, Staphylococcus aureus, Staphylococcus lentus, and Listeria monocytogenes, the nMOF/drug mixtures demonstrated synergistic (IRMOF-3/kanamycin) or additive (other nMOF/drug combinations) effects compared with the nMOFs or antibiotics alone. Zn-Based nMOFs can reduce the burden of the new discovery of antimicrobial pharmaceuticals by increasing the potency of existing antibiotics.

Bacteriolysis - a mere laboratory curiosity?

The role of bacteriolysis in the pathophysiology of microbial infections dates back to 1893 when Buchner and Pfeiffer reported for the first time the lysis of bacteria by immune serum and related this phenomenon to the immune response. Later on, basic anti-microbial peptides and certain beta-lactam antibiotics have been shown not only to kill microorganisms but also to induce bacteriolysis and the release of cell-wall components. In 2009, a novel paradigm was offered suggesting that the main cause of death in sepsis is due to the exclusive release from activated human phagocytic neutrophils (PMNs) traps adhering upon endothelial cells of highly toxic nuclear histone. Since activated PMNs also release a plethora of pro-inflammatory agonists, it stands to reason that these may act in synergy with histone to damage cells. Since certain beta lactam antibiotics may induce bacteriolysis, it is questioned whether these may aggravate sepsis patient's condition. Enigmatically, since the term bacteriolysis and its possible involvement in sepsis is hardly ever mentioned in the extensive clinical articles and reviews dealing with critical care, we hereby aim to refresh the concept of bacteriolysis and its possible role in the pathogenesis of post infectious sequelae.

Propranolol Dosing Practices in Adult Burn Patients: Implications for Safety and Efficacy

Studies in children with burn injuries have demonstrated that propranolol improves metabolism and reduces muscle protein wasting. However, safety and efficacy in adults are less well established than in children. The purpose of this study was to determine safety of propranolol use in adult patients with burn injuries. Medical records were reviewed for burn-injured adults receiving propranolol. Patients between 18 and 65 years old and with ≥20% TBSA burn were included. Fifty-four patients met the criteria with mean age of 37 years and mean burn size of 38% TBSA. Propranolol dosages ranged from 0.1 to 3.8 mg/kg/day, with an average maximum dosage of 0.61 mg/kg/day. Mean heart rate decreased by 25% during 4 weeks. Seventy-two percent of patients experienced at least one episode of hypotension and 15% experienced bradycardia. Propranolol doses were most frequently held for low blood pressure; 32% of patients had at least one dose held for hypotension. This retrospective analysis suggests that modest dosing of propranolol results in frequent episodes of hypotension or bradycardia. Our data suggest that adults do not tolerate the higher doses reported in a pediatric population. Despite potential beneficial anti-catabolic effects of propranolol, burn care providers must recognize potential iatrogenic hemodynamic effects of this intervention. Our data support the need for prospective multicenter studies to delineate the safety and efficacy of propranolol in adult burn-injured patients.

MKP-1 negative regulates Staphylococcus aureus induced inflammatory responses in Raw264.7 cells: roles of PKA-MKP-1 pathway and enhanced by rolipram

MAP phosphatases (MKP)-1 acts as an important regulator of innate immune response through a mechanism of control and attention both MAPK and NF-κB molecules during bacterial infection. However, the regulatory role of MKP-1 in the interplay between MAPK and NFκB pathway molecules is still not fully understood. In present study, we showed a direct interactions of p38, ERK or IκBα with MKP-1, and demonstrated that MKP-1 was a pivotal feedback control for both MAP kinases and NF-κB pathway in response to S. aureus. In addition, we found that rolipram had anti-inflammatory activity and repressed IκBα activation induced by S. aureus via PKA-MKP-1 pathway. Our report also demonstrated that PKA-cα can directly bind to IκBα upon S. aureus stimulation, which influenced the downstream signaling of PKA pathway, including altered the expression of MKP-1. These results presented a novel mechanism of PKA and IκB pathway, which may be targeted for treating S. aureus infection.

Gastrointestinal cytomegalovirus disease in a patient with pemphigus vulgaris treated with corticosteroid and mycophenolate mofetil

Pemphigus vulgaris is an autoimmune disease characterized by the formation of suprabasal intra-epidermal blisters on the skin and mucosal surfaces. Infectious diseases are the main cause of death in patients with pemphigus due to the disrupture of the physiological skin barrier, immune dysregulation, and the use of immunosuppressive medications leaving the patient prone to acquire opportunistic infections. We report the case of a 67-year-old woman diagnosed with pemphigus vulgaris, who was irregularly taking prednisone and mycophenolate mofetil. She was hospitalized because of a 1-month history of watery diarrhea and oral ulcers. Unfortunately, the patient died suddenly on the ward. The autopsy revealed a bilateral saddle pulmonary embolism, Gram-positive cocci bronchopneumonia, and gastrointestinal cytomegalovirus infection, causing extensive gastrointestinal mucosal ulcers.

TLR4 genetic variation is associated with inflammatory responses in Gram-positive sepsis

OBJECTIVES

To identify important pathogen recognition receptor (PRR) pathways regulating innate immune responses and outcome in Staphylococcus aureus sepsis.

METHODS

We analysed whether candidate PRR pathway genetic variants were associated with killed S. aureus-induced cytokine responses ex vivo and performed follow-up in vitro studies. We tested the association of our top-ranked variant with cytokine responses and clinical outcomes in a prospective multicentre cohort of patients with staphylococcal sepsis.

RESULTS

An intronic TLR4 polymorphism and expression quantitative trait locus, rs1927907, was highly associated with cytokine release induced by stimulation of blood from healthy Thai subjects with S. aureus ex vivo. S. aureus did not induce TLR4-dependent NF-κB activation in transfected HEK293 cells. In monocytes, tumor necrosis factor (TNF)-α release induced by S. aureus was not blunted by a TLR4/MD-2 neutralizing antibody, but in a monocyte cell line, TNF-α was reduced by knockdown of TLR4. In Thai patients with staphylococcal sepsis, rs1927907 was associated with higher interleukin (IL)-6 and IL-8 levels as well as with respiratory failure. S. aureus-induced responses in blood were most highly correlated with responses to Gram-negative stimulants whole blood.

CONCLUSIONS

A genetic variant in TLR4 is associated with cytokine responses to S. aureus ex vivo and plasma cytokine levels and respiratory failure in staphylococcal sepsis. While S. aureus does not express lipopolysaccharide or activate TLR4 directly, the innate immune response to S. aureus does appear to be modulated by TLR4 and shares significant commonality with that induced by Gram-negative pathogens and lipopolysaccharide.

Structure/function relationships of lipoteichoic acids

The role of lipoteichoic acids (LTAs) from Gram-positive bacteria as immunostimulatory molecules was controversial for many years, as inadequate preparation methods as well as heterogeneous and endotoxin-contaminated commercial preparations led to conflicting results. An improved purification methodology for LTA now yields potent bioactive and chemically defined material, which is currently being characterized in various models. A synthetic analogue of Staphylococcus aureus LTA has proven the structure/function relationship. The key role of D-alanine esters for the immune response of LTA was confirmed by synthetic derivatives. The glycolipid anchor of LTA plays a central role analogous to the lipid A of LPS. Methodological aspects and criteria for quality assessment of LTA preparations are discussed.

Predictors of survival in adults undergoing extracorporeal membrane oxygenation with severe infections

BACKGROUND

To identify novel factors associated with the survival of septic adults receiving extracorporeal membrane oxygenation (ECMO) to improve patient selection and outcomes.

METHODS

Cases were identified from our ECMO registry from 2001 to 2011 if they were ≥16 years and received ECMO for life-threatening sepsis.

RESULTS

A total of 151 adults with a median (25th-75th percentile) age of 51 (37-63) years were analyzed. Pneumonia (50%), myocarditis (20%), and primary bloodstream infections (15%) were the main types of infection, caused by predominantly nonfermentative Gram-negative bacteria (NFGNB) (26%), Enterobacteriaceae (24%), and Gram-positive cocci (21%). The in-hospital mortality of patients with NFGNB, enteric, and Gram-positive bacterial pneumonias were 100%, 68%, and 14%, respectively. Using the Cox-proportional hazards model, we found that age >75 years (hazard ratio [HR], 1.98, 95% confidence interval [95% CI], 1.30-3.02), pre-ECMO dialysis (HR, 3.20, 95% CI, 1.34-7.63), longer door-to-ECMO intervals (HR, 1.01, 95% CI, 1.00-1.02), venoarterial mode (HR, 2.58, 95% CI, 1.55-4.21), and fungal (HR, 2.83, 95% CI, 1.36-5.88) and NFGNB sepsis (HR, 2.48, 95% CI, 1.44-4.27) were associated with mortality. Gram-positive sepsis (HR, 0.20, 95% CI, 0.08-0.57), myocarditis (HR, 0.12, 95% CI, 0.06-0.27), pneumonia (HR, 0.54, 95% CI, 0.30-0.90), and effective empirical antimicrobial therapy were predictive of survival (HR, 0.57, 95% CI, 0.37-0.89); all P < .05. Excluding the 67 heavily premorbid patients, we found that 54% survived ECMO and 42% survived to discharge, with significantly more survivors with door-to-ECMO times of ≤96 hours than >96 hours (59% vs 15%, P < .0001).

CONCLUSIONS

Better outcomes were associated with door-to ECMO times of 96 hours or less, for Gram-positive rather than Gram-negative sepsis, and for pneumonia rather than primary bloodstream infections.

Comparison of sepsis rats induced by caecal ligation puncture or Staphylococcus aureus using a LC-QTOF-MS metabolomics approach

Sepsis is a whole-body inflammatory response to infection with high mortality and is treated in intensive care units (ICUs). In the present study, to identify metabolic biomarkers that can differentiate sepsis models induced by caecal ligation puncture (CLP) or Staphylococcus aureus (S. aureus), small molecular metabolites in the serum were measured by liquid chromatography quadruple time-of-flight mass spectrometry (LC-QTOF-MS) and analysed using the multivariate statistical analysis (MVA) of partial least square-discrimination analysis (PLS-DA) method. The results demonstrated that the body showed obvious metabolic disorders in the sepsis groups compared with the control group. A total of 8 potential biomarkers were identified in the CLP group, and 10 potential biomarkers were identified in the S. aureus group. These potential biomarkers primarily reflected an energy metabolism disorder, inflammatory response, oxidative stress and tissue damage, which occur during sepsis, and these markers might potentially be used to differentiate CLP from Staphylococcus aureus sepsis.

Sepsis Patients with First and Second-Hit Infections Show Different Outcomes Depending on the Causative Organism

Objective: With improving rates of initial survival in severe sepsis, second-hit infections that occur following resolution of the primary insult carry an increasing burden of morbidity. However, despite the clinical relevance of these infections, no data are available on differential outcomes in patients with first and second-hit infections depending on the nature of the causative organism. This study aims to explore any differences in these subgroups.

Design: In a retrospective, observational cohort study, the United Kingdom Intensive Care National Audit & Research Centre (ICNARC) database was used to explore the outcomes of patient with first-hit infections leading to sepsis, and sepsis patients with second-hit infections grouped according to the Gram status of the causative organism.

Setting: General critical care units in England, Wales, and Northern Ireland participating in the ICNARC programme between 1 January, 2007 and 30 June, 2012.

Patients: Patient groups analyzed included 2119 patients with and 1319 patients without sepsis who developed an intensive care unit acquired infection in blood. Subgroups included patients with trauma, emergency neurosurgery, elective surgery, and cardiogenic shock.

Measurements and main results: Gram-negative organisms were associated with poorer outcomes in first-hit infections. The 90-day mortality of patients who developed a Gram-negative infection was 43.6% following elective surgery and 27.9% following trauma. This compared with a mortality of 25.6 and 20.6%, respectively, in Gram-positive infections. Unexpectedly, an inverse relationship between Gram status and mortality was observed in second-hit infections. Patients with an initial diagnosis of sepsis who developed secondary infections caused by Gram-negative organisms had a 90-day mortality of 40.4%, compared with 43.6% in Gram-positive infections.

Conclusions: Our study identifies a fundamental difference in patient outcomes between first-hit and second-hit bacterial infections, which may be due to genetic, microbiological, immunological, and environmental factors. This finding has direct implications for risk stratification and defines future research priorities.

Peptides with dual mode of action: Killing bacteria and preventing endotoxin-induced sepsis

Bacterial infections, with the most severe form being sepsis, can often not be treated adequately leading to high morbidity and lethality of infected patients in critical care units. In particular, the increase in resistant bacterial strains and the lack of new antibiotics are main reasons for the worsening of the current situation, As a new approach, the use of antimicrobial peptides (AMPs) seems to be promising, combining the ability of broad-spectrum bactericidal activity and low potential of induction of resistance. Peptides based on natural defense proteins or polypeptides such as lactoferrin, Limulus anti-lipopolysaccharide factor (LALF), cathelicidins, and granulysins are candidates due to their high affinity to bacteria and to their pathogenicity factors, in first line lipopolysaccharide (LPS, endotoxin) of Gram-negative origin. In this review, we discuss literature with the focus on the use of AMPs from natural sources and their variants as antibacterial as well as anti-endotoxin (anti-inflammatory) drugs. Considerable progress has been made by the design of new AMPs for acting efficiently against the LPS-induced inflammation reaction in vitro as well as in vivo (mouse) models of sepsis. Furthermore, the data indicate that efficient antibacterial compounds are not necessarily equally efficient as anti-endotoxin drugs and vice versa. The most important reason for this may be the different molecular geometry of LPS in bacteria and in free form. This article is part of a Special Issue entitled: Antimicrobial peptides edited by Karl Lohner and Kai Hilpert.

Cytokine profile in severe Gram-positive and Gram-negative abdominal sepsis

Sepsis is a principal cause of death in critical care units worldwide and consumes considerable healthcare resources. The aim of our study was to determine whether the early cytokine profile can discriminate between Gram-positive and Gram-negative bacteraemia (GPB and GNB, respectively) and to assess the prognostic value regarding outcome in critically ill patients with severe abdominal sepsis. The outcome measure was hospital mortality. Blood samples were obtained from 165 adult patients with confirmed severe abdominal sepsis. Levels of the proinflammatory mediators TNF-α, IL-8, IL-12 and IFN-γ and the anti-inflammatory mediators IL-1ra, IL-4, IL-10 and TGF-β1 were determined and correlated with the nature of the bacteria isolated from the blood culture and outcome. The cytokine profile in our study indicated that the TNF-α levels were 2-fold, IL-8 were 3.3-fold, IFN-γ were 13-fold, IL-1ra were 1.05-fold, IL-4 were 1.4-fold and IL-10 were 1.83-fold higher in the GNB group compared with the GPB group. The TNF-α levels were 4.7-fold, IL-8 were 4.6-fold, IL-1ra were 1.5-fold and IL-10 were 3.3-fold higher in the non-survivors compared with the survivors.

Sepsis pathophysiology and anesthetic consideration

Sepsis remains to be a significant health care issue associated with high mortality and healthcare cost, despite the extensive effort to better understand the pathophysiology of the sepsis. Recently updated clinical guideline for severe sepsis and septic shock, "Surviving Sepsis Campaign 2012", emphasizes the importance of early goal-directed therapy, which can be implemented in intraoperative management of sepsis patients. Herein, we review the updates of current guideline and discuss its application to anesthesic management. Furthermore, we review the recent advance in knowledge of sepsis pathophysiology, focusing on immune modulation, which may lead to new clinical therapeutic approach to sepsis.

Prior statin use and 90-day mortality in Gram-negative and Gram-positive bloodstream infection: a prospective observational study

In several studies on patients with bloodstream infection (BSI), prior use of statins has been associated with improved survival. Gram-positive and Gram-negative bacteria alert the innate immune system in different ways. We, therefore, studied whether the relation between prior statin use and 90-day total mortality differed between Gram-positive and Gram-negative BSI. We conducted a prospective observational cohort study of 1,408 adults with BSI admitted to Levanger Hospital between January 1, 2002, and December 31, 2011. Data on the use of statins and other medications at admission, comorbidities, functional status, treatment, and outcome were obtained from the patients’ hospital records. The relation of statin use with 90-day mortality differed between Gram-negative and Gram-positive BSI (p-value for interaction 0.01). Among patients with Gram-negative BSI, statin users had significantly lower 90-day total mortality [odds ratio (OR) 0.42, 95 % confidence interval (CI) 0.23–0.75, p = 0.003]. The association remained essentially unchanged after adjusting for the effect of sex, age, functional status before the infection, and underlying diseases that were considered confounders (adjusted OR 0.38, 95 % CI 0.20–0.72, p = 0.003). A similar analysis of patients with Gram-positive BSI showed no association of statin use with mortality (adjusted OR 1.22, 95 % CI 0.69–2.17, p = 0.49). The present study suggests that prior statin use is associated with a lower 90-day total mortality in Gram-negative BSI, but not in Gram-positive BSI.

Non-pulmonary infections but not specific pathogens are associated with increased risk of AKI in septic shock

INTRODUCTION

Little is known regarding the relationship between the anatomic infection site and etiologic pathogen with the occurrence of acute kidney injury (AKI) in severe infections. We set out to determine the association between the site of infection, type of pathogen in septic shock and occurrence of AKI.

METHODS

Using a large, international multicenter database that included data from 28 academic and community hospitals, we retrospectively analyzed adult (age >18 years) cases of septic shock occurring between January 1996 and December 2008. Early acute kidney injury (AKI) was classified by the RIFLE criteria at or within 24 h of shock diagnosis. Multivariate logistic regression was used to determine the association between the infection site/microbial pathogen and occurrence of AKI. Analyses were adjusted for demographics, illness severity, comorbidities and intensive care unit interventions (partial adjustment) ± site of infection and microbial pathogen (full adjustment).

RESULTS

After exclusions, 4,493 cases from potentially eligible patients in the database were included in the analytic cohort of whom 3,298 (73.4 %) experienced AKI. Patients with AKI were older (p < 0.0001), had a higher mean Acute Physiology and Chronic Health Evaluation score (p < 0.0001), and had greater laboratory and hemodynamic abnormalities. The most common site of infection among septic shock patients with AKI was the lung (34.5 %), followed by gastrointestinal (GI) (26.2 %) and urinary (15.3 %) sources. Likewise, the most common infecting organism among septic shock patients with AKI was E. coli (23.9 %) followed by S. aureus (GI) (16.1 %) and other enterobacteriaceae (15.7 %). There was a large degree of variability in the occurrence of AKI based on the site of infection and the pathogen in unadjusted analysis (p < 0.0001), which persisted with partial (excluding infection site and microbial pathogen grouping) adjustment (p < 0.0001). Fully adjusted multivariate analysis showed significant variations in AKI only in relation to the anatomic source of infection, with non-pulmonary infections having higher risk than pulmonary infections. The pathogen group/pathogen had no significant independent impact on AKI.

CONCLUSION

This study demonstrates that the presence of septic AKI varies significantly based on the site of infection but not the type of causative organism.

The EUPHRATES trial (Evaluating the Use of Polymyxin B Hemoperfusion in a Randomized controlled trial of Adults Treated for Endotoxemia and Septic shock): study protocol for a randomized controlled trial

Background

Septic shock is common and has unacceptably high morbidity, mortality, and associated cost with numerous failed attempts at developing effective therapies. Endotoxin, one of the most potent mediators of sepsis, is found in high levels in approximately 50% of patients with septic shock. Polymyxin B (PMX) hemoperfusion has been shown in numerous studies to successfully remove endotoxin and potentially improve outcomes. EUPHRATES (Evaluating the Use of Polymyxin B Hemoperfusion in a Randomized controlled trial of Adults Treated for Endotoxemia and Septic shock) is a theragnostic trial (matching blood measurement to treatment capability) of PMX hemoperfusion in patients with septic shock and confirmed endotoxemia as measured by the endotoxin activity assay (EAA).

Methods

EUPHRATES is a pivotal regulatory trial that is multi-centered, placebo-controlled and blinded. The trial is being conducted in fifty ICUs in the United States and Canada and is powered to enroll 360 patients. Patients with persistent septic shock despite adequate fluid resuscitation on vasopressors for more than 2 and less than 30 hours are eligible for measurement of the EAA. Those with EAA ≥0.60 are eligible to be randomized to treatment with two sessions of PMX hemoperfusion 24 hours apart. The primary endpoint for the trial is 28-day all-cause mortality.

Discussion

Unique features of the trial include absence of systemic inflammatory response (SIRS) criteria as a requirement for inclusion, use of the EAA to confirm endotoxemia as a requisite for treatment, and use of a detailed “façade” hemoperfusion event as a blinding mechanism. The outcomes of the second interim analysis included a resizing of the trial to 650 patients and the addition of an exclusion criterion of subjects with multiple organ dysfunction score (MODS) ≤ 9. Results are anticipated in 2016.

Trial registration

Clinicaltrials.gov identifier: NCT01046669. Registered: January 8, 2010.

Polymyxin B hemoperfusion: a mechanistic perspective

Direct hemoperfusion therapy with polymyxin B immobilized fiber cartridge (PMX-DHP) is an established strategy in the treatment of septic shock in Japan and parts of Western Europe. PMX-DHP is currently the subject of a pivotal North American randomized controlled trial (EUPHRATES) in patients with septic shock and confirmed endotoxemia, as measured by the endotoxin activity assay. The major mechanism of action of this therapy is the removal of circulating endotoxin. High affinity binding of circulating endotoxin by the PMX-DHP column may decrease circulating endotoxin levels by up to 90% after two standard treatments. Basic research has shown reductions in circulating cytokine levels and in renal tubular apoptosis. Clinical research has shown that PMX-DHP therapy results in hemodynamic improvements, improvements in oxygenation, renal function, and reductions in mortality. Further research is needed to further define additional patient populations with endotoxemia that may benefit from PMX-DHP therapy as well as to further elucidate dosing, timing, and additional information on mechanisms of action. This review will present the mechanistic rationale for this targeted strategy of endotoxin removal using PMX-DHP in endotoxemic septic patients, highlighting both the specific effects of the therapy and the evidence accumulated so far of clinical improvement following this therapy in terms of recovery of organ function.

Combined inhibition of complement and CD14 efficiently attenuated the inflammatory response induced by Staphylococcus aureus in a human whole blood model

The complement and TLR systems are activated in sepsis, contributing to an unfavorable inflammatory "storm." Combined inhibition of these systems has been documented to efficiently attenuate the inflammatory responses induced by Gram-negative bacteria. In this study, we hypothesized that the combined inhibition would attenuate the inflammatory responses induced by Gram-positive bacteria. Staphylococcus aureus bacteria (strains Cowan and Wood), as well as S. aureus cell wall lipoteichoic acid (LTA), were incubated in thrombin-inhibited human whole blood. Complement was inhibited at the level of C3 and C5, and the TLRs by inhibiting CD14 and TLR2. Thirty-four inflammatory markers were measured by multiplex technology and flow cytometry. Thirteen markers increased significantly in response to Cowan and Wood, and 12 in response to LTA. Combined inhibition with the C3 inhibitor compstatin and the anti-CD14 Ab 18D11 significantly reduced 92 (Cowan, LTA) and 85% (Wood) of these markers. Compstatin alone significantly reduced 54 (Cowan), 38 (Wood), and 83% (LTA), whereas anti-CD14 alone significantly reduced 23, 15, and 67%, respectively. Further experiments showed that the effects of complement inhibition were mainly due to inhibition of C5a interaction with the C5a receptor. The effects on inhibiting CD14 and TLR2 were similar. The combined regimen was more efficient toward the bacterial effects than either complement or anti-CD14 inhibition alone. Complement was responsible for activation of and phagocytosis by both granulocytes and monocytes. Disrupting upstream recognition by inhibiting complement and CD14 efficiently attenuated S. aureus-induced inflammation and might be a promising treatment in both Gram-negative and Gram-positive sepsis.

Healthcare disparities in critical illness

OBJECTIVE

To summarize the current literature on racial and gender disparities in critical care and the mechanisms underlying these disparities in the course of acute critical illness.

DATA SOURCES

MEDLINE search on the published literature addressing racial, ethnic, or gender disparities in acute critical illness, such as sepsis, acute lung injury, pneumonia, venous thromboembolism, and cardiac arrest.

STUDY SELECTION

Clinical studies that evaluated general critically ill patient populations in the United States as well as specific critical care conditions were reviewed with a focus on studies evaluating factors and contributors to health disparities.

DATA EXTRACTION

Study findings are presented according to their association with the prevalence, clinical presentation, management, and outcomes in acute critical illness.

DATA SYNTHESIS

This review presents potential contributors for racial and gender disparities related to genetic susceptibility, comorbidities, preventive health services, socioeconomic factors, cultural differences, and access to care. The data are organized along the course of acute critical illness.

CONCLUSIONS

The literature to date shows that disparities in critical care are most likely multifactorial involving individual, community, and hospital-level factors at several points in the continuum of acute critical illness. The data presented identify potential targets as interventions to reduce disparities in critical care and future avenues for research.

Definitions and pathophysiology of sepsis

Mortality rates for sepsis and septic shock have not improved in the past decade. The Surviving Sepsis Campaign (SSC) guidelines released in 2012 emphasize early recognition and treatment of sepsis, in an effort to reduce the burden of sepsis worldwide. This series of review articles will discuss the pathophysiology of sepsis; comorbidities, such as multiorgan dysfunction syndrome (MODS), acute respiratory distress syndrome (ARDS), and endocrine issues; and finally, management of sepsis and septic shock.

The crystal structure of human soluble CD14 reveals a bent solenoid with a hydrophobic amino-terminal pocket

Human monocyte differentiation Ag CD14 is a pattern recognition receptor that enhances innate immune responses to infection by sensitizing host cells to bacterial LPS (endotoxin), lipoproteins, lipoteichoic acid, and other acylated microbial products. CD14 physically delivers these lipidated microbial products to various TLR signaling complexes that subsequently induce intracellular proinflammatory signaling cascades upon ligand binding. The ensuing cellular responses are usually protective to the host but can also result in host fatality through sepsis. In this work, we have determined the x-ray crystal structure of human CD14. The structure reveals a bent solenoid typical of leucine-rich repeat proteins with an amino-terminal pocket that presumably binds acylated ligands including LPS. Comparison of human and mouse CD14 structures shows great similarity in overall protein fold. However, compared with mouse CD14, human CD14 contains an expanded pocket and alternative rim residues that are likely to be important for LPS binding and cell activation. The x-ray crystal structure of human CD14 presented in this article may foster additional ligand-bound structural studies, virtual docking studies, and drug design efforts to mitigate LPS-induced sepsis and other inflammatory diseases.

Sepsis induced by cecal ligation and puncture

Despite advances in intensive care unit interventions, including the use of specific antibiotics and anti-inflammation treatment, sepsis with concomitant multiple organ failure is the most common cause of death in many acute care units. In order to understand the mechanisms of clinical sepsis and develop effective therapeutic modalities, there is a need to use effective experimental models that faithfully replicate what occurs in patients with sepsis. Several models are commonly used to study sepsis, including intravenous endotoxin challenge, injection of live organisms into the peritoneal cavity, establishing abscesses in the extremities, and the induction of polymicrobial peritonitis via cecal ligation and puncture (CLP). Here, we describe the surgery procedure of CLP in mice, which has been proposed to closely replicate the nature and course of clinical sepsis in humans.

Inflammatory cytokine measurement quickly discriminates gram-negative from gram-positive bacteremia in pediatric hematology/oncology patients with septic shock

PURPOSE

We performed a prospective study to evaluate the ability of inflammatory cytokines in discriminating gram-negative from gram-positive bacteremia in septic shock.

METHODS

During the study period, the serum inflammatory cytokine levels were measured at the onset of septic shock by flow cytometry in pediatric hematology/oncology patients with septic shock.

RESULTS

One hundred episodes of septic shock were enrolled. Of 97 episodes of monomicrobial infection, 73.2 % were caused by gram-negative bacteremia and 26.8 % by gram-positive bacteremia. Interleukin (IL)-6, IL-10, and tumor necrosis factor (TNF)-α were closely related to the pediatric index of mortality 2 (PIM2) score and mortality. However, although the PIM2 score and mortality were comparable, the IL-6, IL-10, and TNF-α levels were significantly higher in patients with gram-negative bacteremia (GNB) than those with gram-positive bacteremia (median levels, pg/mL: IL-6: 784.1 vs. 254.4, P = 0.001; IL-10: 192.2 vs. 19.7, P < 0.001; TNF-α: 4.2 vs. 2.0, P < 0.001). Of the three cytokines, IL-10 was the most useful biomarker for GNB prediction in the derivation cohort and a cutoff value of 50 pg/mL showed a sensitivity of 70.8 % and a specificity of 80.0 %, with a positive predictive value of 89.5 %. When this cutoff value was applied to the validation cohort, the sensitivity, specificity, and positive predictive value were 80.9, 75.0, and 90.5 %, respectively.

CONCLUSIONS

Flow cytometry-based inflammatory cytokine measurement is a helpful adjuvant approach for early and quick discrimination of gram-negative from gram-positive bacteremia in pediatric hematology/oncology patients with septic shock which might be useful for evaluating the severity of shock and the selection and/or timely withdrawal or switch of antibiotics.

Inhibitory receptor paired Ig-like receptor B is exploited by Staphylococcus aureus for virulence

The innate immune system has developed to acquire a wide variety of pattern-recognition receptors (PRRs) to identify potential pathogens, whereas pathogens have also developed to escape host innate immune responses. ITIM-bearing receptors are attractive targets for pathogens to attenuate immune responses against them; however, the in vivo role of the inhibitory PRRs in host-bacteria interactions remains unknown. We demonstrate in this article that Staphylococcus aureus, a major Gram-positive bacteria, exploits inhibitory PRR paired Ig-like receptor (PIR)-B on macrophages to suppress ERK1/2 and inflammasome activation, and subsequent IL-6 and IL-1β secretion. Consequently, Pirb(-/-) mice infected with S. aureus showed enhanced inflammation and more effective bacterial clearance, resulting in resistance to the sepsis. Screening of S. aureus mutants identified lipoteichoic acid (LTA) as an essential bacterial cell wall component required for binding to PIR-B and modulating inflammatory responses. In vivo, however, an LTA-deficient S. aureus mutant was highly virulent and poorly recognized by macrophages in both wild-type and Pirb(-/-) mice, demonstrating that LTA recognition by PRRs other than PIR-B mediates effective bacterial elimination. These results provide direct evidence that bacteria exploit the inhibitory receptor for virulence, and host immune system counterbalances the infection.

The enhanced permeability retention effect: a new paradigm for drug targeting in infection

Multidrug-resistant, Gram-negative infection is a major global determinant of morbidity, mortality and cost of care. The advent of nanomedicine has enabled tailored engineering of macromolecular constructs, permitting increasingly selective targeting, alteration of volume of distribution and activity/toxicity. Macromolecules tend to passively and preferentially accumulate at sites of enhanced vascular permeability and are then retained. This enhanced permeability and retention (EPR) effect, whilst recognized as a major breakthrough in anti-tumoral targeting, has not yet been fully exploited in infection. Shared pathophysiological pathways in both cancer and infection are evident and a number of novel nanomedicines have shown promise in selective, passive, size-mediated targeting to infection. This review describes the similarities and parallels in pathophysiological pathways at molecular, cellular and circulatory levels between inflammation/infection and cancer therapy, where use of this principle has been established.