Small intestinal bacterial overgrowth versus antimicrobial capacity in patients with spontaneous bacterial peritonitis

Gut Microbiota and Antibiotic Treatments for the Main Non-Oncologic Hepato-Biliary-Pancreatic Disorders

The gut microbiota is a pivotal actor in the maintenance of the balance in the complex interconnections of hepato-biliary-pancreatic system. It has both metabolic and immunologic functions, with an influence on the homeostasis of the whole organism and on the pathogenesis of a wide range of diseases, from non-neoplastic ones to tumorigenesis. The continuous bidirectional metabolic communication between gut and hepato-pancreatic district, through bile ducts and portal vein, leads to a continuous interaction with translocated bacteria and their products. Chronic liver disease and pancreatic disorders can lead to reduced intestinal motility, decreased bile acid synthesis and intestinal immune dysfunction, determining a compositional and functional imbalance in gut microbiota (dysbiosis), with potentially harmful consequences on the host's health. The modulation of the gut microbiota by antibiotics represents a pioneering challenge with striking future therapeutic opportunities, even in non-infectious diseases. In this setting, antibiotics are aimed at harmonizing gut microbial function and, sometimes, composition. A more targeted and specific approach should be the goal to pursue in the future, tailoring the treatment according to the type of microbiota modulation to be achieved and using combined strategies.

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.

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.

Serum Sphingosine-1-phosphate level and peritonitis in peritoneal dialysis patients

BACKGROUND

Given the important role of Sphingosine-1-phosphate (S1P) in maintaining the hemostasis in intestinal barrier function and regulation of inflammation and immune, we hypothesize that S1P might be a biomarker to predict peritonitis in peritoneal dialysis (PD) patients.

METHODS

In this case-control study, 78 stable, continuous ambulatory peritoneal dialysis patients were enrolled and followed for the episode of PD associated peritonitis. Patients were divided into two groups by whether or not they had peritonitis during follow-up: non-peritonitis (n = 65) and peritonitis (n = 13) group. S1P was analyzed by enzyme-linked immunosorbent assay. Logistic regression analysis was used to assess factors associated with peritonitis. The variables identified by univariable regression models (p < 0.1) were further selected into the multivariable logistic regression model to determine whether they could independently affect peritonitis.

RESULTS

Patients with peritonitis had a lower level of S1P than that of patients without peritonitis (1.3 ng/mL IQ 0.8, 3.6 ng/mL vs. 2.8 ng/mL IQ 1.5, 5.4 ng/mL, p = 0.018). The peritonitis group had lower serum albumin, lower blood leukocyte, lower hemoglobin and lower platelet count as compared to the non-peritonitis group. Logistic regression analysis showed that S1P (OR = 0.381, 95% CI = 0.171-0.848, p = 0.018), blood leukocyte count (OR = 0.438, 95% CI = 0.207-0.925, p = 0.030), and serum albumin (OR = 0.732, 95% CI = 0.556-0.962, p = 0.025) were independent factors associated with peritonitis in the present PD population.

CONCLUSION

Our study showed that S1P was an independent determinant of subsequent peritonitis in PD patients. S1P might serve as a biomarker to predict peritonitis in PD patients.

Use of gastric-acid suppressants may be a risk factor for enteric peritonitis in patients undergoing peritoneal dialysis: A meta-analysis

WHAT IS KNOWN AND OBJECTIVE

Mounting evidence suggests that long-term use of gastric-acid suppressants (GASs) may be associated with adverse effects. Whether GAS use increases the risk of enteric peritonitis in patients undergoing peritoneal dialysis (PD) is not known. The aim of this meta-analysis was to evaluate the association between GAS use and enteric peritonitis in PD patients.

METHODS

We searched PubMed, Embase and Cochrane Library databases from inception to 23 January 2018 to identify eligible studies. The primary outcome was an association between GAS use and enteric peritonitis in PD patients.

RESULTS AND DISCUSSION

Six studies involving 829 people were included in this meta-analysis. Pooled data showed that GAS use in PD patients was associated with an increased risk of enteric peritonitis (odds ratio [OR] = 1.27; 95% confidence interval [CI]: 1.02-1.57, I²  = 48%). Subgroup analyses based on GAS type revealed that histamine-2 receptor antagonists (H₂ RAs) might increase the risk of enteric peritonitis in PD patients (OR = 1.40; 95% CI: 1.01-1.93; I²  = 8%), but proton pump inhibitors (PPIs) might not (1.13; 0.72-1.77; 6; 34%).

WHAT IS NEW AND CONCLUSION

Gastric-acid suppressants use might be a risk factor for enteric peritonitis in PD patients. In particular, H₂ RAs increased the risk of enteric peritonitis, but PPIs did not. Therefore, to prevent enteric peritonitis, H₂ RAs should probably be prescribed with caution for PD patients.

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.

Small intestinal bacterial overgrowth in cirrhosis: systematic review and meta-analysis

BACKGROUND

Small intestinal bacterial overgrowth (SIBO) was detected in cirrhosis in many studies. The aim is to perform a systematic review and meta-analysis on the prevalence of SIBO in cirrhosis and on the relationship of SIBO with features of cirrhosis.

METHODS

PUBMED search (until 14 January 2018) was performed. Specific search terms were: '(cirrhosis) AND (SIBO OR bacterial overgrowth)'. Studies not relating to cirrhosis or SIBO, animal studies, and non-original articles were excluded. A meta-analysis of all studies was performed using a random-effects model.

RESULTS

117 references were identified by the PUBMED search. 3 references were added after handsearching the reference lists of all the articles. 99 references were excluded. 21 studies (included in total 1264 cirrhotics and 306 controls) remained for qualitative analysis and quantitative synthesis. Prevalence of SIBO for cirrhosis was 40.8% (95% CI 34.8-47.1), while the prevalence of SIBO for controls was 10.7% (95% CI 5.7-19.0). OR 6.83 (95% CI 4.16-11.21; p < 0.001). Prevalence of SIBO for decompensated cirrhosis was higher than prevalence of SIBO for compensated cirrhosis (50.5% vs. 31.2%; p < 0.001). SIBO in cirrhosis was associated with ascites (p < 0.001), minimal hepatic encephalopathy (p = 0.001), bacterial translocation (p = 0.026), spontaneous bacterial peritonitis (p = 0.008), prolonged orocecal transit time (p < 0.001), and was not associated with hypocoagulation. Further studies are required to clarify the relationship of SIBO with hyperbilirubinemia, hypoalbuminemia, overt hepatic encephalopathy in past, esophageal varices and systemic inflammation.

CONCLUSION

Small intestinal bacterial overgrowth is more often detected in cirrhosis than in healthy persons and is associated with some features of cirrhosis.

Bacterial translocation in patients with liver cirrhosis: physiology, clinical consequences, and practical implications

The gut liver axis is an operative unit that works to protect the human body against potentially harmful substances and microorganisms, maintaining the homeostasis of the immune system. Liver cirrhosis profoundly alters this complex system. The intestine becomes more permeable allowing the translocation of bacteria, bacterial products and fragments into the portal circulation, triggering an abnormal local and systemic inflammatory response and a condition of perpetual immunologic alarm. This immune-inflammatory disorder related to dysbiosis is involved in the development of liver damage and liver cirrhosis complications and increases intestinal permeability in a vicious circle. Areas covered: The most relevant studies on bacterial translocation, the mechanism of intestinal barrier dysfunction and its consequences in patients with liver cirrhosis have been revised through a PubMed search. Data have been discussed with particular regard to their significance in clinical practice. Expert commentary: The assessment of bacterial translocation and intestinal permeability is not currently used in clinical practice but may be useful to stratify patients' prognosis.

Intestinal permeability in a patient with liver cirrhosis

Liver cirrhosis is a worldwide public health problem, and patients with this disease are at high risk of developing complications, bacterial translocation from the intestinal lumen to the mesenteric nodes, and systemic circulation, resulting in the development of severe complications related to high mortality rate. The intestinal barrier is a structure with a physical and biochemical activity to maintain balance between the external environment, including bacteria and their products, and the internal environment. Patients with liver cirrhosis develop a series of alterations in different components of the intestinal barrier directly associated with the severity of liver disease that finally increased intestinal permeability. A "leaky gut" is an effect produced by damaged intestinal barrier; alterations in the function of tight junction proteins are related to bacterial translocation and their products. Instead, increasing serum proinflammatory cytokines and hemodynamics modification, which results in the appearance of complications of liver cirrhosis such as hepatic encephalopathy, variceal hemorrhage, bacterial spontaneous peritonitis, and hepatorenal syndrome. The intestinal microbiota plays a fundamental role in maintaining the proper function of the intestinal barrier; bacterial overgrowth and dysbiosis are two phenomena often present in people with liver cirrhosis favoring bacterial translocation. Increased intestinal permeability has an important role in the genesis of these complications, and treating it could be the base for prevention and partial treatment of these complications.

Gut microbiota: its role in hepatic encephalopathy

Ammonia, a key factor in the pathogenesis of hepatic encephalopathy (HE), is predominantly derived from urea breakdown by urease producing large intestinal bacteria and from small intestine and kidneys, where the enzyme glutaminases releases ammonia from circulating glutamine. Non-culture techniques like pyrosequencing of bacterial 16S ribosomal ribonucleic acid are used to characterize fecal microbiota. Fecal microbiota in patients with cirrhosis have been shown to alter with increasing Child-Turcotte-Pugh (CTP) and Model for End stage Liver Disease (MELD) scores, and with development of covert or overt HE. Cirrhosis dysbiosis ratio (CDR), the ratio of autochthonous/good bacteria (e.g. Lachnospiraceae, Ruminococcaceae and Clostridiales) to non-autochthonous/pathogenic bacteria (e.g. Enterobacteriaceae and Streptococcaceae), is significantly higher in controls and patients with compensated cirrhosis than patients with decompensated cirrhosis. Although their stool microbiota do not differ, sigmoid colonic mucosal microbiota in liver cirrhosis patients with and without HE, are different. Linkage of pathogenic colonic mucosal bacteria with poor cognition and inflammation suggests that important processes at the mucosal interface, such as bacterial translocation and immune dysfunction, are involved in the pathogenesis of HE. Fecal microbiome composition does not change significantly when HE is treated with lactulose or when HE recurs after lactulose withdrawal. Despite improving cognition and endotoxemia as well as shifting positive correlation of pathogenic bacteria with metabolites, linked to ammonia, aromatic amino acids and oxidative stress, to a negative correlation, rifaximin changes gut microbiome composition only modestly. These observations suggest that the beneficial effects of lactulose and rifaximin could be associated with a change in microbial metabolic function as well as an improvement in dysbiosis.

Protective effect of Bifidobacterium pseudocatenulatum CECT7765 against induced bacterial antigen translocation in experimental cirrhosis

BACKGROUND & AIMS

Intervention in the gut ecosystem is considered as a potential strategy to treat liver diseases and their complications. We have evaluated the effects of Bifidobacterium pseudocatenulatum CECT7765 on bacterial translocation and the liver status in experimental cirrhosis.

ANIMALS & METHODS

Liver damage was induced in Balb/c mice by weight-controlled oral administration of carbon tetrachloride. Laparotomies were performed at week 12. One week prior to laparotomy, animals received B. pseudocatenulatum CECT7765 (10(9) cfu/daily) or placebo intragastrically. All animals received Escherichia coli (10(7) cfu/single dose) intragastrically 24 hours before laparotomy. A group of naïve non-treated animals was included as control. Liver tissue specimens, mesenteric lymph nodes, intestinal content and blood were collected. Liver histology, profibrogenic genes expression, bacterial DNA translocation, serum endotoxaemia and liver cytokine levels were measured.

RESULTS

Bifidobacterium pseudocatenulatum CECT7765 showed no significant effect on structural liver damage, as determined by histological evaluation, alpha-smooth muscle actin distribution, profibrogenic gene expression levels, total hydroxyproline levels and malon dialdehyde production compared with mice receiving placebo. Interestingly, bacterial DNA translocation and serum endotoxin levels were significantly decreased in mice receiving the Bifidobacterium strain compared with placebo. Gut barrier integrity markers were up-regulated in mice receiving B. pseudocatenulatum CECT7765 and quantitatively correlated with intestinal gene copy numbers of the bifidobacterial strain. Gene expression levels of several anti-inflammatory mediators were also increased in mice receiving B. pseudocatenulatum CECT7765 compared with placebo.

CONCLUSION

Oral administration of B. pseudocatenulatum CECT7765 is associated with improved gut barrier integrity and shows a beneficial effect against induced bacterial antigen translocation in the CCl4 -model of cirrhosis.

Homozygous carrier of the NOD2 1007fs frame-shift mutation presenting with refractory community-acquired spontaneous bacterial peritonitis and developing fatal pulmonary mucormycosis: A case report

Genetic variants of the innate immune system contribute to episodes of spontaneous bacterial peritonitis (SBP) in patients with cirrhosis. We herein report the case of a patient with the homozygous nucleotide-binding oligomerization domain containing 2 (NOD2) frame-shift mutation 1007fs presenting with sepsis and community-acquired SBP by Escherichia coli. Secondary peritonitis, pancreatic ascites and malignant causes were excluded by extensive diagnostic work-up. First-line treatment with ceftriaxone was not successful despite in vitro sensitivity of the isolated strain. Despite prolonged second-line treatment with imipenem/cilastatin and intermittent ascites drainage, the ascitic fluid neutrophil count remained markedly elevated in this patient. In the course of the disease the patient developed pneumonia with identification of the typical hyphae of mucormycosis in the bronchoalveolar lavage and died of sepsis with multi-organ failure. On the basis of this observation, variants of the innate immunity have to be considered in therapy-refractory SBP, even when they are community-acquired and caused by cephalosporin-sensitive Enterobacteriaceae.

Frequency and factors associated with small intestinal bacterial overgrowth in patients with cirrhosis of the liver and extra hepatic portal venous obstruction

Spontaneous bacterial peritonitis (SBP), a common complication of cirrhosis of liver, might result from translocation of bacteria from the small bowel. However, there is scanty data on frequency of small intestinal bacterial overgrowth (SIBO) in patients with cirrhosis of the liver. There are no data on SIBO in patients with extra-hepatic portal venous obstruction (EHPVO) in the literature. A total of 174 patients with cirrhosis of the liver, 28 with EHPVO and 51 healthy controls were studied for SIBO using glucose hydrogen breath test (GHBT). Persistent rise in breath hydrogen 12 ppm above basal (at least two readings) was considered diagnostic of SIBO. Of 174 patients (age 47.2 +/- 11.9 years, 80.5% male) with cirrhosis due to various causes, 67 (38.5%) were in Child's class A, 70 (40.2%) class B and 37 (21.7%) class C. Of the 174 patients with cirrhosis, 42 (24.14%) had SIBO as compared to 1 of 51 (1.9%) healthy controls (P < 0.0001). Patients with EHPVO had similar frequency of SIBO compared to healthy controls [2/28 (7.14%) vs 1/51 (1.97%), P = ns]. Frequency of SIBO in Child's A, B and C was comparable [13 (18.6%) vs 16 (23.9%) and 13 (35.1%), respectively; P = ns]. Presence of SIBO were not related to ascites, etiology of cirrhosis, and degree of liver dysfunction. SIBO is common in patients with cirrhosis of the liver. Patients with EHPVO do not have higher frequency of SIBO than healthy subjects. SIBO in cirrhosis is not related to the degree of derangement in liver function or of portal hypertension.

Hypokalaemia: an independent risk factor of Enterobacteriaceae peritonitis in CAPD patients

BACKGROUND

Hypokalaemia is a relatively common complication in uraemic patients undergoing continuous ambulatory peritoneal dialysis (CAPD). The hazards of hypokalaemia are multiple and have been correlated with patient morbidity and mortality. Whether it is associated with increased risk of peritonitis remains to be addressed.

METHODS

We retrospectively analysed our CAPD patients who had complicating peritonitis in a 2-year period. The influence of hypokalaemia on the clinical features of peritonitis was assessed. From September 2003 to August 2005, 140 unselected patients undergoing CAPD treatment and followed up in our hospital were recruited for the study. Hypokalaemia was defined as a serum potassium level <3.5 mmol/l. The impact of hypokalaemia on several clinical parameters, including the nutrition status, dialysis adequacy, occurrence of peritonitis and the etiologic pathogens, was analysed.

RESULTS

During the study period, 462 determinations (23.6%) were below quantity <mmol/l. The overall peritonitis rate was 30.6 patient-month per episode (total 64 episodes). The prevalence of peritonitis was significantly higher in patients with hypokalaemia (6.9%) compared to those without hypokalaemia (2.1%, P < 0.001). Hypokalaemia was also associated with lower serum albumin (P < 0.001), serum phosphate (P < 0.001), total serum cholesterol (P = 0.049) and normalized protein nitrogen appearance (P < 0.001). There was no correlation between serum potassium level and daily PD exchange volume, total Kt/V, urine volume or daily ultrafiltration volume. The peritoneal equilibration test was not significantly different between patients with and without hypokalaemia. When the aetiologic organisms of peritonitis were grouped according to their usual site of colonization, Enterobacteriaceae appeared to be much more prevalent than epidermal microorganisms (53.1% versus 18.8%, P = 0.004) in the hypokalaemia group. However, this was not the case in patients with normal serum potassium.

CONCLUSION

CAPD patients with hypokalaemia are associated with a higher prevalence of peritonitis and poor nutritional status. Enterobacteriaceae were the predominant organisms causing peritonitis in the group with hypokalaemia. This unique and novel finding implies the translocation of these organisms from intestinal mucosa into the peritoneal cavity. A pathogenic mechanism linking malnutrition and hypokalaemia is also proposed.

Intestinal bacterial overgrowth in CAPD patients with hypokalaemia

OBJECTIVE

We have previously demonstrated that hypokalaemia is a risk factor for enteric peritonitis in CAPD patients. The underlying mechanism is unclear, and there have been no similar reports. We hypothesized that hypokalaemia may result in dysmotility of the intestinal tract and in turn cause bacterial overgrowth and subclinical translocation of enteral bacteria.

METHODS

Uraemic patients undergoing CAPD in our hospital were enrolled in the study. Hypokalaemia was defined as a serum potassium (K) level < or = 3.5 mEq/L despite treatment for 1 month. A breath hydrogen test (BHT) was performed to detect if intestinal bacterial overgrowth was present. Blood samples were also collected for the study of inflammatory cytokines, including interleukin 1 (IL1), IL2, IL6, IL8, TNF-alpha and gamma-IFN.

RESULTS

A total of 68 patients were recruited. Hypokalaemia was present in 18 cases (26.5%, group 1), while 50 cases (group 2) had normal serum K levels. A higher prevalence of abnormal BHT was found in group 1 (27.8%), compared with group 2 (8.0%, P = 0.048). There was a trend towards a higher prevalence of abnormal BHT in diabetes mellitus (DM) patients with hypokalaemia (80.0%) compared with normal kalaemia (22.2%, P = 0.09), while no similar trends were found in non-DM hypokalaemic patients (7.7 versus 4.9%). When comparisons were made among different subgroups, patients with DM and hypokalaemia had a significantly higher prevalence of abnormal BHT compared to non-DM, normokalaemic patients (P < 0.0004) and non-DM, hypokalaemic patients (P = 0.008). Multivariate logistic regression analysis revealed that DM was an independent risk factor for abnormal BHT (odds ratio: 12.39, 95% CI: 2.25-68.20, P = 0.004). There was no significant difference in serum albumin, Kt/V, weekly creatinine clearance, pattern of peritoneal equilibrium test, C-reactive protein and various inflammatory cytokines between the two groups.

CONCLUSION

CAPD patients with hypokalaemia may have intestinal bacterial overgrowth. While both DM and hypokalaemia might contribute to this abnormality, only DM appeared to be the independent risk factor.

Probiotics and prebiotics — renaissance of a therapeutic principle

Probiotics are nonpathogenic microorganisms mostly of human origin which, when administered in adequate amounts, confer a health benefit on the host and enable to prevent or improve some diseases. Probiotics may be a natural temporary constituent of the resident intestinal microflora, but their concentration is not sufficient for therapeutic purposes. The microbiota, the intestinal epithelium, and the mucosal immune system constitute the gastrointestinal ecosystem. All three components are essential for complete functional and developmental maturity of the system. The viability of intestinal microflora (including probiotic strains) requires the availability of nutritional substrates (prebiotics), i.e. various types of fiber and oligosaccharides. Prebiotics are cleaved by microbial enzymes to numerous substances (short-chain fatty acids, aminoacids, polyamines, growth factors, vitamins and antioxidants) indispensable for metabolic and functional activities of the intestinal mucosa. The principal probiotics in use include lactobacilli, bifidobacteria, some nonpathogenic strains of Escherichia coli, and Saccharomyces boulardii. These microbiota display favourable effects which qualify them for therapeutic use. For this purpose, probiotics have to fulfill a series of requirements verifying their efficacy and safety. Experimental and clinical studies examine the prerequisites for the administration of probiotics in digestive diseases, allergic and atopic affections, as well as in some extraintestinal conditions. Future goals of probiotic application include genomic analysis, controlled postnatal colonisation of the digestive tract, the use of probiotics as carriers of peroral vaccines, and recombinant probiotics with in-situ production and targeted application of therapeutic molecules.

Intestinal mucosal alterations in rats with carbon tetrachloride-induced cirrhosis: changes in glycosylation and luminal bacteria

Spontaneous bacterial peritonitis is a major cause of mortality after liver cirrhosis. Altered permeability of the mucosa and deficiencies in host immune defenses through bacterial translocation from the intestine due to intestinal bacterial overgrowth have been implicated in the development of this complication. Molecular mechanisms underlying the process are not well known. In order to understand mechanisms involved in translocation of bacteria, this study explored the role of oxidative stress in mediating changes in intestinal mucosal glycosylation and luminal bacterial content during cirrhosis. CCl4-induced cirrhosis in rats led to prolonged oxidative stress in the intestine, accompanied by increased sugar content of both intestinal brush border and surfactant layers. This was accompanied by changes in bacterial flora in the gut, which showed increased hydrophobicity and adherence to the mucosa. Inhibition of xanthine oxidase using sodium tungstate or antioxidant supplementation using vitamin E reversed the oxidative stress, changes in brush border membrane sugar content, and bacterial adherence. In conclusion, oxidative stress in the intestine during cirrhosis alters mucosal glycosylation, accompanied by an increased hydrophobicity of luminal bacteria, enabling increased bacterial adherence onto epithelial cells. This might facilitate translocation across the mucosa, resulting in complications such as spontaneous bacterial peritonitis.

Tumor necrosis factor-alpha induces apoptosis of enterocytes in mice with fulminant hepatic failure

AIM: To explore the alterations of intestinal mucosa morphology, and the effects of tumor necrosis factor α (TNFα) on enterocyte apoptosis in mice with fulminant hepatic failure (FHF).

METHODS: Liver damage was induced by lipopolysaccharide (LPS)/TNF-α in D-galactosamine (GalN) sensitized BALB/c mice. There were 40 mice in normal saline (NS)-treated group, 40 mice in LPS-treated group, 40 mice in GalN-treated group, 120 mice in GalN/ LPS-treated group and 120 mice in GalN/ TNFα-treated group. Each group was divided into five subgroups of eight mice each. Serum samples and liver, intestinal tissues were respectively obtained at 2, 6, 9, 12 and 24 h after administration. Anti-TNFα monoclonal antibody was injected intravenously into GalN/LPS-treated mice. Serum TNFα levels were determined by enzyme-linked immunosorbent assays (ELISA). Serum ALT levels were determined using an automatic analyzer. The intestinal tissues were studied under light microscope and electron microscope at 2, 6, 9, 12 and 24 h in mice with fulminant hepatic failure, respectively. Enterocyte apoptosis was determined by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) method. The expression of tumor necrosis factor receptor 1 (TNFR1) in intestinal tissue was tested by immunohistochemistry Envision Two Steps.

RESULTS: Gut mucosa was morphologically normal at all time points in all groups, but typical apoptotic cells could be seen in all experimental groups under electron micro-scope. Apoptosis rate of gut mucosal epithelial cells were significantly increased at 6, 9 and 12 h, peaked at 12 h in mice with fulminant hepatic failure. TNFα induced apoptosis of enterocytes in mice with FHF. The integrated OD (IOD) levels of TNFα receptor 1 protein expressed in the intestine of mice with GalN/LPS and GalN/ TNFα-induced FHF at 2, 6, 9, 12 and 24 h after GalN/LPS and GalN/TNFα administration were 169.54±52.62/905.79±111.84, 11350.67±2133.26/28160.37±4601.67, 25781.00±2277.75/122352.30±49412.40, 5241.53±3007.24/49157.93±9804.88, 7086.13±1031.15/3283.45±127.67, respectively, compared with those in control groups (with NS, LPS and GalN administration, respectively). IOD level of TNFR1 changed significantly at 6, 9 and 12 h after GalN/LPS and GalN/TNFα administration. The expression of TNFR1 protein was significantly higher at 9 h after GalN/LPS and GalN/TNFα administration than that in control groups. Protein expression of TNFR1 was positively correlated with enterocyte apoptosis.

CONCLUSION: TNFα can induce apoptosis of enterocytes in mice with FHF. Anti-TNFα IgG can inhibit this role.

Nitric oxide and the hyperdynamic circulation in cirrhosis: is there a role for selective intestinal decontamination?

Abnormal vascular tone is responsible for many of the complications seen in cirrhosis making the identification of the pathophysiology of abnormal dilatation a major focus in hepatology research. The study of abnormal vascular tone is complicated by the multiple vascular beds involved (hepatic, splanchnic, peripheral, renal and pulmonary), the differences in the underlying cause of portal hypertension (hepatic versus pre-hepatic) and the slow evolution of the hyperdynamic state. The autonomic nervous system, circulating vasodilators and abnormalities in vascular smooth muscle cells (receptors, ion channels, signalling systems and contraction) have all been implicated. There is overwhelming evidence for an overproduction of NO (nitric oxide) contributing to the peripheral dilatation in both animal models of, and in humans with, cirrhosis and portal hypertension. This review focuses on the proposal that endotoxaemia, possibly from gut-derived bacterial translocation, causes induction of NOS (NO synthase) leading to increased vascular NO production, which is the primary stimulus for the development of vasodilatation in cirrhosis and its accompanying clinical manifestations. The current controversy lies not in whether NO production is elevated, but in which isoform of NOS is responsible. We review the evidence for endotoxaemia in cirrhosis and the factors contributing to gut-derived bacterial translocation, including intestinal motility and permeability, and finally discuss the possible role of selective intestinal decontamination in the management of circulatory abnormalities in cirrhosis.

Effect of TNF-α on tight junctions between the epithelial cells of intestinal mucosal barrier

AIM: To investigate the effect of TNF-α on tight junctions between the epithelial cells of the intestinal mucosal barrier.

METHODS: Colon cancer cell line (CaCo-2) was cultured. The localizations of zonula occluden-1 (ZO-1) in CaCo-2 epithelial cells were detected by immunofluorescence after exposure to TNF-α (0, 50, 100 and 200 mg/L) for 24 h and the TNF-α treatment with 100 mg/L for 0, 4, 8 and 24 h. The expression level of ZO-1 was analyzed by semi-quantitative reverse transcriptase-PCR after exposure to TNF-α with the above time and concentration.

RESULTS: Different expression levels of ZO-1 depended on different time and concentration of TNF-α treated on CaCo-2 epithelial cells. The integrity of tight junctions was disrupted and the expression level of ZO-1 decreased after treatment with TNF-α. The intensity of the immunofluorescent signal was less intensive after exposure to TNF-α 100 and 200 mg/L than that to 0 and 50 mg/L. The intensity of the immunofluorescent signal was less intensive after exposure to TNF-α 100 mg/L for 24 hours than those for 0 h, 4 h and 8 h. The RT-PCR results showed that after CaCo-2 cells were treated for 24h with the indicated concentrations (0, 50, 100 and 200 mg/L) of TNF-α and the TNF-α treatment with 100 mg/L for 0 h, 4 h, 8 h and 24 h, the expression levels of ZO-1 mRNA in CaCo-2 cells were decreased by TNF-α with 100 mg/L for 24 h, as compared with control (P < 0.01).

CONCLUSION: Tight junctions between the epithelial cells of the intestinal mucosal barrier can be destroyed by TNF-α, and decreased expression level of ZO-1 induced by TNF-α is one of the most important molecular mechanisms.

Non-Life-Threatening Sepsis: Report of Two Cases

Streptococcus bovis is one of the nonenterococcal species included among the streptococci group D. It is part of the normal bowel flora in humans and animals, but it is also responsible for infectious diseases (10-15% of all cases of bacterial endocarditis). Many cases of bacteremia and metastatic abscesses (spleen, liver, soft tissues, bone, meninges, endocardium) caused by S. bovis were reported as associated with digestive tract diseases, mainly colonic disease, and, in particular colonic neoplasms, or chronic liver diseases. A role in carcinogenesis has been suggested for this microorganism. The authors report two cases of S. bovis sepsis, one associated with colonic neoplasm and the other with liver cirrhosis and gastric carcinoma. Discussion is focused on probable mechanisms that favor gastric colonization and systemic diffusion of S. bovis from the gut in patients with gastrointestinal neoplasms or chronic liver disease and provides clinical recommendations for patients with S. bovis infections.

Treatment of ascites

Ascites is the most common complication of cirrhosis and occurs in more than half of all patients with cirrhosis. The development of ascites indicates progression of the underlying cirrhosis and is associated with a 50% 2-year survival rate. Conventional therapies used for the treatment of ascites include sodium restriction (<88 mmol/d), diuretics, and large volume paracentesis (LVP) (>5 L). The most effective diuretic combination is that of a potassium-sparing, distal-acting diuretic (eg, spironolactone) with a loop diuretic (eg, furosemide). LVP provides rapid resolution of symptoms with minimal complications and is well tolerated by most patients. Post-paracentesis circulatory dysfunction (PPCD) may occur after LVP and is characterized by hyponatremia, azotemia, and an increase in plasma renin activity. PPCD is associated with an increased mortality and may be prevented by administration of albumin intravenously (6 to 8 g/L of ascites removed) along with LVP. The development of either diuretic-resistant or diuretic-intractable ascites occurs in approximately 5% to 10 % of all cases of ascites. This is a poor prognostic sign, as 50% of such patients die within 6 months of its development. The only definitive therapy for refractory ascites with cirrhosis is orthotopic liver transplantation. The other options that are available include LVP, peritoneovenous shunts, and transjugular intrahepatic portosystemic shunts (TIPS). The TIPS procedure has not been shown to have any influence on survival in patients with cirrhosis and refractory ascites, and TIPS is contraindicated in patients who have advanced liver failure because it can hasten death in such individuals. Peritoneovenous shunts are associated with a high incidence of complications and frequent occlusion. They are, therefore, rarely used for refractory ascites. Spontaneous bacterial peritonitis (SBP) is a common complication of cirrhotic ascites. It may precipitate hepatorenal syndrome. The overall mortality rate from an episode of SBP is approximately 20%. Following an episode of SBP, the 1-year mortality rate approaches 70%. Hospitalized patients should be treated with intravenous third-generation cephalosporins (eg, cefotaxime), and patients at risk should receive prophylaxis with either orally administered quinolones (eg, norfloxacin) or cotrimoxazole.

Why do bacteria reach ascitic fluid?

Spontaneous bacterial peritonitis (SBP) is the most common and serious infection that develops in cirrhotic patients. Translocation of bacteria from their intestinal origin, alterations in immune defence mechanisms and deficiencies in the ascitic fluid antimicrobial activity seem to represent the main steps in the pathogenesis of SBP in cirrhosis. Among the factors determining the development of bacterial translocation, intestinal bacterial overgrowth (mainly related to decreased intestinal motility) and changes in the intestinal barrier appear to play an outstanding role. In conclusion, greater understanding of the pathogenesis of SBP will allow better identification of patients at high risk of developing this complication and contribute to the search for new strategies for its prevention.

Ascites

Ascites is the most common presentation of decompensated cirrhosis, and its development heralds a poor prognosis, with a 50% 2-year survival rate. Effective first-line therapy for ascites includes sodium restriction (2 g/d), use of diuretics, and large-volume paracentesis (LVP). Ideally, a combination of a loop-acting diuretic (eg, furosemide) and a distal-acting diuretic (eg, spironolactone) is used. LVP has the advantage of producing immediate relief from ascites and its associated symptoms. When 5 L or more ascitic fluid is removed, albumin (6 to 8 g per liter of fluid removed) should be administered intravenously to minimize hemodynamic and renal dysfunction. The development of refractory ascites is particularly ominous, and 50% of such patients die within 6 months of its development. Liver transplantation is the only effective therapy for patients with refractory ascites associated with cirrhosis; unfortunately, this therapy is not available for many of those with refractory ascites. Other therapies that are available include LVP, peritoneovenous shunts, and transjugular intrahepatic portasystemic shunts (TIPS). LVP alleviates ascites rapidly, but ascites recurs universally, requiring repeated hospitalizations and paracenteses and decreasing patient quality of life. Peritoneovenous shunts rarely are used due to their high complication rate and tendency to become occluded. Recently, the use of TIPS has been shown to be an effective therapy for patients with refractory ascites. It is most effective when liver function is relatively well preserved. On the other hand, TIPS may hasten death in those with advanced liver failure. TIPS has not been shown to have a clear-cut beneficial effect on survival in patients with refractory ascites. Spontaneous bacterial peritonitis is the most common complication of ascites and is associated with a worsening hyperdynamic circulation and a mortality rate of approximately 20%. Following an episode of spontaneous bacterial peritonitis, the 1-year mortality rate approaches 70%. Patients at risk should be considered for prophylaxis with an orally administered quinolone (eg, norfloxacin). Alternatives include trimethoprim/sulfamethoxazole. Active spontaneous bacterial peritonitis should be treated with an intravenously administered third-generation cephalosporins (eg, cefotaxime) in most circumstances.