Small intestinal bacterial overgrowth in patients with cirrhosis: prevalence and relation with spontaneous bacterial peritonitis

Rejuvenating bone marrow hematopoietic reserve prevents regeneration failure and hepatic decompensation in animal model of cirrhosis

Background and aim

Bone marrow stem cells (BM-SCs) and their progeny play a central role in tissue repair and regeneration. In patients with chronic liver failure, bone marrow (BM) reserve is severally compromised and they showed marked defects in the resolution of injury and infection, leading to liver failure and the onset of decompensation. Whether BM failure is the cause or consequence of liver failure during cirrhosis is not known. In this study, we aimed to determine the underlying relationship between BM failure and regeneration failure in cirrhosis.

Methodology

C57Bl/6(J) mice were used to develop chronic liver injury through intra-peritoneal administration of carbon tetrachloride (CCl4) for 15 weeks (0.1-0.5 ml/kg). Animals were sacrificed to study the transition of cirrhosis and BM defects. To restore the BM-SC reserve; healthy BM cells were infused via intra-BM infusion and assessed for changes in liver injury, regeneration, and BM-SC reserve.

Results

Using a CCl4-induced animal - model of cirrhosis, we showed the loss of BM-SCs reserve occurred before regeneration failure and the onset of non-acute decompensation. Intra-BM infusion of healthy BM cells induced the repopulation of native hematopoietic stem cells (HSCs) in cirrhotic BM. Restoring BM-HSCs reserve augments liver macrophage-mediated clearance of infection and inflammation dampens neutrophil-mediated inflammation, accelerates fibrosis regression, enhances hepatocyte proliferation, and delays the onset of non-acute decompensation.

Conclusion

These findings suggest that loss of BM-HSCs reserve underlies the compromised innate immune function of the liver, drives regeneration failure, and the onset of non-acute decompensation. We further provide the proof-of-concept that rejuvenating BM-HSC reserve can serve as a potential therapeutic approach for preventing regeneration failure and transition to decompensated cirrhosis.

Infectious Complications of Portal Hypertension

Patients with cirrhosis and clinically significant portal hypertension are at high risk of developing bacterial infections (BIs) that are the most common trigger of acute decompensation and acute-on-chronic liver failure. Furthermore, after decompensation, the risk of developing BIs further increases in an ominous vicious circle. BIs may be subtle, and they should be ruled out in all patients at admission and in case of deterioration. Timely administration of adequate empirical antibiotics is the cornerstone of treatment. Herein, we reviewed current evidences about pathogenesis, clinical implications and management of BIs in patients with cirrhosis and portal hypertension.

Fecal microbiota transplantation in the treatment of hepatic encephalopathy: A perspective

Due to its complex pathogenesis, treatment of hepatic encephalopathy (HE) continues to be a therapeutic challenge. Of late, gut microbiome has garnered much attention for its role in the pathogenesis of various gastrointestinal and liver diseases and its potential therapeutic use. New evidence suggests that gut microbiota plays a significant role in cerebral homeostasis. Alteration in the gut microbiota has been documented in patients with HE in a number of clinical and experimental studies. Research on gut dysbiosis in patients with HE has opened newer therapeutic avenues in the form of probiotics, prebiotics and the latest fecal microbiota transplantation (FMT). Recent studies have shown that FMT is safe and could be effective in improving outcomes in advanced liver disease patients presenting with HE. However, questions over the appropriate dose, duration and route of administration for best treatment outcome remains unsettled.

Changes of the bacterial composition in duodenal fluid from patients with liver cirrhosis and molecular bacterascites

Small intestinal bacterial overgrowth and compositional changes of intestinal microbiota are pathomechanistic factors in liver cirrhosis leading to bacterial translocation and infectious complications. We analyzed the quantity and composition of duodenal bacterial DNA (bactDNA) in relation to bactDNA in blood and ascites of patients with liver cirrhosis. Duodenal fluid and corresponding blood and ascites samples from 103 patients with liver cirrhosis were collected. Non-liver disease patients (n = 22) served as controls. BactDNA was quantified by 16S-rRNA gene-based PCR. T-RFLP and 16S-rRNA amplicon sequencing were used to analyze bacterial composition. Duodenal bacterial diversity in cirrhosis was distinct to controls showing significantly higher abundances of Streptococcus, Enterococcus and Veillonella. Patients with bactDNA positive ascites revealed reduced spectrum of core microbiota with Streptococcus as key player of duodenal community and higher prevalence of Granulicatella proving presence of cirrhosis related intestinal dysbiosis. Regarding duodenal fluid bactDNA quantification, no significant differences were found between patients with cirrhosis and controls. Additionally, percentage of subjects with detectable bactDNA in blood did not differ between patients and controls. This study evaluated the diversity of bacterial DNA in different body specimens with potential implications on understanding how intestinal bacterial translocation may affect infectious complications in cirrhosis.

Hepatic Encephalopathy in Acute-on-Chronic Liver Failure

Acute-on-chronic liver failure (ACLF) is characterized by the presence of chronic liver disease and extrahepatic organ failure and is associated with a high rate of short-term mortality. International societies have sought to define the criteria for ACLF and differ on definitions. Encephalopathy is an important organ failure in ACLF cases and is included as a marker of ACLF across society definitions. Both brain failure and ACLF commonly occur in the presence of a triggering event and in the setting of the large amount of inflammation that ensues. The presence of encephalopathy as a part of ACLF not only increases the chances of mortality but also provides unique challenges in that the patient will be limited in conversations around major decisions such as need for advanced level of care, liver transplant, or even end-of-life decisions. Many decisions need to be made quickly and occur in parallel in the care of patients with encephalopathy and ACLF and include stabilizing the patient, identifying precipitants or alternative diagnoses, and medical management. Infections has emerged as a major trigger for both ACLF and encephalopathy, and special attention should be given to identifying and treating infections as they occur.

Small Intestinal Bacterial Overgrowth Is Associated with Poor Prognosis in Cirrhosis

BACKGROUND

Small intestinal bacterial overgrowth (SIBO) is associated with numerous manifestations of cirrhosis. To determine whether the presence of SIBO affects the prognosis in cirrhosis was the aim of the study.

METHODS

This prospective cohort study included 50 patients. All participants underwent a lactulose hydrogen breath test for SIBO. The follow-up period was 4 years.

RESULTS

SIBO was detected in 26 (52.0%) patients: in 10 (52.6%) patients with compensated cirrhosis and in 16 (51.6%) ones with decompensated cirrhosis. Twelve (46.2%) patients with SIBO and four (16.7%) patients without SIBO died within 4 years (p = 0.009). Among patients with decompensated cirrhosis, 8 (50.0%) patients with SIBO and 3 (20.0%) patients without SIBO died (p = 0.027). Among patients with compensated cirrhosis, four (40.0%) patients with SIBO and one (11.1%) patient without SIBO died (p = 0.045). Among patients with SIBO, there was no difference in mortality between patients with compensated and decompensated cirrhosis (p = 0.209). It was the same for patients without SIBO (p = 0.215). SIBO affects the prognosis only in the first year of follow-up in decompensated cirrhosis, and only in subsequent years in compensated cirrhosis. Presence of SIBO (p = 0.028; HR = 4.2(1.2-14.9)) and serum albumin level (p = 0.027) were significant independent risk factors for death in cirrhosis.

CONCLUSIONS

SIBO is associated with poor prognosis in cirrhosis.

The Role of Microbiota in Liver Transplantation and Liver Transplantation-Related Biliary Complications

Liver transplantation as a treatment option for end-stage liver diseases is associated with a relevant risk for complications. On the one hand, immunological factors and associated chronic graft rejection are major causes of morbidity and carry an increased risk of mortality due to liver graft failure. On the other hand, infectious complications have a major impact on patient outcomes. In addition, abdominal or pulmonary infections, and biliary complications, including cholangitis, are common complications in patients after liver transplantation and can also be associated with a risk for mortality. Thereby, these patients already suffer from gut dysbiosis at the time of liver transplantation due to their severe underlying disease, causing end-stage liver failure. Despite an impaired gut-liver axis, repeated antibiotic therapies can cause major changes in the gut microbiome. Due to repeated biliary interventions, the biliary tract is often colonized by several bacteria with a high risk for multi-drug resistant germs causing local and systemic infections before and after liver transplantation. Growing evidence about the role of gut microbiota in the perioperative course and their impact on patient outcomes in liver transplantation is available. However, data about biliary microbiota and their impact on infectious and biliary complications are still sparse. In this comprehensive review, we compile the current evidence for the role of microbiome research in liver transplantation with a focus on biliary complications and infections due to multi-drug resistant germs.

Hepatic Encephalopathy

Hepatic encephalopathy (HE) is brain dysfunction secondary to liver insufficiency or portosystemic shunting. HE is a major burden on patients and caregivers, impairs quality of life and is associated with higher mortality. Overt HE is a clinical diagnosis while Covert HE, needs specialized diagnostic strategies. Mainstay of treatment of HE is nonabsorbable disaccharides such as lactulose as well as rifaximin; however, investigational therapies are discussed in this review. Better tools are needed to prognosticate which patients will go on to develop HE but microbiome and metabolomic-driven strategies are promising. Here we review methods to prevent the HE development and admissions.

Is it possible to intervene early cirrhosis by targeting toll-like receptors to rebalance the intestinal microbiome?

Cirrhosis is a progressive chronic liver disease caused by one or more causes and characterized by diffuse fibrosis, pseudolobules, and regenerated nodules. Once progression to hepatic decompensation, the function of the liver and other organs is impaired and almost impossible to reverse and recover, which often results in hospitalization, impaired quality of life, and high mortality. However, in the early stage of cirrhosis, there seems to be a possibility of cirrhosis reversal. The development of cirrhosis is related to the intestinal microbiota and activation of toll-like receptors (TLRs) pathways, which could regulate cell proliferation, apoptosis, expression of the hepatomitogen epiregulin, and liver inflammation. Targeting regulation of intestinal microbiota and TLRs pathways could affect the occurrence and development of cirrhosis and its complications. In this paper, we first reviewed the dynamic change of intestinal microbiota and TLRs during cirrhosis progression. And further discussed the interaction between them and potential therapeutic targets to reverse early staged cirrhosis.

Altered gut microbiota in patients with small intestinal bacterial overgrowth

BACKGROUND AND AIM

Small intestinal bacterial overgrowth (SIBO) is diagnosed by using quantitative culture of duodenal aspirates and/or a hydrogen breath test. However, few studies have analyzed bacterial microbiota in Japanese patients with SIBO.

METHODS

Twenty-four patients with any abdominal symptoms and suspected SIBO were enrolled. Quantitative culture of duodenal aspirates and a glucose hydrogen breath test were performed on the same day. SIBO was diagnosed based on a bacterial count ≥ 10³  CFU/mL or a rise in the hydrogen breath level of ≥ 20 ppm. The composition of the duodenal microbiota was analyzed by 16S rRNA gene sequencing.

RESULTS

Small intestinal bacterial overgrowth was diagnosed in 17 of the 24 patients (71%). The positive rates for the hydrogen breath test and quantitative culture of duodenal aspirates were 50% and 62%, respectively. Patients with SIBO showed significantly reduced α-diversity compared with non-SIBO patients, and analysis of β-diversity revealed significantly different distributions between SIBO and non-SIBO patients. In addition, the intestinal microbiome in SIBO patients was characterized by increased relative abundance of Streptococcus and decreased relative abundance of Bacteroides compared with non-SIBO patients.

CONCLUSIONS

Duodenal dysbiosis was identified in patients with SIBO and may play a role in the pathophysiology of SIBO.

The Prevalence of Small Intestinal Bacterial Overgrowth in Patients with Non-Alcoholic Liver Diseases: NAFLD, NASH, Fibrosis, Cirrhosis-A Systematic Review, Meta-Analysis and Meta-Regression

Bacterial overgrowth in the small intestine (SIBO) is a pathological growth of the intestinal microbiota in the small intestine that causes clinical symptoms and can lead to digestive and absorption disorders. There is increasing evidence that people with NAFLD have a distinct gut microflora profile as well metabolome changes compared to people without NAFLD. Thorough analysis of observational and RCT studies in the current databases (EMBASE, Web of Science, PubMed, Cinahl, Clinical Trials) was conducted from 3 November 2021 to 21 June 2022. The following inclusion criteria were applied: confirmed NAFLD, NASH, LIVER FIBROSIS, CIRRHOSIS due to steatosis; diagnostic methods of liver diseases—biopsy, elastography, transabdominal ultrasound; nonalcoholic fatty liver disease activity score; confirmed SIBO; diagnostic methods of SIBO−breath tests (hydrogen test; methane test and mix test; duodenal and jejunal aspiration before any type of intervention; adults above 18yo; number of participants ≥20; full articles. We excluded review articles, populations with HBV/HCV infection and alcohol etiology and interventions that may affect NAFLD or SIBO treatment. The quality of each study methodology was classified by means of the Cochrane Collaboration’s tool (RCT) and Newcastle—Ottawa Quality Assessment Scale adapted for cross-sectional, cohort and case-control studies. The random effects meta-analysis of outcomes for which ≥2 studies contributed data was conducted. The I2 index to measure heterogeneity and the χ2 test of homogeneity (statistically significant heterogeneity p < 0.05) were applied. For categorical outcome, the pooled event rate (effect size) was calculated. This systematic review was reported according to PRISMA reporting guidelines. We initially identified 6643 studies, from which 18 studies were included in final meta-analysis. The total number of patients was 1263. Accepted SIBO diagnostic methods were both available breath tests (n-total = 15) and aspirate culture (n-total = 3). We found that among patients with non-alcoholic liver diseases, the random overall event rate of SIBO was 0.350 (95% CI, 0.244−0.472), p = 0.017. The subgroup analysis regarding a type of diagnosis revealed that the lowest ER was among patients who developed simultaneously NAFLD, NASH and fibrosis: 0.197 (95% CI, 0.054−0.510) as compared to other annotated subgroups. The highest prevalence of SIBO was observed in the NASH subgroup: 0.411 (95% CI, 0.219−0.634). There were no statistically significant differences in the prevalence of SIBO in different subgroups (p = 0.854). Statistically significant heterogeneity between studies was estimated (I2 = 86.17%, p = 0.00). Egger’s test did not indicate a publication bias (df = 16, p = 0.885). A meta-regression using a random-effects model revealed that higher percentage of males in the population with liver diseases is a predisposing factor toward SIBO (Q = 4.11, df = 1, p = 0.0426 with coefficient = 0.0195, SE = 0.0096, Z = 2.03). We showed that the prevalence of SIBO in patients with chronic non-alcoholic liver diseases can be as high as 35%, and it increases with the percentage of men in the population. The prevalence of SIBO does not differ significantly depending on the type of chronic liver disease. Despite the high heterogeneity and moderate and low quality of included studies, our meta-analysis suggests the existence of a problem of SIBO in the population of patients with non-alcoholic liver diseases, and the presence of SIBO, in turn, determines the therapeutic treatment of such type of patients, which indicates the need for further research in this area. The study protocol was registered with the international Prospective Register of Systematic Reviews (PROSPERO ID: CRD42022341473).

The Association Between Proton Pump Inhibitor Exposure and Key Liver-Related Outcomes in Patients With Cirrhosis: A Veterans Affairs Cohort Study

BACKGROUND & AIMS

The impact of proton pump inhibitory (PPI) medications on adverse outcomes in cirrhosis remains controversial. We aimed to evaluate the association between PPI exposure and all-cause mortality, infection, and decompensation in a large national cohort.

METHODS

This was a retrospective study of patients with cirrhosis in the Veterans Health Administration. PPI exposure was classified as a time-updating variable from the index time of the cirrhosis diagnosis. Inverse probability treatment weighting-adjusted Cox regression was performed with additional adjustment for key time-varying covariates, including cardiovascular comorbidities, gastrointestinal bleeding (GIB), and statin exposure.

RESULTS

The study included 76,251 patients, 23,628 of whom were on a PPI at baseline. In adjusted models, binary (yes/no) PPI exposure was associated with reduced hazard of all-cause mortality in patients with hospitalization for GIB (hazard ratio [HR], 0.88; 95% confidence interval [CI], 0.84-0.91; P < .001) but had no significant association in all others (HR, 0.99; 95% CI, 0.97-1.02; P = .58). However, cumulative PPI exposure was associated with increased mortality in patients without hospitalization for GIB (HR, 1.07 per 320 mg-months [omeprazole equivalents]; 95% CI, 1.06-1.08; P < .001). PPI exposure was significantly associated with severe infection (HR, 1.21; 95% CI, 1.18-1.24; P < .001) and decompensation (HR, 1.64; 95% CI, 1.61-1.68; P < .001). In a cause-specific mortality analysis, PPI exposure was associated with increased liver-related mortality (HR, 1.23; 95% CI, 1.19-1.28) but with decreased nonliver-related mortality (HR, 0.88; 95% CI, 0.85-0.91).

CONCLUSIONS

PPI exposure is associated with increased risk of infection and decompensation in cirrhosis, which may mediate liver-related mortality. However, PPI use was associated with reduced all-cause mortality in those with prior GIB, suggesting benefit in the presence of an appropriate indication.

Liver Steatosis: A Marker of Metabolic Risk in Children

Obesity is one of the greatest health challenges affecting children of all ages and ethnicities. Almost 19% of children and adolescents worldwide are overweight or obese, with an upward trend in the last decades. These reports imply an increased risk of fat accumulation in hepatic cells leading to a series of histological hepatic damages gathered under the acronym NAFLD (Non-Alcoholic Fatty Liver Disease). Due to the complex dynamics underlying this condition, it has been recently renamed as 'Metabolic Dysfunction Associated Fatty Liver Disease (MAFLD)', supporting the hypothesis that hepatic steatosis is a key component of the large group of clinical and laboratory abnormalities of Metabolic Syndrome (MetS). This review aims to share the latest scientific knowledge on MAFLD in children in an attempt to offer novel insights into the complex dynamics underlying this condition, focusing on the novel molecular aspects. Although there is still no treatment with a proven efficacy for this condition, starting from the molecular basis of the disease, MAFLD's therapeutic landscape is rapidly expanding, and different medications seem to act as modifiers of liver steatosis, inflammation, and fibrosis.

Asian-Pacific consensus on small intestinal bacterial overgrowth in gastrointestinal disorders: An initiative of the Indian Neurogastroenterology and Motility Association

In the clinical setting, small intestinal bacterial overgrowth (SIBO) is a frequent, but under-diagnosed entity. SIBO is linked to various gastrointestinal (GI) and non-GI disorders with potentially significant morbidity. The optimal management of SIBO is undefined while there is a lack of published consensus guidelines. Against this background, under the auspices of the Indian Neurogastroenterology and Motility Association (INMA), formerly known as the Indian Motility and Functional Diseases Association (IMFDA), experts from the Asian-Pacific region with extensive research and clinical experience in the field of gut dysbiosis including SIBO developed this evidence-based practice guideline for the management of SIBO utilizing a modified Delphi process based upon 37 consensus statements, involving an electronic voting process as well as face-to-face meetings and review of relevant supporting literature. These statements include 6 statements on definition and epidemiology; 11 on etiopathogenesis and pathophysiology; 5 on clinical manifestations, differential diagnosis, and predictors; and 15 on investigations and treatment. When the proportion of those who voted either to accept completely or with minor reservations was 80% or higher, the statement was regarded as accepted. The members of the consensus team consider that this guideline would be valuable to inform clinical practice, teaching, and research on SIBO in the Asian-Pacific region as well as in other countries.

Role of Microbiota-Derived Metabolites in Alcoholic and Non-Alcoholic Fatty Liver Diseases

Chronic liver disease encompasses diseases that have various causes, such as alcoholic liver disease (ALD) and non-alcoholic fatty liver disease (NAFLD). Gut microbiota dysregulation plays a key role in the pathogenesis of ALD and NAFLD through the gut-liver axis. The gut microbiota consists of various microorganisms that play a role in maintaining the homeostasis of the host and release a wide number of metabolites, including short-chain fatty acids (SCFAs), peptides, and hormones, continually shaping the host's immunity and metabolism. The integrity of the intestinal mucosal and vascular barriers is crucial to protect liver cells from exposure to harmful metabolites and pathogen-associated molecular pattern molecules. Dysbiosis and increased intestinal permeability may allow the liver to be exposed to abundant harmful metabolites that promote liver inflammation and fibrosis. In this review, we introduce the metabolites and components derived from the gut microbiota and discuss their pathologic effect in the liver alongside recent advances in molecular-based therapeutics and novel mechanistic findings associated with the gut-liver axis in ALD and NAFLD.

Proton Pump Inhibitor Therapy Does Not Affect Prognosis of Cirrhosis Patients With Acute Decompensation and Acute-on-Chronic Liver Failure: A Single-Center Prospective Study

Background: The aim of this study was to investigate the impact of proton pump inhibitor (PPI) therapy on complications and prognosis in cirrhosis patients with and without acute-on-chronic liver failure (ACLF).

Materials and Methods: Cirrhosis patients with acute decompensation (AD) (n = 489) admitted in our center were enrolled in this prospective observational cohort study. According to treatment received, patients were identified as users or nonusers of PPI. Clinical and laboratory data, complications during hospitalization, and overall survival were recorded in all the patients.

Results: Of the 489 patients, 299 (61.1%) patients received PPI therapy. The logistic regression analysis showed that age, albumin, history of previous hepatic encephalopathy (HE), and the chronic liver failure-sequential organ failure assessment (CLIF-SOFA) score were independent risk factors for HE in patients with decompensated cirrhosis [odds ratio (OR) = 1.07, 95% CI: 1.03–1.12, p = 0.001; OR = 1.13, 95% CI: 1.04–1.24, p = 0.006; OR = 242.52, 95% CI: 40.17–1464.11, p < 0.001; and OR = 2.89, 95% CI: 2.11–3.96, p < 0.001, respectively]. Previous severe liver injury and previous bacterial infections were independent risk factors for spontaneous bacterial peritonitis (SBP) in patients with decompensated cirrhosis (OR = 3.43, 95% CI: 1.16–10.17, p = 0.026 and OR = 6.47, 95% CI: 2.29–18.29, p < 0.001, respectively). The multivariate Cox proportional hazards regression model showed that the type and dose of the PPI used were not related to 28-day and 90-day mortality in cirrhosis patients with AD or ACLF.

Conclusion: PPI use does not appear to increase mortality or the risk of HE and SBP in the hospitalized cirrhosis patients with and without ACLF.

An Epidemiological Meta-Analysis on the Worldwide Prevalence, Resistance, and Outcomes of Spontaneous Bacterial Peritonitis in Cirrhosis

Background and Aims: Spontaneous bacterial peritonitis (SBP) is a common and potentially fatal complication of liver cirrhosis. This study aims to analyze the prevalence of SBP among liver cirrhotic patients according to geographical location and income level, and risk factors and outcomes of SBP. Methods: A systematic search for articles describing prevalence, risk factors and outcomes of SBP was conducted. A single-arm meta-analysis was performed using generalized linear mix model (GLMM) with Clopper-Pearson intervals. Results: Ninety-Nine articles, comprising a total of 5,861,142 individuals with cirrhosis were included. Pooled prevalence of SBP was found to be 17.12% globally (CI: 13.63-21.30%), highest in Africa (68.20%; CI: 12.17-97.08%), and lowest in North America (10.81%; CI: 5.32-20.73%). Prevalence of community-acquired SBP was 6.05% (CI: 4.32-8.40%), and 11.11% (CI: 5.84-20.11%,) for healthcare-associated SBP. Antibiotic-resistant microorganisms were found in 11.77% (CI: 7.63-17.73%) of SBP patients. Of which, methicillin-resistant Staphylococcus aureus was most common (6.23%; CI: 3.83-9.97%), followed by extended-spectrum beta-lactamase producing organisms (6.19%; CI: 3.32-11.26%), and lastly vancomycin-resistant enterococci (1.91%; CI: 0.41-8.46%). Subgroup analysis comparing prevalence, antibiotic resistance, and outcomes between income groups was conducted to explore a link between socioeconomic status and SBP, which revealed decreased risk of SBP and negative outcomes in high-income countries. Conclusion: SBP remains a frequent complication of liver cirrhosis worldwide. The drawn link between income level and SBP in liver cirrhosis may enable further insight on actions necessary to tackle the disease on a global scale.

The microbiota in cirrhosis and its role in hepatic decompensation

Cirrhosis - the common end-stage of chronic liver disease - is associated with a cascade of events, of which intestinal bacterial overgrowth and dysbiosis are central. Bacterial toxins entering the portal or systemic circulation can directly cause hepatocyte death, while dysbiosis also affects gut barrier function and increases bacterial translocation, leading to infections, systemic inflammation and vasodilation, which contribute to acute decompensation and organ failure. Acute decompensation and its severe forms, pre-acute-on-chronic liver failure (ACLF) and ACLF, are characterised by sudden organ dysfunction (and failure) and high short-term mortality. Patients with pre-ACLF and ACLF present with high-grade systemic inflammation, usually precipitated by proven bacterial infection and/or severe alcoholic hepatitis. However, no precipitant is identified in 30% of these patients, in whom bacterial translocation from the gut microbiota is assumed to be responsible for systemic inflammation and decompensation. Different microbiota profiles may influence the rate of decompensation and thereby outcome in these patients. Thus, targeting the microbiota is a promising strategy for the prevention and treatment of acute decompensation, pre-ACLF and ACLF. Approaches include the use of antibiotics such as rifaximin, faecal microbial transplantation and enterosorbents (e.g. Yaq-001), which bind microbial factors without exerting a direct effect on bacterial growth kinetics. This review focuses on the role of microbiota in decompensation and strategies targeting microbiota to prevent acute decompensation.

The Gut-Liver Axis in Cholestatic Liver Diseases

The gut-liver axis describes the physiological interplay between the gut and the liver and has important implications for the maintenance of health. Disruptions of this equilibrium are an important factor in the evolution and progression of many liver diseases. The composition of the gut microbiome, the gut barrier, bacterial translocation, and bile acid metabolism are the key features of this cycle. Chronic cholestatic liver diseases include primary sclerosing cholangitis, the generic term secondary sclerosing cholangitis implying the disease secondary sclerosing cholangitis in critically ill patients and primary biliary cirrhosis. Pathophysiology of these diseases is not fully understood but seems to be multifactorial. Knowledge about the alterations of the gut-liver axis influencing the pathogenesis and the outcome of these diseases has considerably increased. Therefore, this review aims to describe the function of the healthy gut-liver axis and to sum up the pathological changes in these cholestatic liver diseases. The review compromises the actual level of knowledge about the gut microbiome (including the mycobiome and the virome), the gut barrier and the consequences of increased gut permeability, the effects of bacterial translocation, and the influence of bile acid composition and pool size in chronic cholestatic liver diseases. Furthermore, therapeutic implications and future scientific objectives are outlined.

Pathophysiology and Management of Variceal Bleeding

Cirrhosis is the fifth leading cause of death in adults. Advanced cirrhosis can cause significant portal hypertension (PH), which is responsible for many of the complications observed in patients with cirrhosis, such as varices. If portal pressure exceeds a certain threshold, the patient is at risk of developing life-threatening bleeding from varices. Variceal bleeding has a high incidence among patients with liver cirrhosis and carries a high risk of mortality and morbidity. The management of variceal bleeding is complex, often requiring a multidisciplinary approach involving pharmacological, endoscopic, and radiologic interventions. In terms of management, three stages can be considered: primary prophylaxis, active bleeding, and secondary prophylaxis. The main goal of primary and secondary prophylaxis is to prevent variceal bleeding. However, active variceal bleeding is a medical emergency that requires swift intervention to stop the bleeding and achieve durable hemostasis. We describe the pathophysiology of cirrhosis and PH to contextualize the formation of gastric and esophageal varices. We also discuss the currently available treatments and compare how they fare in each stage of clinical management, with a special focus on drugs that can prevent bleeding or assist in achieving hemostasis.

GUT MICROBIOTA, PREBIOTICS, PROBIOTICS, AND SYNBIOTICS IN GASTROINTESTINAL AND LIVER DISEASES: PROCEEDINGS OF A JOINT MEETING OF THE BRAZILIAN SOCIETY OF HEPATOLOGY (SBH), BRAZILIAN NUCLEUS FOR THE STUDY OF HELICOBACTER PYLORI AND MICROBIOTA (NBEHPM), AND BRAZILIAN FEDERATION OF GASTROENTEROLOGY (FBG)

Over the last years, there is growing evidence that microorganisms are involved in the maintenance of our health and are related to various diseases, both intestinal and extraintestinal. Changes in the gut microbiota appears to be a key element in the pathogenesis of hepatic and gastrointestinal disorders, including non-alcoholic fatty liver disease, alcoholic liver disease, liver cirrhosis, inflammatory bowel disease, irritable bowel syndrome, and Clostridium difficile - associated diarrhea. In 2019, the Brazilian Society of Hepatology (SBH) in cooperation with the Brazilian Nucleus for the Study of Helicobacter Pylori and Microbiota (NBEHPM), and Brazilian Federation of Gastroenterology (FBG) sponsored a joint meeting on gut microbiota and the use of prebiotics, probiotics, and synbiotics in gastrointestinal and liver diseases. This paper summarizes the proceedings of the aforementioned meeting. It is intended to provide practical information about this topic, addressing the latest discoveries and indicating areas for future studies.

Gut Microbiota Modulation and Fecal Transplantation: An Overview on Innovative Strategies for Hepatic Encephalopathy Treatment

Hepatic encephalopathy (HE) is a major complication of cirrhosis, which is associated with gut microbial composition and functional alterations. Current treatments largely focus on gut microbiota using lactulose, rifaximin and other agents. However, despite these treatments, patients with HE have a high rate of readmission, morbidity and cognitive impairment. Fecal microbiota transplant (FMT) involves introduction of a donor microbiota into a recipient and is currently mainly used for recurrent C. difficile infection (rCDI). The role of FMT in cirrhosis and HE is evolving. There have been two randomized clinical trials (RCT) and several case reports/series in cirrhosis. Both RCTs were safety-focused phase 1 trials. One involved pre-FMT antibiotics and FMT enema versus standard of care, while the other involved 15 FMT capsules versus placebo without pre-FMT antibiotics. There was evidence of safety in both trials and the FMT group demonstrated reduction in hospitalizations compared to the non-FMT group. Changes in microbial function centered around short-chain fatty acids, bile acids and brain function showed improvement in the FMT groups. Long-term follow-up demonstrated continued safety and reduction in the antibiotic-resistance gene carriage. However, larger trials of FMT in HE are needed that can refine the dose, duration and route of FMT administration.

New Developments in Microbiome in Alcohol-Associated and Nonalcoholic Fatty Liver Disease

Alcohol-associated liver disease (ALD) and nonalcoholic fatty liver disease (NAFLD) are important causes of morbidity and mortality worldwide. The intestinal microbiota is involved in the development and progression of both ALD and NAFLD. Here we describe associated changes in the intestinal microbiota, and we detail randomized clinical trials in ALD and NAFLD which evaluate treatments modulating the intestinal microbiome including fecal microbiota transplantation, probiotics, prebiotics, synbiotics, and antibiotics. Finally, we discuss precision medicine approaches targeting the intestinal microbiome to ameliorate ALD and NAFLD.

Pediatric Non-Alcoholic Fatty Liver Disease: Nutritional Origins and Potential Molecular Mechanisms

Non-alcoholic fatty liver disease (NAFLD) is the number one chronic liver disease worldwide and is estimated to affect nearly 40% of obese youth and up to 10% of the general pediatric population without any obvious signs or symptoms. Although the early stages of NAFLD are reversible with diet and lifestyle modifications, detecting such stages is hindered by a lack of non-invasive methods of risk assessment and diagnosis. This absence of non-invasive means of diagnosis is directly related to the scarcity of long-term prospective studies of pediatric NAFLD in children and adolescents. In the majority of pediatric NAFLD cases, the mechanisms driving the origin and rapid progression of NAFLD remain unknown. The progression from NAFLD to non-alcoholic steatohepatitis (NASH) in youth is associated with unique histological features and possible immune processes and metabolic pathways that may reflect different mechanisms compared with adults. Recent data suggest that circulating microRNAs (miRNAs) are important new biomarkers underlying pathways of liver injury. Several factors may contribute to pediatric NAFLD development, including high-sugar diets, in utero exposures via epigenetic alterations, changes in the neonatal microbiome, and altered immune system development and mitochondrial function. This review focuses on the unique aspects of pediatric NAFLD and how nutritional exposures impact the immune system, mitochondria, and liver/gastrointestinal metabolic health. These factors highlight the need for answers to how NAFLD develops in children and for early stage-specific interventions.

Predictors of Small Intestinal Bacterial Overgrowth in Symptomatic Patients Referred for Breath Testing

Background

Indications for a breath test (BT) are well established in the symptomatic patient with risk factors predisposing them to small intestinal bacterial overgrowth (SIBO). Characteristics and the profile of this population are not well known. Our objective was to study the characteristics of patients undergoing a BT for SIBO and to identify factors associated with a positive BT.

Methods

Retrospective study was conducted from 2012 to 2016 at the neurogastroenterology unit of the Centre Hospitalier de l'Universite de Montreal (CHUM). All patients who completed a BT (lactulose and/or glucose) were included. Demographics and clinical factors were analyzed to identify predictors of positive BT. Type of antibiotic treatment and clinical response were compiled. Groups of patients with (SIBO⁺) and without SIBO (SIBO^-) were also compared.

Results

A total of 136 patients were included in the study (mean age 51.2, range 20 - 80 years; 63% women), and SIBO was detected in 33.8% (n = 46). Both groups were similar in terms of age, body mass index, and gender. SIBO was significantly associated with the presence of abdominal pain (odds ratio (OR) = 4.78; P < 0.05), bloating (OR = 5.39; P < 0.05), smoking (OR = 6.66; P < 0.05), and anemia (OR = 4.08; P < 0.05). No association was identified with gender, age, obesity, and risk factors for SIBO. Antibiotics were used in 43% of patients with a positive BT, but clinical response was not significantly different in the subgroup that received antibiotics versus the subgroup that did not.

Conclusions

The prevalence of SIBO is high in symptomatic patients who underwent breath testing. Abdominal pain, bloating, smoking, and anemia are strongly associated with SIBO. Treatment of SIBO with antibiotics needs to be further investigated to better determine its efficacy on gastrointestinal symptoms.

Molecular Mechanism Contributing to Malnutrition and Sarcopenia in Patients with Liver Cirrhosis

Liver cirrhosis is frequently accompanied by disease-related malnutrition (DRM) and sarcopenia, defined as loss of skeletal muscle mass and function. DRM and sarcopenia often coexist in cirrhotic patients and are associated with increased morbidity and mortality. The clinical manifestation of both comorbidities are triggered by multifactorial mechanisms including reduced nutrient and energy intake caused by dietary restrictions, anorexia, neuroendocrine deregulation, olfactory and gustatory deficits. Maldigestion and malabsorption due to small intestinal bacterial overgrowth, pancreatic insufficiency or cholestasis may also contribute to DRM and sarcopenia. Decreased protein synthesis and increased protein degradation is the cornerstone mechanism to muscle loss, among others mediated by disease- and inflammation-mediated metabolic changes, hyperammonemia, increased myostatin and reduced human growth hormone. The concise pathophysiological mechanisms and interactions of DRM and sarcopenia in liver cirrhosis are not completely understood. Furthermore, most knowledge in this field are based on experimental models, but only few data in humans exist. This review summarizes known and proposed molecular mechanisms contributing to malnutrition and sarcopenia in liver cirrhosis and highlights remaining knowledge gaps. Since, in the prevention and treatment of DRM and sarcopenia in cirrhotic patients, more research is needed to identify potential biomarkers for diagnosis and development of targeted therapeutic strategies.

Liver Cirrhosis and Sarcopenia from the Viewpoint of Dysbiosis

Sarcopenia in patients with liver cirrhosis (LC) has been attracting much attention these days because of the close linkage to adverse outcomes. LC can be related to secondary sarcopenia due to protein metabolic disorders and energy metabolic disorders. LC is associated with profound alterations in gut microbiota and injuries at the different levels of defensive mechanisms of the intestinal barrier. Dysbiosis refers to a state in which the diversity of gut microbiota is decreased by decreasing the bacterial species and the number of bacteria that compose the gut microbiota. The severe disturbance of intestinal barrier in LC can result in dysbiosis, several bacterial infections, LC-related complications, and sarcopenia. Here in this review, we will summarize the current knowledge of the relationship between sarcopenia and dysbiosis in patients with LC.

Current Status and Prospects of Spontaneous Peritonitis in Patients with Cirrhosis

Spontaneous bacterial peritonitis (SBP) is a common cirrhotic ascites complication which exacerbates the patient's condition. SBP is caused by gram-negative bacilli and, to a lesser extent, gram-positive cocci. Hospital-acquired infections show higher levels of drug-resistant bacteria. Geographical location influences pathogenic bacteria distribution; therefore, different hospitals in the same country record different bacteria strains. Intestinal changes and a weak immune system in patients with liver cirrhosis lead to bacterial translocation thus causing SBP. Early diagnosis and timely treatment are important in SBP management. When the treatment effect is not effective, other rare pathogens should be explored.

Serum and ascitic fluid interleukin-17 in spontaneous bacterial peritonitis in Egyptian patients with HCV-related liver cirrhosis

BACKGROUND

Spontaneous bacterial peritonitis (SBP) is a potentially lethal complication of ascites. The inflammatory response is very intense in case of SBP despite low concentration of bacteria in the ascitic fluid with IL-17A overproduced by intestinal Paneth cells and may have role in host immune defense and inflammatory response.

AIMS

To study the diagnostic performance of serum and ascitic fluid IL-17A as a marker of SBP and its correlation with renal function.

METHODS

120 cirrhotic patients including 80 patients with HCV-induced cirrhotic ascites but not with SBP and 40 patients with HCV-induced cirrhotic ascites with SBP were recruited. Serum and ascitic fluid IL17A were measured before and after treatment.

RESULTS

The mean serum and ascitic fluid levels of IL-17 in cirrhotic patients with SBP were significantly higher than in patients with cirrhosis without SBP (p < 0.001). Also, we found significant decline in both serum and ascitic fluid IL17 levels with successful treatment of SBP (p < 0.001). The sensitivity and specificity of serum IL17 was 100 % when using 92 pg/mL as cutoff. Meanwhile, sensitivity and specificity of ascitic fluid IL-17were 100 % when using 132 pg/mL as cutoff.

CONCLUSIONS

IL-17 could be used as a possible diagnostic biomarker for SBP especially in culture negative and non-neutrocytic SBP and in monitoring therapeutic response. Also, it was shown to be related to hepatic and renal functions deterioration.

Clinical features and outcomes of bacterascites in cirrhotic patients: A retrospective, multicentre study

BACKGROUND & AIMS

Current guidelines on the management of bacterascites are limited. This multicentre, retrospective study investigated the clinical features and outcomes of cirrhosis patients with bacterascites.

METHODS

Two series of cirrhosis patients were evaluated. The first included 418 patients with ascites-positive cultures at 11 hospitals during 2012-2018. Clinical characteristics and outcomes were recorded. The second included 208 patients with sterile ascites from a prospective cohort (NCT02457637). Clinical features and outcomes of cirrhotic patients with or without bacterascites were investigated.

RESULTS

In the first series, bacterascites was diagnosed in 254/418 (60.8%) patients, and culture-positive spontaneous bacterial peritonitis (SBP) in 164/418 (39.2%) patients. Gram-positive bacteria were more prevalent in bacterascites patients than in culture-positive SBP patients (59.1% vs 22.0%; P < .001). For patients with acute-on-chronic liver failure (ACLF) in bacterascites and culture-positive SBP groups, the 28-day transplant-free mortality (41.3% vs 65.5%; P = .015) and the prevalence of in-hospital acute kidney injury (AKI) (84.8% vs 75%; P = .224). For patients without ACLF in the bacterascites (n = 208) and culture-positive SBP groups (n = 108), the 28-day transplant-free mortalities were 13% vs 13.9% (P = .822), the probabilities of progression to ACLF within 28 days were 10.1% vs 14.8% (P = .216) and the prevalences of in-hospital AKI were 14.4% vs 30.6% (P = .001). Bacterascites patients had higher 28-day mortality than those patients with sterile ascites, after propensity score matching (18.4% vs 8.6%; P = .010).

CONCLUSION

Bacterascites patients had non-negligible poor clinical outcomes, including in-hospital AKI, progression to ACLF and 28-day mortality. Future studies are warranted to expedite the diagnosis of bacterascites and optimize antibiotic treatment.

Nonpharmacologic Management of Hepatic Encephalopathy: An Update

Research increasingly shows that the gut-liver-brain axis is a crucial component in the pathophysiology of hepatic encephalopathy (HE). Due to the limitations of current standard-of-care medications, non-pharmacological treatments that target gut dysbiosis, including probiotics, nutritional management, and fecal microbiota transplants, are being considered as alternative and adjunct therapies. Meta-analyses note that probiotics could offer benefits in HE treatment, but have not shown superiority over lactulose. Emerging literature suggests that fecal microbiota transplants could offer a novel strategy to treat gut dysbiosis and favorably impact HE. Finally, liver support devices and liver transplantation could offer a last-resort treatment option for persistent HE.

Gut-Liver Axis and Inflammasome Activation in Cholangiocyte Pathophysiology

The Nlrp3 inflammasome is a multiprotein complex activated by a number of bacterial products or danger signals and is involved in the regulation of inflammatory processes through caspase-1 activation. The Nlrp3 is expressed in immune cells but also in hepatocytes and cholangiocytes, where it appears to be involved in regulation of biliary damage, epithelial barrier integrity and development of fibrosis. Activation of the pathways of innate immunity is crucial in the pathophysiology of hepatobiliary diseases, given the strong link between the gut and the liver. The liver secretes bile acids, which influence the bacterial composition of the gut microbiota and, in turn, are heavily modified by microbial metabolism. Alterations of this balance, as for the development of dysbiosis, may deeply influence the composition of the bacterial products that reach the liver and are able to activate a number of intracellular pathways. This alteration may be particularly important in the pathogenesis of cholangiopathies and, in particular, of primary sclerosing cholangitis, given its strong association with inflammatory bowel disease. In the present review, we summarize current knowledge on the gut–liver axis in cholangiopathies and discuss the role of Nlrp3 inflammasome activation in cholestatic conditions.

Kansuiphorin C and Kansuinin A ameliorate malignant ascites by modulating gut microbiota and related metabolic functions

ETHNOPHARMACOLOGICAL RELEVANCE

Euphorbia kansui is a toxic Chinese herbal medicine and exhibits promising treatment to the malignant ascites (MA) in its traditional use. Ingenane-type and jastrophane-type diterpenes are demonstrated to be responsible for the toxicity and efficacy of kansui. Two representative compounds, kansuiphorin C (KPC) and kansuinin A (KA) in each type were proved to effectively reduce the ascites. The biological and toxicological effects are closely associated with the gastrointestinal tract, but the possible mechanism and related metabolic functions of KPC and KA treating MA through modulating the gut microbiota remain unclear.

AIM OF THE STUDY

To investigate the possible mechanism and related metabolism of KPC and KA ameliorating malignant ascites through modulating gut microbiota.

MATERIALS AND METHODS

MA rats and normal rats were divided into different groups and administrated with KPC, KA, and positive drug, respectively. 16S rDNA gene sequencing and metagenomes analysis combined with the quantification of short-chain fatty acids of feces were performed to reflect the modulation of gut microbiota. Then, the metabolites of KPC and KA in rat feces under the normal and pathological circumstances were detected by ultra-fast liquid chromatography coupled with MS/MS detector (UFLC-MS/MS) to explore the in-vivo bacterial biotransformation.

RESULTS

KPC and KA were modulatory compounds for gut microbiota. The richness of Lactobacillus and the decreased abundance of Helicobacter involved in the carbohydrate metabolism and amino acid metabolism could be responsible for their prohibitory effects on malignant ascites. KPC exhibited stronger modulation of gut microbiota through making the abundance of Helicobacter about 3.5 times lower than KA. Besides, in-vivo microbial biotransformation of KPC and KA contained oxidation, hydrolysis, dehydration, and methylation to form metabolites of lower polarity. Besides, at the dosage of 10 mg kg^-1, the toxicity of both compounds had weaker influences on the gut microbiota of normal rats.

CONCLUSION

KPC and KA could ameliorate malignant ascites by modulating gut microbiota mainly containing the increase of Lactobacillus and the decrease of Helicobacter and related carbohydrate and amino acid metabolism, providing a basis for their promising clinical usage.

Bile microbiota: new insights into biliary complications in liver transplant recipients

Background

Biliary complications represent a major problem associated with liver transplantation. This report represents the first study to use high-throughput 16S ribosomal RNA (rRNA) gene sequencing to assess bile microbiota within bile samples of liver transplant recipients with biliary complications. Our goal in this report was to identify the species and abundance of microbes and examine the potential for microbial involvement of bile in liver transplantation patients with biliary complications.

Methods

Liver transplant recipients treated at our center over the period from September 2015 to June 2017 were enrolled in the study. Patients satisfying the inclusion criteria were divided into two groups, control (N=13) and symptom (N=10). Sequencing of 16s rDNA was then performed on bile samples from both groups.

Results

The main bacterial phyla of bile samples in the symptom group included Proteobacteria (55.19%), Firmicutes (32.36%), Actinobacteria (10.24%) and Bacteroidetes (1.23%) and the main bacterial genera were Pseudomonas (23.31%), Klebsiella (18.42%), Lactococcus (9.61%), Rhodococcus (9.59%) and Rhizobium (5.08%). Proteobacteria and Staphylococcus were enriched in the symptom group (P<0.05), whereas Firmicutes (P<0.05) and Enterococcus (P<0.01) were enriched in the control group. Pathways involved as determined with use of the Kyoto Encyclopedia of Genes and Genomes (KEGG), revealed that metabolism pathways of glyoxylate and dicarboxylate, porphyrin and chlorophyll, arginine and proline, glycine, serine and threonine, as well as the bacterial secretion system were all enriched in bile samples from the symptom group (P<0.05).

Conclusions

Clear differences exist in microbial species distribution in bile samples from the symptom versus control group. The species and pathways enriched in bile samples within the symptom group may be involved in the pathogenesis of biliary complication after liver transplantation.

ACG Clinical Guideline: Small Intestinal Bacterial Overgrowth

Small intestinal bacterial overgrowth is defined as the presence of excessive numbers of bacteria in the small bowel, causing gastrointestinal symptoms. This guideline statement evaluates criteria for diagnosis, defines the optimal methods for diagnostic testing, and summarizes treatment options for small intestinal bacterial overgrowth. This guideline provides an evidence-based evaluation of the literature through the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) process. In instances where the available evidence was not appropriate for a formal GRADE recommendation, key concepts were developed using expert consensus.

Acid suppression therapy and its association with spontaneous bacterial peritonitis incidence: A systemic review and meta-analysis

AIM

It is well known that the use of proton pump inhibitor (PPI) is widespread in patients with liver cirrhosis. PPI counteracts H₂ receptor inhibitor (H₂ RA) with its strong acid suppression effect. However, there is always a concern that PPI use may increase spontaneous bacteria peritonitis (SBP) development in cirrhotic patients. We aimed to investigate the association between acid suppression therapy (i.e. PPI or H₂ RA) and SBP through meta-analysis.

METHODS

We searched PubMed, Medline, Web of Science, Cochrane library, and Embase for relevant studies published up to April 2019. Pooled OR and 95% CI were calculated by a random-effects model. Funnel plots and Egger's tests were performed for the evaluation of publication bias. Non-parametric "trim-and-fill" tests were conducted for sensitivity analysis.

RESULTS

A total of 20 original articles including 9566 cirrhotic patients were analyzed. The overall meta-analysis highlighted that PPI use was associated with the risk of SBP (pooled OR 1.77, 95% CI 1.49-2.11). The conclusion was irrespective of study methods, whereas the result was inconsistent only in South America. However, the conclusion might not be stable enough and should be extrapolated with caution. Unlike PPI, we found H₂ RA was not associated with SBP (pooled OR 1.06, 95% CI 0.75-1.48).

CONCLUSIONS

In conclusion, PPI use, but not H₂ RA, will increase the incidence of SBP in cirrhotic patients. In addition, H₂ RA might be beneficial for patients who require long-term acid suppression therapy.

Diagnosis and management of toxicities of immune checkpoint inhibitors in hepatocellular carcinoma

Immune checkpoint inhibitors (ICIs) have reshaped cancer therapy. ICIs enhance T cell activation through various mechanisms and may help reverse the exhausted phenotype of tumour-infiltrating lymphocytes. However, disrupting the key role that checkpoint molecules play in immune homeostasis may result in autoimmune complications. A broad range of immune-related adverse events (irAEs) involve almost every organ but mostly affect the skin, digestive system, lung, endocrine glands, nervous system, kidney, blood cells, and musculoskeletal system. They are usually manageable but can be life-threatening. The incidence of irAEs is not very different in patients with hepatocellular carcinoma (HCC) compared to other tumour types, although there is a trend towards a higher incidence of hepatic irAEs. HCC usually develops on a background of cirrhosis with associated systemic manifestations. Extrahepatic organ dysfunction in cirrhosis may cause signs and symptoms that overlap with irAEs or increase their severity. Available guidelines for the management of irAEs have not specifically considered the assessment of toxicities in the context of patients with liver cancer and cirrhosis. This review addresses the toxicity profile of ICIs in patients with HCC, focusing on the challenges that the underlying liver disease poses to their diagnosis and management. Challenges include late recognition, inadequate work-up and delayed treatment, overdiagnosis and inappropriate interruption of ICIs, complications caused by immunosuppressive therapy, and increased cost. A specific algorithm for the management of hepatic irAEs is provided.

Intestinal Absorption of Bile Acids in Health and Disease

The intestinal reclamation of bile acids is crucial for the maintenance of their enterohepatic circulation. The majority of bile acids are actively absorbed via specific transport proteins that are highly expressed in the distal ileum. The uptake of bile acids by intestinal epithelial cells modulates the activation of cytosolic and membrane receptors such as the farnesoid X receptor (FXR) and G protein-coupled bile acid receptor 1 (GPBAR1), which has a profound effect on hepatic synthesis of bile acids as well as glucose and lipid metabolism. Extensive research has focused on delineating the processes of bile acid absorption and determining the contribution of dysregulated ileal signaling in the development of intestinal and hepatic disorders. For example, a decrease in the levels of the bile acid-induced ileal hormone FGF15/19 is implicated in bile acid-induced diarrhea (BAD). Conversely, the increase in bile acid absorption with subsequent overload of bile acids could be involved in the pathophysiology of liver and metabolic disorders such as fatty liver diseases and type 2 diabetes mellitus. This review article will attempt to provide a comprehensive overview of the mechanisms involved in the intestinal handling of bile acids, the pathological implications of disrupted intestinal bile acid homeostasis, and the potential therapeutic targets for the treatment of bile acid-related disorders. Published 2020. Compr Physiol 10:21-56, 2020.

The Phylogeny and Biological Function of Gastric Juice-Microbiological Consequences of Removing Gastric Acid

Gastric juice is a unique combination of hydrochloric acid (HCl), lipase, and pepsin. Acidic gastric juice is found in all vertebrates, and its main function is to inactivate microorganisms. The phylogenetic preservation of this energy-consuming and, at times, hazardous function (acid-related diseases) reflects its biological importance. Proton pump inhibitors (PPIs) are one of the most widely used drugs in the world. Due to the reduced prevalence of Helicobacter pylori infection as well as the increased use of inhibitors of gastric acid secretion, the latter has become the most important cause of gastric hypoacidity. In the present manuscript, we review the microbiological consequences of removing gastric acidity. The resulting susceptibility to infections has not been studied extensively, and focus has mainly been restricted to bacterial and parasitic agents only. The strongest evidence concerning the relationship between hypochlorhydria and predisposition to infections relates to bacterial infections affecting the gastrointestinal tract. However, several other clinical settings with increased susceptibility to infections due to inhibited gastric acidity are discussed. We also discuss the impact of hypochlorhydria on the gut microbiome.

Primary and secondary prophylaxis of spontaneous bacterial peritonitis: current state of the art

Introduction: Spontaneous bacterial peritonitis represents a frequent and severe complication in cirrhotic patients with ascites. In daily practice, the diagnosis of spontaneous bacterial peritonitis might be challenging in the absence of the typical signs and symptoms of infection such as fever or leukocytosis. Areas covered: Aim of this review is to revise the current state of the art on primary and secondary spontaneous bacterial peritonitis. Literature search in Medline/Pubmed was performed. Expert opinion: Historically, gram-negative bacteria were the most frequent etiologic agents of spontaneous bacterial peritonitis, with Escherichia coli and Klebsiella spp. being the most frequently isolated bacteria. However, major changes in this regard occurred over the last few decades with an increasing prevalence of gram-positive, quinolone-resistant, and multidrug-resistant bacteria. In particular, the increasing prevalence of quinolone-resistant bacteria challenged the prominent role of norfloxacin in spontaneous bacterial peritonitis prevention. Given the high mortality rate and the risk of developing the hepatorenal syndrome, prophylaxis of spontaneous bacterial peritonitis is indicated in three high-risk populations: patients with acute gastrointestinal hemorrhage, patients with low total protein content in ascitic fluid and advanced cirrhosis, and patients with a previous history of spontaneous bacterial peritonitis (secondary prophylaxis).

Nutrition in Cirrhosis

PURPOSE OF REVIEW

This review discusses the prevalence of malnutrition in cirrhosis, metabolic functions of the liver and alterations in cirrhosis, malnutrition screening tools, and common macronutrient and micronutrient deficiencies encountered in individuals with chronic liver disease and their impact on morbidity and mortality.

RECENT FINDINGS

Several meta-analyses and international society guidelines recommend malnutrition screening and nutrition interventions to improve outcomes in all patients with chronic liver disease given their high risk of malnutrition which is often under recognized. Malnutrition is common in individuals with chronic liver disease and has a significant impact on patient outcomes. Thus, it is critical that validated malnutrition screening tools are used routinely in this patient population in order to identify high-risk patients and implement nutrition and exercise interventions early.

Management of Small Intestinal Bacterial Overgrowth in Adult Patients

The human gastrointestinal tract is a complex system of digestive pathways aided by mechanical processes, enzymes, transport molecules, and colonic bacteria. Occasionally, these bacterial components transplant to atypical locations due to various gastrointestinal imbalances or anatomical structural issues. This may lead to bacterial overgrowth of the small intestine, where minimal or no bacteria are normally found. Symptoms of small intestinal bacterial overgrowth may mimic those of various functional gastrointestinal diseases. Small intestinal bacterial overgrowth is typically diagnosed through hydrogen breath tests or jejunal aspirate culture. Current recommendations indicate antibiotics as the first-line treatment to eradicate or modify the bacterial overgrowth to a more favorable state. Nutritional support is also indicated to correct deficiencies and aid in symptom alleviation. As small intestinal bacterial overgrowth is common in other conditions, much of the research for this area is based on findings in codisease states rather than independent disease research. To provide accurate recommendations for small intestinal bacterial overgrowth, more targeted research is needed.

Dynamic distribution of gallbladder microbiota in rabbit at different ages and health states

The internal environment of the gallbladder has been considered extremely unfavorable for bacterial growth, and the microbial profile of the gallbladder still unknown. By high-throughput sequencing of the bacterial 16S rRNA gene, we studied the microbial profile of the gallbladder from healthy rabbits before and after weaning. Moreover, we investigated the difference of microbiota between the gallbladder and gut. Our results showed that the gallbladder was dominantly populated by Firmicutes, Bacteroidetes, Proteobacteria, and Actinobacteria in the phylum throughout the developmental stages of rabbits. The adult rabbits showed higher species richness and exhibited higher bacterial diversity than rabbits before weaning based on the results of alpha diversity. Beta diversity analyses indicated differences in the bacterial community composition between different developmental stages. In the comparison of the gallbladder and feces, Firmicutes and Bacteroidetes were dominant in the phylum, as they were present in about 61% and 21% of the feces, respectively. Conversely, in the gallbladder, Firmicutes was the most dominant (about 41%), and Bacteroidetes and Proteobacteria were present in about 16% and 22% of the gallbladder, respectively. The Unweighted UniFrac Principal Coordinate Analysis results illustrated samples clustered into 2 categories: the gallbladder and feces. Our study might provide a foundation for knowledge on gallbladder microbiota for the first time and a basis for further studies on gallbladder and intestinal health.

Spontaneous bacterial peritonitis in patients with cirrhosis: incidence, outcomes, and treatment strategies

Spontaneous bacterial peritonitis is the most frequent bacterial infection in patients with cirrhosis. The reported incidence varies between 7% and 30% in hospitalized patients with cirrhosis and ascites, representing one of their main complications. Outcomes in patients with spontaneous bacterial peritonitis are poor since acute kidney injury, acute-on-chronic liver failure, and death occur in as much as 54%, 60%, and 40% of the patients, respectively, at midterm. Early antibiotic treatment of spontaneous bacterial peritonitis is crucial. However, the landscape of microbiological resistance is continuously changing, with an increasing spread of multidrug-resistant organisms that make its current management more challenging. Thus, the selection of the empirical antibiotic treatment should be guided by the severity and location where the infection was acquired, the risk factors for multidrug-resistant organisms, and the available information on the local expected bacteriology. The use of albumin as a complementary therapy for selected high-risk patients with spontaneous bacterial peritonitis is recommended in addition to antibiotics. Even though antibiotic prophylaxis has proven to be effective to prevent spontaneous bacterial peritonitis, a careful selection of high-risk candidates is crucial to avoid antibiotic overuse. In this article we review the pathogenesis, risk factors, and prognosis of spontaneous bacterial peritonitis, as well as the current evidence regarding its treatment and prophylaxis.

Altered Microbiome in Patients With Cirrhosis and Complications

In patients with cirrhosis, the gut microbiome are affected by multiple gut and systemic alterations. These changes lead to dysbiosis in the microbiota of different parts of the body, resulting in inflammation. The constant immune stimulation resulting in part from dysbiosis is associated with morbidity in patients with cirrhosis. Dysbiosis as a dynamic event worsens with decompensation such as with hepatic encephalopathy, infections or acute-on-chronic liver failure (ACLF). These microbial patterns could be applied as diagnostic and prognostic measures in cirrhosis in the outpatient and inpatient setting. Current therapies for cirrhosis have differing impacts on gut microbial composition and functionality. Dietary modifications and the oral cavity have emerged as newer targetable factors to modulate the microbiome, which could affect inflammation and, potentially improve outcomes. Additionally, fecal microbial transplant is being increasingly studied to provide compositional and functional modulation of the microbiome. Ultimately, a combination of targeted therapies may be needed to provide an optimal gut milieu to improve outcomes in cirrhosis.

Small Intestinal Bacterial Overgrowth in Patients With Cirrhosis

Small intestinal bacterial overgrowth (SIBO) is defined by increased density and/or abnormal composition of microbiota in the small bowel. SIBO is often encountered in patients with cirrhosis as a result of impaired intestinal motility and delayed transit time, both of which are exacerbated by more severe liver disease. Additional risk factors for SIBO commonly encountered in cirrhotic patients include coexisting diabetes, autonomic neuropathy, and/or alcoholic use. Diagnosis of SIBO is performed by breath testing or jejunal aspiration, the gold standard. In cirrhotic patients, the presence of SIBO can lead to profound clinical consequences. Increased intestinal permeability in these patients predisposes to bacterial translocation into the systemic circulation. As a result, SIBO is implicated as a significant risk factor in the pathogenesis of both spontaneous bacterial peritonitis and hepatic encephalopathy in cirrhotics. Antibiotics, especially rifaximin, are the best studied and most effective treatment options for SIBO. However, prokinetics, probiotics, nonselective beta-blockers, and treatment of underlying liver-related pathophysiology with transjugular intrahepatic portosystemic shunt placement or liver transplantation are also being investigated. This review will discuss the risk factors, diagnosis, manifestations in cirrhosis, and treatment options of SIBO.