The role of the gut microbiota in sepsis. Lancet Gastroenterol Hepatol. 2017;2:135-143. [PMID: 28403983 DOI: 10.1016/s2468-1253(16)30119-4]

Sepsis roadmap: What we know, what we learned, and where we are going

Sepsis is a life-threatening condition originating as a result of systemic blood infection causing, one or more organ damage due to the dysregulation of the immune response. In 2017, the world health organization (WHO) declared sepsis as a disease of global health priority, needing special attention due to its high prevalence and mortality around the world. Most of the therapeutics targeting sepsis have failed in the clinics. The present review highlights the history of the sepsis, its immunopathogenesis, and lessons learned after the failure of previously used immune-based therapies. The subsequent section, where to go describes in details the importance of the complement system (CS), autophagy, inflammasomes, and microbiota along with their targeting to manage sepsis. These systems are interconnected to each other, thus targeting one may affect the other. We are in an urgent need for a multi-targeting therapeutic approach for sepsis.

Lactobacillus rhamnosus GG Ameliorates Liver Injury and Hypoxic Hepatitis in Rat Model of CLP-Induced Sepsis

BACKGROUND

Probiotic use to prevent gastrointestinal infections in critical care has shown great promise in recent clinical trials. Although well-documented benefits of probiotic use in intestinal disorders, the potential for probiotic treatment to ameliorate liver injury and hypoxic hepatitis following sepsis has not been well explored.

METHODS

In order to evaluate, if Lactobacillus rhamnosus GG (LGG) treatment in septic rats will protect against liver injury, this study used 20-22-week-old Sprague-Dawley rats which were subjected to cecal ligation and puncture to establish sepsis model and examine mRNA and protein levels of IL-1β, NLRP3, IL-6, TNF-a, VEGF, MCP1, NF-kB and HIF-1α in the liver via real-time PCR, Elisa and Western blot.

RESULTS

This study showed that LGG treatment significantly ameliorated liver injury following experimental infection and sepsis. Liver mRNA and protein levels of IL-1β, NLRP3, IL-6, TNF-a, VEGF, MCP1, NF-kB and HIF-1α were significantly reduced in rats receiving LGG.

CONCLUSIONS

Thus, our study demonstrated that LGG treatment can reduce liver injury following experimental infection and sepsis and is associated with improved hypoxic hepatitis. Probiotic therapy may be a promising intervention to ameliorate clinical liver injury and hypoxic hepatitis following systemic infection and sepsis.

Association Between Gut Bacterial Diversity and Mortality in Septic Shock Patients: A Cohort Study

Background

Gut bacterial diversity is decreased in a proportion of patients with septic shock. We attempted to validate the hypothesis that low bacterial diversity increases the risk of mortality.

Material/Methods

All patients with septic shock seen at 2 medical center from 2016 through 2019 were included in this cohort study. Total DNA was isolated from stool, and high-throughput sequencing was performed. Clinical data were extracted from patient medical records and hospital databases. Patients were grouped by gut microbiota bacterial diversity (measured by Shannon diversity index) on presentation. We used logistic regression analysis to evaluate the risk of 28-day mortality in septic patients with low Shannon diversity index.

Results

Of the 150 patients enrolled in this study, low bacterial diversity (Shannon index <3.0) was found in 80 patients and normal diversity (Shannon index ≥3.0) was found in 70 patients. Low diversity was associated with a higher unadjusted mortality risk, compared to those with normal diversity (odds ratio [OR] 2.04, 95% confidence interval [CI] 1.35–2.83). However, this result became non-significant after adjusting the confounding factors such as age, sex, severity of disease, comorbid status, usage of probiotics, enteral nutrition, and antimicrobial drugs (OR 1.93, 95% CI 0.55–2.69).

Conclusions

Our study does not support that low gut bacterial diversity is an independent risk factor for mortality in intensive care unit patients with septic shock.

Mechanisms and treatment of organ failure in sepsis

Sepsis is a dysregulated immune response to an infection that leads to organ dysfunction. Knowledge of the pathophysiology of organ failure in sepsis is crucial for optimizing the management and treatment of patients and for the development of potential new therapies. In clinical practice, six major organ systems - the cardiovascular (including the microcirculation), respiratory, renal, neurological, haematological and hepatic systems - can be assessed and monitored, whereas others, such as the gut, are less accessible. Over the past 2 decades, considerable amounts of new data have helped improve our understanding of sepsis pathophysiology, including the regulation of inflammatory pathways and the role played by immune suppression during sepsis. The effects of impaired cellular function, including mitochondrial dysfunction and altered cell death mechanisms, on the development of organ dysfunction are also being unravelled. Insights have been gained into interactions between key organs (such as the kidneys and the gut) and organ-organ crosstalk during sepsis. The important role of the microcirculation in sepsis is increasingly apparent, and new techniques have been developed that make it possible to visualize the microcirculation at the bedside, although these techniques are only research tools at present.

The microbiome: implications for perioperative and critical care

PURPOSE OF REVIEW

The host-microbiota relationship is integral in human health and can be rapidly disrupted in ways that may contribute to poor recovery from surgery or acute illness. We review key studies by organ system to understand the effect of perioperative and critical illness stress on the microbiota. Throughout the review, our focus is on potential interventions that may be mediated by the microbiome.

RECENT FINDINGS

Although any perioperative intervention can have a profound impact on the gut microbiota, it is less clear how such changes translate into altered health outcomes. Preoperative stress (anxiety, lack of sleep, fasting), intraoperative stress (surgery itself, volatile anesthetics, perioperative antibiotics, blood transfusions), and postoperative stress (sepsis, surgical site infections, acute respiratory distress syndrome, catecholamines, antibiotics, opioids, proton pump inhibitors) have all been associated with alterations of the commensal microflora. These factors (e.g. administration of antibiotics or opioids) can create a favorable environment for emergence of pathogen virulence and development of serious infections and multiorgan failure. Data to recommend therapies aimed at restoring a disrupted microbiota, such as probiotics/prebiotics and fecal microbiota transplants is currently scarce.

SUMMARY

The microbiome is likely to play an important role in the perioperative and ICU setting but existing data is largely descriptive. There is an expanding number of mechanistic studies that attempt to disentangle the complicated bi-directional relationship between the host and the resident microbiota. When these results are combined with ongoing clinical studies, we should be able to offer better therapies aimed at restoring the microbiota in the future.

Enteric dysbiosis is associated with sepsis in patients

Sepsis is defined as a life-threatening organ dysfunction caused by a dysregulated host response to microbial infection. For decades, the potential role of gut microbiota in sepsis pathogenesis has been revealed. However, the systemic and functional link between gut microbiota and sepsis has remained unexplored. To address this gap in knowledge, we carried out systematic analyses on clinical stool samples from patients with sepsis, including 16S rDNA sequencing, metabolomics, and metaproteomics analyses. In addition, we performed fecal microbiota transplantation from human to mice to validate the roles of gut microbiota on sepsis progression. We found that the composition of gut microbiota was significantly disrupted in patients with sepsis compared with healthy individuals. Besides, the microbial functions were significantly altered in septic feces as identified by metabolomics and metaproteomics analyses. Interestingly, mice that received septic feces exhibited more severe hepatic inflammation and injury than mice that received healthy feces after cecal ligation and puncture. Finally, several strains of intestinal microbiota and microbial metabolites were corelated with serum total bilirubin levels in patients with sepsis. Taken together, our data indicated that sepsis development is associated with the disruption of gut microbiota at both compositional and functional levels, and such enteric dysbiosis could promote organ inflammation and injury during sepsis.-Liu, Z., Li, N., Fang, H., Chen, X., Guo, Y., Gong, S., Niu, M., Zhou, H., Jiang, Y., Chang, P., Chen, P. Enteric dysbiosis is associated with sepsis in patients.

Infectious Threats, the Intestinal Barrier, and Its Trojan Horse: Dysbiosis

The ecosystem of the gut microbiota consists of diverse intestinal species with multiple metabolic and immunologic activities and it is closely connected with the intestinal epithelia and mucosal immune response, with which it builds a complex barrier against intestinal pathogenic bacteria. The microbiota ensures the integrity of the gut barrier through multiple mechanisms, either by releasing antibacterial molecules (bacteriocins) and anti-inflammatory short-chain fatty acids or by activating essential cell receptors for the immune response. Experimental studies have confirmed the role of the intestinal microbiota in the epigenetic modulation of the gut barrier through posttranslational histone modifications and regulatory mechanisms induced by epithelial miRNA in the epithelial lumen. Any quantitative or functional changes of the intestinal microbiota, referred to as dysbiosis, alter the immune response, decrease epithelial permeability and destabilize intestinal homeostasis. Consequently, the overgrowth of pathobionts (Staphylococcus, Pseudomonas, and Escherichia coli) favors intestinal translocations with Gram negative bacteria or their endotoxins and could trigger sepsis, septic shock, secondary peritonitis, or various intestinal infections. Intestinal infections also induce epithelial lesions and perpetuate the risk of bacterial translocation and dysbiosis through epithelial ischemia and pro-inflammatory cytokines. Furthermore, the decline of protective anaerobic bacteria (Bifidobacterium and Lactobacillus) and inadequate release of immune modulators (such as butyrate) affects the release of antimicrobial peptides, de-represses microbial virulence factors and alters the innate immune response. As a result, intestinal germs modulate liver pathology and represent a common etiology of infections in HIV immunosuppressed patients. Antibiotic and antiretroviral treatments also promote intestinal dysbiosis, followed by the selection of resistant germs which could later become a source of infections. The current article addresses the strong correlations between the intestinal barrier and the microbiota and discusses the role of dysbiosis in destabilizing the intestinal barrier and promoting infectious diseases.

Microbiota-Immune Interaction in the Pathogenesis of Gut-Derived Infection

Gut-derived infection is among the most common complications in patients who underwent severe trauma, serious burn, major surgery, hemorrhagic shock or severe acute pancreatitis (SAP). It could cause sepsis and multiple organ dysfunction syndrome (MODS), which are regarded as a leading cause of mortality in these cases. Gut-derived infection is commonly caused by pathological translocation of intestinal bacteria or endotoxins, resulting from the dysfunction of the gut barrier. In the last decades, the studies regarding to the pathogenesis of gut-derived infection mainly focused on the breakdown of intestinal epithelial tight junction and increased permeability. Limited information is available on the roles of intestinal microbial barrier in the development of gut-derived infection. Recently, advances of next-generation DNA sequencing techniques and its utilization has revolutionized the gut microecology, leading to novel views into the composition of the intestinal microbiota and its connections with multiple diseases. Here, we reviewed the recent progress in the research field of intestinal barrier disruption and gut-derived infection, mainly through the perspectives of the dysbiosis of intestinal microbiota and its interaction with intestinal mucosal immune cells. This review presents novel insights into how the gut microbiota collaborates with mucosal immune cells to involve the development of pathological bacterial translocation. The data might have important implication to better understand the mechanism underlying pathological bacterial translocation, contributing us to develop new strategies for prevention and treatment of gut-derived sepsis.

Metabolomics Coupled with Transcriptomics Approach Deciphering Age Relevance in Sepsis

Sepsis is a severe disease frequently occurred in the Intenisive Care Unit (ICU), which has a very high morbidity and mortality, especially in patients aged over 65 years. Owing to the aging effect and the ensuing deterioration of body function, the elder patients may have atypical responses to sepsis. Diagnosis and pathogenesis of sepsis in this population are thus difficult, which hindered effective treatment and management in clinic. To investigated age effects on sepsis, 158 elderly septic patients and 71 non-septic elderly participants were enrolled, and their plasma samples were collected for transcriptomics (RNA-seq) and metabolomics (NMR and GC-MS) analyses, which are both increasingly being utilized to discover key molecular changes and potential biomarkers for various diseases. Protein-protein interaction (PPI) analysis was subsequently performed to assist cross-platform integration. Real time polymerase chain reaction (RT-PCR) was used for validation of RNA-seq results. For further understanding of the mechanisms, cecal ligation and puncture (CLP) experiment was performed both in young and middle-aged rats, which were subjected to NMR-based metabolomics study and validated for several key inflammation pathways by western blot. Comprehensive analysis of data from the two omics approaches provides a systematic perspective on dysregulated pathways that could facilitate the development of therapy and biomarkers for elderly sepsis. Additionally, the metabolites of lactate, arginine, histamine, tyrosine, glutamate and glucose were shown to be highly specific and sensitive in distinguishing septic patients from healthy controls. Significant increases of arginine, trimethylamine N-oxide and allantoin characterized elderly patient incurred sepsis. Further analytical and biological validations in different subpopulations of septic patients should be carried out, allowing accurate diagnostics and precise treatment of sepsis in clinic.

Mice Fed an Obesogenic Western Diet, Administered Antibiotics, and Subjected to a Sterile Surgical Procedure Develop Lethal Septicemia with Multidrug-Resistant Pathobionts

Despite antibiotics and sterile technique, postoperative infections remain a real and present danger to patients. Recent estimates suggest that 50% of the pathogens associated with postoperative infections have become resistant to the standard antibiotics used for prophylaxis. Risk factors identified in such cases include obesity and antibiotic exposure. To study the combined effect of obesity and antibiotic exposure on postoperative infection, mice were allowed to gain weight on an obesogenic Western-type diet (WD), administered antibiotics and then subjected to an otherwise recoverable sterile surgical injury (30% hepatectomy). The feeding of a WD alone resulted in a major imbalance of the cecal microbiota characterized by a decrease in diversity, loss of Bacteroidetes, a bloom in Proteobacteria, and the emergence of antibiotic-resistant organisms among the cecal microbiota. When WD-fed mice were administered antibiotics and subjected to 30% liver resection, lethal sepsis, characterized by multiple-organ damage, developed. Notable was the emergence and systemic dissemination of multidrug-resistant (MDR) pathobionts, including carbapenem-resistant, extended-spectrum β-lactamase-producing Serratia marcescens, which expressed a virulent and immunosuppressive phenotype. Analysis of the distribution of exact sequence variants belonging to the genus Serratia suggested that these strains originated from the cecal mucosa. No mortality or MDR pathogens were observed in identically treated mice fed a standard chow diet. Taken together, these results suggest that consumption of a Western diet and exposure to certain antibiotics may predispose to life-threating postoperative infection associated with MDR organisms present among the gut microbiota.IMPORTANCE Obesity remains a prevalent and independent risk factor for life-threatening infection following major surgery. Here, we demonstrate that when mice are fed an obesogenic Western diet (WD), they become susceptible to lethal sepsis with multiple organ damage after exposure to antibiotics and an otherwise-recoverable surgical injury. Analysis of the gut microbiota in this model demonstrates that WD alone leads to loss of Bacteroidetes, a bloom of Proteobacteria, and evidence of antibiotic resistance development even before antibiotics are administered. After antibiotics and surgery, lethal sepsis with organ damage developed in in mice fed a WD with the appearance of multidrug-resistant pathogens in the liver, spleen, and blood. The importance of these findings lies in exposing how the selective pressures of diet, antibiotic exposure, and surgical injury can converge on the microbiome, resulting in lethal sepsis and organ damage without the introduction of an exogenous pathogen.

The intestinal barrier in multiple sclerosis: implications for pathophysiology and therapeutics

Biological barriers are essential for the maintenance of homeostasis in health and disease. Breakdown of the intestinal barrier is an essential aspect of the pathophysiology of gastrointestinal inflammatory diseases, such as inflammatory bowel disease. A wealth of recent studies has shown that the intestinal microbiome, part of the brain-gut axis, could play a role in the pathophysiology of multiple sclerosis. However, an essential component of this axis, the intestinal barrier, has received much less attention. In this review, we describe the intestinal barrier as the physical and functional zone of interaction between the luminal microbiome and the host. Besides its essential role in the regulation of homeostatic processes, the intestinal barrier contains the gut mucosal immune system, a guardian of the integrity of the intestinal tract and the whole organism. Gastrointestinal disorders with intestinal barrier breakdown show evidence of CNS demyelination, and content of the intestinal microbiome entering into the circulation can impact the functions of CNS microglia. We highlight currently available studies suggesting that there is intestinal barrier dysfunction in multiple sclerosis. Finally, we address the mechanisms by which commonly used disease-modifying drugs in multiple sclerosis could alter the intestinal barrier and the microbiome, and we discuss the potential of barrier-stabilizing strategies, including probiotics and stabilization of tight junctions, as novel therapeutic avenues in multiple sclerosis.

Platelets in Sepsis: An Update on Experimental Models and Clinical Data

Beyond their important role in hemostasis, platelets play a crucial role in inflammatory diseases. This becomes apparent during sepsis, where platelet count and activation correlate with disease outcome and survival. Sepsis is caused by a dysregulated host response to infection, leading to organ dysfunction, permanent disabilities, or death. During sepsis, tissue injury results from the concomitant uncontrolled activation of the complement, coagulation, and inflammatory systems as well as platelet dysfunction. The balance between the systemic inflammatory response syndrome (SIRS) and the compensatory anti-inflammatory response (CARS) regulates sepsis outcome. Persistent thrombocytopenia is considered as an independent risk factor of mortality in sepsis, although it is still unclear whether the drop in platelet count is the cause or the consequence of sepsis severity. The role of platelets in sepsis development and progression was addressed in different experimental in vivo models, particularly in mice, that represent various aspects of human sepsis. The immunomodulatory function of platelets depends on the experimental model, time, and type of infection. Understanding the molecular mechanism of platelet regulation in inflammation could bring us one step closer to understand this important aspect of primary hemostasis which drives thrombotic as well as bleeding complications in patients with sterile and infectious inflammation. In this review, we summarize the current understanding of the contribution of platelets to sepsis severity and outcome. We highlight the differences between platelet receptors in mice and humans and discuss the potential and limitations of animal models to study platelet-related functions in sepsis.

Challenge to the Intestinal Mucosa During Sepsis

Sepsis is a complex of life-threating organ dysfunction in critically ill patients, with a primary infectious cause or through secondary infection of damaged tissues. The systemic consequences of sepsis have been intensively examined and evidences of local alterations and repercussions in the intestinal mucosal compartment is gradually defining gut-associated changes during sepsis. In the present review, we focus on sepsis-induced dysfunction of the intestinal barrier, consisting of an increased permeability of the epithelial lining, which may facilitate bacterial translocation. We discuss disturbances in intestinal vascular tonus and perfusion and coagulopathies with respect to their proposed underlying molecular mechanisms. The consequences of enzymatic responses by pancreatic proteases, intestinal alkaline phosphatases, and several matrix metalloproteases are also described. We conclude our insight with a discussion on novel therapeutic interventions derived from crucial aspects of the gut mucosal dynamics during sepsis.

Dysbiosis in early sepsis can be modulated by a multispecies probiotic: a randomised controlled pilot trial

The gut is hypothesised to play an important role in the development and progression of sepsis. It is however unknown whether the gut microbiome and the gut barrier function is already altered early in sepsis development and whether it is possible to modulate the microbiome in early sepsis. Therefore, a randomised, double blind, placebo-controlled pilot study to examine the alterations of the microbiome and the gut barrier in early sepsis and the influence of a concomitant probiotic intervention on dysbiosis at this early stage of the disease was conducted. Patients with early sepsis, defined as fulfilling the sepsis definition from the 2012 Surviving Sepsis Campaign guidelines but without signs of organ failure, received multispecies probiotic (Winclove 607 based on Omnibiotic® 10 AAD) for 28 days. Gut microbiome composition, function, gut barrier and bacterial translocation were studied. Patients with early sepsis had a significantly lower structural and functional alpha diversity, clustered differently and showed structural alterations on all taxonomic levels. Gut permeability was unaltered but endotoxin, endotoxin binding proteins and peptidoglycans were elevated in early sepsis patients compared to controls. Probiotic intervention successfully increased probiotic strains in stool and led to an improvement of functional diversity. Microbiome composition and function are altered in early sepsis. Probiotic intervention successfully modulates the microbiome and is therefore a promising tool for early intervention in sepsis.

Rationalizing antimicrobial therapy in the ICU: a narrative review

The massive consumption of antibiotics in the ICU is responsible for substantial ecological side effects that promote the dissemination of multidrug-resistant bacteria (MDRB) in this environment. Strikingly, up to half of ICU patients receiving empirical antibiotic therapy have no definitively confirmed infection, while de-escalation and shortened treatment duration are insufficiently considered in those with documented sepsis, highlighting the potential benefit of implementing antibiotic stewardship programs (ASP) and other quality improvement initiatives. The objective of this narrative review is to summarize the available evidence, emerging options, and unsolved controversies for the optimization of antibiotic therapy in the ICU. Published data notably support the need for better identification of patients at risk of MDRB infection, more accurate diagnostic tools enabling a rule-in/rule-out approach for bacterial sepsis, an individualized reasoning for the selection of single-drug or combination empirical regimen, the use of adequate dosing and administration schemes to ensure the attainment of pharmacokinetics/pharmacodynamics targets, concomitant source control when appropriate, and a systematic reappraisal of initial therapy in an attempt to minimize collateral damage on commensal ecosystems through de-escalation and treatment-shortening whenever conceivable. This narrative review also aims at compiling arguments for the elaboration of actionable ASP in the ICU, including improved patient outcomes and a reduction in antibiotic-related selection pressure that may help to control the dissemination of MDRB in this healthcare setting.

Altered Metabolic Profile of Triglyceride-Rich Lipoproteins in Gut-Lymph of Rodent Models of Sepsis and Gut Ischemia-Reperfusion Injury

BACKGROUND

Triglyceride-rich lipoproteins are important in dietary lipid absorption and subsequent energy distribution in the body. Their importance in the gut-lymph may have been overlooked in sepsis, the most common cause of critical illness, and in gut ischemia-reperfusion injury, a common feature of many critical illnesses.

AIMS

We aimed to undertake an exploratory study of triglyceride-rich lipoprotein fractions in gut-lymph using untargeted metabolic profiling to identify altered metabolites in sepsis or gut ischemia-reperfusion.

METHODS

The gut-lymph was collected from rodent sham, sepsis, and gut ischemia-reperfusion models. The triglyceride-rich lipoprotein-enriched fractions isolated from the gut-lymph were subjected to a dual metabolomics analysis approach: non-polar metabolite analysis by ultra-high performance liquid chromatography-mass spectrometry and polar metabolite analysis by gas chromatography-mass spectrometry.

RESULTS

The metabolite analysis of gut-lymph triglyceride-rich lipoprotein fractions revealed a significant increase (FDR-adjusted P value < 0.05) in myo-inositol in the sepsis group and monoacylglycerols [(18:1) and (18:2)] in gut ischemia-reperfusion. There were no significantly increased specific metabolites in the lipoprotein-enriched fractions of both sepsis and gut ischemia-reperfusion. In contrast, there was a widespread decrease in multiple lipid species in sepsis (35 out of 190; adjusted P < 0.05), but not in the gut ischemia-reperfusion.

CONCLUSIONS

Increased levels of myo-inositol and monoacylglycerols, and decreased multiple lipid species in the gut-lymph triglyceride-rich lipoprotein fraction could be candidates for new biomarkers and/or involved in the progression of sepsis and gut ischemia-reperfusion pathobiology.

Gut Microbiota Disruption in Septic Shock Patients: A Pilot Study

BACKGROUND The composition of the intestinal microbiota and its effect on septic shock patients in the intensive care unit (ICU) is unknown. In the present study we explored the hypothesis that bacterial diversity is decreased in septic shock patients and that this diversity may be improved by use of probiotics or enteral nutrition. MATERIAL AND METHODS A total of 15 stool samples were collected prospectively from septic shock patients in the ICU, while 15 samples from healthy subjects served as controls. Bacterial DNA was submitted for 16S rDNA gene sequencing. The relationship between intestinal microbiota and prognosis was evaluated. RESULTS Significantly lower bacterial diversity was found in septic shock patients compared with healthy subjects (p<0.05). However, there was no difference in bacterial diversity in the presence or absence of probiotics (p=0.59), enteral nutrition (p=0.59), or in-hospital death (p=0.93) in septic shock patients. A high abundance of Proteobacteria and Fusobacteria was observed in most septic shock patients, whereas low abundance was observed in healthy subjects (mean relative proportion: 23.71% vs. 3.53%, p<0.05; 1.27% vs. 0.12%, p=0.59). CONCLUSIONS Bacterial diversity was decreased, and 1 or 2 rare bacterial species were overgrown in septic shock patients. Bacterial diversity was not improved by use of probiotics or enteral nutrition. The small sample size of our study limits the interpretation of results.

Intestinal hyperpermeability: a gateway to multi-organ failure?

In critically ill patients, disruption of intestinal epithelial cell function occurs due to exposure of the epithelium to toxic internal and external inflammatory stimuli, which are key factors that trigger sepsis and multi-organ dysfunction syndrome (MODS). A greater understanding of how trauma and gut failure lead to sepsis and progression to MODS is much needed. In this issue of the JCI, Armacki and colleagues identify mechanisms by which thirty-eight-negative kinase 1 (TNK1) promotes the progression from intestinal apoptosis and gut failure to bacterial translocation, sepsis, and MODS. Moreover, the results of this study suggest TNK1 as a potential therapeutic target to prevent sepsis and MODS.

Antibiotic stewardship: Why we must, how we can

Improving our antibiotic use is critical to the safety of our patients and the future of medicine. This can improve patient outcomes, save money, reduce resistance, and help prevent negative consequences such as Clostridium difficile infection. The US Centers for Disease Control and Prevention (CDC) is undertaking a nationwide effort to appropriately improve antibiotic use in inpatient and outpatient settings.

Therapeutic Potential of the Gut Microbiota in the Prevention and Treatment of Sepsis

Alongside advances in understanding the pathophysiology of sepsis, there have been tremendous strides in understanding the pervasive role of the gut microbiota in systemic host resistance. In pre-clinical models, a diverse and balanced gut microbiota enhances host immunity to both enteric and systemic pathogens. Disturbance of this balance increases susceptibility to sepsis and sepsis-related organ dysfunction, while restoration of the gut microbiome is protective. Patients with sepsis have a profoundly distorted composition of the intestinal microbiota, but the impact and therapeutic potential of the microbiome is not well-established in human sepsis. Modulation of the microbiota consists of either resupplying the pool of beneficial microbes by administration of probiotics, improving the intestinal microenvironment to enhance the growth of beneficial species by dietary interventions and prebiotics, or by totally recolonizing the gut with a fecal microbiota transplantation (FMT). We propose that there are three potential opportunities to utilize these treatment modalities over the course of sepsis: to decrease sepsis incidence, to improve sepsis outcome, and to decrease late mortality after sepsis. Exploring these three avenues will provide insight into how disturbances of the microbiota can predispose to, or even perpetuate the dysregulated immune response associated with this syndrome, which in turn could be associated with improved sepsis management.

High Circulating Caspase-Cleaved Keratin 18 Fragments (M30) Indicate Short-Term Mortality in Critically Ill Patients

Caspase-cleaved fragments of the intermediate filament protein keratin 18 (cytokeratin-18 (CK18)) can be detected in serum as M30 levels and may serve as a circulating biomarker indicating apoptosis of epithelial and parenchymal cells. In order to evaluate M30 as a biomarker in critical illness, we analyzed circulating M30 levels in 243 critically ill patients (156 with sepsis, 87 without sepsis) at admission to the medical intensive care unit (ICU), in comparison to healthy controls (n = 32). M30 levels were significantly elevated in ICU patients compared with healthy controls. Circulating M30 was closely associated with disease severity but did not differ between patients with sepsis and ICU patients without sepsis. M30 serum levels were correlated with biomarkers of inflammation, cell injury, renal failure, and liver failure in critically ill patients. Patients that died at the ICU showed increased M30 levels at admission, compared with surviving patients. A similar trend was observed for the overall survival. Regression analyses confirmed that M30 levels are associated with mortality, and patients with M30 levels above 250.8 U/L displayed an excessive short-term mortality. Thus, our data support the utility of circulating levels of the apoptosis-related keratin fragment M30 as a prognostic biomarker at ICU admission.

Experimental human endotoxemia as a model of systemic inflammation

Systemic inflammation plays a pivotal role in a multitude of conditions, including sepsis, trauma, major surgery and burns. However, comprehensive analysis of the pathophysiology underlying this systemic inflammatory response is greatly complicated by variations in the immune response observed in critically ill patients, which is a result of inter-individual differences in comorbidity, comedication, source of infection, causative pathogen, and onset of the inflammatory response. During experimental human endotoxemia, human subjects are challenged with purified endotoxin (lipopolysaccharide) intravenously which induces a short-lived, well-tolerated and controlled systemic inflammatory response, similar to that observed during sepsis. The human endotoxemia model can be conducted in a highly standardized and reproducible manner, using a carefully selected homogenous study population. As such, the experimental human endotoxemia model does not share the aforementioned clinical limitations and enables us to investigate both the mechanisms of systemic inflammation, as well as to evaluate novel (pharmacological) interventions in humans in vivo. The present review provides a detailed overview of the various designs, organ-specific changes, and strengths and limitations of the experimental human endotoxemia model, with the main focus on its use as a translational model for sepsis research.

Imipenem and normal saline with cyclophosphamide have positive effects on the intestinal barrier in rats with sepsis

BACKGROUND

Sepsis is a life-threatening organ dysfunction caused the dysregulation of host inflammatory response and immunosuppression to infection Early recognition and intervention are hence of paramount importance. In this respect the "sepsis bundle" was proposed in 2004 to be instituted in cases of suspected sepsis.

OBJECTIVE AND HYPOTHESIS

We hypothesised that a combination treatment of the sepsis bundle with cyclophosphamide would improve the function of the intestinal mucosa and enhance survival in rats with induced sepsis.

METHODS AND RESULTS

Sprague-Dawley rats were divided into 5 different groups: sham, cecal ligation and puncture (CLP), cyclophosphamide (CTX), imipenem+normal saline (NS) and imipenem+NS+CTX. Cecal ligation and puncture were used for inducing the polymicrobial sepsis. Western-blot was used to measure the occludin protein, and ELISA for examining the plasma level of cytokines IL-6, IL-10 and TNF-α. TUNEL assay for testing the intestinal mucosal apoptosis, and hematoxylin-eosin staining for observing the intestinal mucosal changes. The permeability of intestinal mucosa was determined by the plasma level of FD-70. The results showed that the combination treatment of the sepsis bundle with cyclophosphamide attenuated cytokine levels, inhibited epithelial cell apoptosis and improved the function of the intestinal barrier. The survival rate of the group treated with the combined therapy was significantly higher than that of the other groups.

CONCLUSION

The combination treatment of sepsis bundle with cyclophosphamide improves the function of the intestinal barrier and enhances survival in septic rats.

Gut microbiota and host defense in critical illness

PURPOSE OF REVIEW

The review aims to discuss emerging evidence in the field of microbiome-dependent roles in host defense during critical illness with a focus on lung, kidney, and brain inflammation.

RECENT FINDINGS

The gut microbiota of critical ill patients is characterized by lower diversity, lower abundances of key commensal genera, and in some cases overgrowth by one bacterial genera, a state otherwise known as dysbiosis. Increasing evidence suggests that microbiota-derived components can reach the circulatory system from the gut and modulate immune homeostasis. Dysbiosis might have greater consequences for the critically ill than previously imagined and could contribute to poor outcome. Preclinical studies suggest that impaired communication across the gut - organ axes is associated with brain, lung - and kidney failure.

SUMMARY

In health, a diverse microbiome might enhance host defense, while during critical illness, the dysbiotic microbiome might contribute to comorbidity and organ dysfunction. Future research should be aimed at further establishing the causes and consequences of dysbiosis seen in the critically ill, which will provide perspective for developing new strategies of intervention.

The emerging role of the microbiota in the ICU

This article is one of ten reviews selected from the Annual Update in Intensive Care and Emergency Medicine 2018. Other selected articles can be found online at https://www.biomedcentral.com/collections/annualupdate2018. Further information about the Annual Update in Intensive Care and Emergency Medicine is available from http://www.springer.com/series/8901.

Pathogenesis of Sepsis

Sepsis is a life-threatening organ dysfunction due to a dysregulated host response to infection. Both hyperinflammation and immune suppression ensue, to an extent that is harmful to the host. The inflammatory balance is disturbed, and this is associated with a failure to return to homeostasis.

All pathogens with sufficient load and virulence can cause sepsis, after they succeed to adhere and pass the mucosal barrier of the host. The host defense system can recognize molecular components of invading pathogens, called pathogen-associated molecular patterns (PAMPs), with specialized receptors known as pattern recognition receptors (PRRs). Through several signaling pathways, overstimulation of PRRs has proinflammatory and immune suppressive consequences. Hyperinflammation is characterized by activation of target genes coding for proinflammatory cytokines (leukocyte activation), inefficient use of the complement system, activation of the coagulation system, and concurrent downregulation of anticoagulant mechanisms and necrotic cell death. The release of endogenous molecules by injured cells, called danger-associated molecular patterns (DAMPs) or alarmins, leads to deterioration in a vicious cycle by further stimulation of PRRs. Features of immune suppression are massive apoptosis and thereby depletion of immune cells, reprogramming of monocytes and macrophages to a state of a decreased capacity to release proinflammatory cytokines and a disturbed balance in cellular metabolic processes.

Septic Shock and the Aging Process: A Molecular Comparison

Aging is a continuous process promoted by both intrinsic and extrinsic factors that each trigger a multitude of molecular events. Increasing evidence supports a central role for inflammation in this progression. Here, we discuss how the low-grade chronic inflammation that characterizes aging is tightly interconnected with other important aspects of this process, such as DNA damage, mitochondrial dysfunction, and epigenetic changes. Similarly, inflammation also plays a critical role in many morbid conditions that affect patients who are admitted to Intensive Care. Although the inflammatory response is low grade and persistent in healthy aging while it is acute and severe in critically ill states, we hypothesize that both situations have important interconnections. Here, we performed an extensive review of the literature to investigate this potential link. Because sepsis is the most extensively studied disease and is the leading cause of death in Critical Care, we focus our discussion on comparing the inflammatory profile of healthy older people with that of patients in septic shock to explain why we believe that both situations have synergistic effects, leading to critically ill aged patients having a worse prognosis when compared with critically ill young patients.

Gut Microbiota-Dependent Trimethylamine-N-oxide and Serum Biomarkers in Patients with T2DM and Advanced CKD

Trimethylamine-N-oxide (TMAO) is a product of dietary, gut microbiome, and tissues metabolism. Elevated blood TMAO levels are associated with heart attack, stroke and chronic kidney disease (CKD). The purpose of our study was to investigate the gut microbiota associated with trimethylamine (TMA) production, the precursor of TMAO, and the serum levels of TMAO and inflammatory biomarkers associated with type 2 diabetes mellitus (T2DM) and CKD. Twenty adults with T2DM and advanced CKD and 20 healthy adults participated in the study. Analyses included anthropometric and metabolic parameters, characterization of TMA producing gut microbiota, and concentrations of TMAO, lipopolysaccharides (LPS) endotoxin, zonulin (Zo) gut permeability marker, and serum inflammatory and endothelial dysfunction biomarkers. Diversity of the gut microbiota was identified by amplification of V3-V4 regions of the 16S ribosomal RNA genes and DNA sequencing. TMAO was quantified by Mass Spectrometry and serum biomarkers by ELISA. The significance of measurements justified by statistical analysis. The gut microbiome in T2DM-CKD patients exhibited a higher incidence of TMA-producing bacteria than control, p < 0.05. The serum levels of TMAO in T2DM-CKD patients were significantly higher than controls, p < 0.05. TMAO showed a positive correlation with Zo and LPS, inflammatory and endothelial dysfunction biomarkers. A positive correlation was observed between Zo and LPS in T2DM-CKD subjects. An increased abundance of TMA-producing bacteria in the gut microbiota of T2DM-CKD patients together with excessive TMAO and increased gut permeability might impact their risk for cardiovascular disease through elevation of chronic inflammation and endothelial dysfunction.