The prevalence of gut translocation in humans

[Physiopathology of bacterial translocation and spontaneous bacterial peritonitis in cirrhosis]

The key pathogenic mechanism initiating spontaneous bacterial peritonitis (SBP) is bacterial translocation (BT), a process through which enteric bacteria cross the intestinal barrier and infect the mesenteric lymph nodes, thus entering the blood circulation and ascitic fluid. The high rate of bacterial translocation in cirrhosis is due to injury to the three pilars composing the intestinal mucosal barrier (the balance of intraluminal bacterial flora, the integrity of the intestinal epithelial barrier, and the local immune system). Blood dissemination and microbial growth in ascitic fluid resulting from SBP are a consequence of damage to the immune system in cirrhosis. Hyperproduction of proinflammatory cytokines and other vasoactive substances contributes to the arterial vasodilation and renal failure that frequently complicate the course of SBP. Even in the absence of SBP, translocation of bacteria and bacterial products from the intestinal lumen contribute to systemic inactivation of immune cells in cirrhosis.

Review article: bacterial translocation in the critically ill--evidence and methods of prevention

BACKGROUND

Delayed sepsis, systemic inflammatory response syndrome (SIRS) and multiorgan failure remain major causes of morbidity and mortality on intensive care units. One factor thought to be important in the aetiology of SIRS is failure of the intestinal barrier resulting in bacterial translocation and subsequent sepsis.

AIM

This review summarizes the current knowledge about bacterial translocation and methods to prevent it.

METHODS

Relevant studies during 1966-2006 were identified from a literature search. Factors, which detrimentally affect intestinal barrier function, are discussed, as are methods that may attenuate bacterial translocation in the critically ill patient.

RESULTS

Methodological problems in confirming bacterial translocation have restricted investigations to patients undergoing laparotomy. There are only limited data available relating to specific interventions that might preserve intestinal barrier function or limit bacterial translocation in the intensive care setting. These can be categorized broadly into pre-epithelial, epithelial and post-epithelial interventions.

CONCLUSIONS

A better understanding of factors that influence translocation could result in the implementation of interventions which contribute to improved patient outcomes. Glutamine supplementation, targeted nutritional intervention, maintaining splanchnic flow, the judicious use of antibiotics and directed selective gut decontamination regimens hold some promise of limiting bacterial translocation. Further research is required.

Bacterial translocation: overview of mechanisms and clinical impact

Bacterial translocation (BT) is a phenomenon in which live bacteria or its products cross the intestinal barrier. Gut translocation of bacteria has been shown in both animal and human studies. BT and its complications have been shown clearly to occur in animal models, but its existence and importance in humans has been difficult to ascertain. We review the mechanisms of BT and its clinical impact based on the current literature.

Bacterial translocation may influence the long-term survival in colorectal cancer patients

PURPOSE

The purpose of this study was to investigate the association of bacterial translocation with long-term disease-specific and disease-free survival in colorectal cancer patients.

METHODS

This was a prospective cohort study in which 128 and 30 colorectal cancer patients undergoing curative and palliative resections, respectively, were recruited between 1992 and 1997. Samples of mesenteric lymph nodes were harvested for culture before administration of prophylactic antibiotics. Median follow-up for patients without cancer death was 103 (range, 72-147) months. This cohort of patients was internally validated by Dukes staging.

RESULTS

The cumulative disease-specific survival (time to death) and disease-free survival (time to recurrence) for all patients at five years of follow-up was 55 percent (standard error [SE], 4.4 percent) and 65 percent (SE, 4.8 percent), respectively. Bacteria were isolated from the mesenteric nodes of 23 (15 percent) patients. There was no association between bacterial translocation and nodal metastases, bowel obstruction, and septic complications. Patients with confirmed bacterial translocation had a worse disease-specific survival (n=158, 5-year survivorship estimates+/-SE, 38 percent+/-12 percent vs. 58 percent+/-4.7 percent; P < 0.01) and disease-free survival (n=128, 5-year survivorship estimates+/-SE, 46 percent+/-14 percent vs. 66 percent+/-5 percent; P = 0.004) than those without. Using multivariate Cox regression analysis, bacterial translocation was a predictor of disease-specific survival (P = 0.011) and disease-free survival (P = 0.02) independent of other pathologic prognostic indicators.

CONCLUSION

Colorectal cancer patients with bacterial translocation in the mesenteric lymph nodes have a worse outcome.

Commensal bacteria do translocate across the intestinal barrier in surgical patients

BACKGROUND

The "gut origin of sepsis" hypothesis proposes that enteric bacteria may cause sepsis at distant extra-intestinal sites. Whilst there is much circumstantial evidence to support this hypothesis, there is no conclusive proof in humans. The nature of translocating bacteria remains unclear. The aim of this study was to establish the origin of Escherichia coli (E. coli) cultured from mesenteric lymph nodes (MLN) and determine if they belonged to any recognized pathotypes known to cause infections in humans.

METHODS

MLN and faecal samples were obtained from 98 patients undergoing colonic resection. E. coli were isolated from 9/98 MLN samples. DNA fingerprints of MLN isolates were compared with faecal isolates from the same patient. MLN isolates were tested for adherence and invasion using HEp-2 epithelial cells, and screened for DNA markers indicative of different pathotypes of E. coli. MLN isolates were also tested for internalisation into Caco-2 cells.

RESULTS

All the nine E. coli cultured from MLNs were found to have identical DNA fingerprints to at least one and often several E. coli isolates cultured from faecal samples of the same patient. 8/9 (89%) MLN isolates were weakly adherent and 2/9 (22.2%) were invasive. 8/9 (89%) tested negative for DNA markers. All the nine MLN strains were internalised by Caco-2 cells.

CONCLUSION

This study confirms the gut origin of translocating bacteria. Most translocating E. coli do not belong to any recognised pathotype and are therefore normal commensal microflora. Our results suggest that bacterial translocation is more dependent upon the gut epithelium rather than the virulence properties of resident enteric bacteria.

Protective effects of nafamostat mesilate on liver injury induced by lipopolysaccharide in rats: possible involvement of CD14 and TLR-4 downregulation on Kupffer cells

Nafamostat mesilate (NM) is a synthetic protease inhibitor with various biological effects. To determine its effect on liver injury related to sepsis, we investigated the effects of NM on lipopolysaccharide (LPS)-induced liver injury. Wistar rats were allocated into two groups; the NM group underwent intraperitoneal NM administration 30 min before LPS administration, and the control group underwent PBS administration. Serum AST and ALT levels were significantly decreased in NM-treated rats. Reduced levels of TNF-alpha, IL-1beta, and IFN-gamma were observed after LPS administration in NM-treated rats. No significant differences were observed in IL-6 levels between the NM and the control group. In contrast, HGF levels were significantly increased only in control rats. NM treatment decreased protein and mRNA levels of TLR-4 and CD14. Our data suggest that NM treatment has protective effects against LPS-induced hepatotoxicity through downregulation of TLR4 and CD14 in liver, which decreased TNF-alpha, IL-1beta, and IFN-gammaproduction in liver.

Risks and benefits of nutritional support during critical illness

Critically ill patients who depend on intensive care for more than a few days reveal profound erosion of lean body mass, which is thought to contribute to high morbidity and mortality. Despite a shortfall of evidence that supplemental feeding actually alters clinical outcome of these life-threatening disease states, this observation evoked an almost universal, albeit often inappropriate, use of nutritional support (NS) in the critically ill, administered via the parenteral or the enteral route. Lack of knowledge and overenthusiasm subsequently resulted in complications associated with both parenteral nutrition (PN) and enteral nutrition (EN), which led to the standing controversy over which should be preferred. With time, however, it became clear that EN and PN are not mutually exclusive and that critically ill patients requiring NS should be fed according to the functional status of the gastrointestinal tract. In addition, tight blood glucose control with insulin is advised in fed critically ill patients because overall metabolic control appears to surpass any outcome benefit attributed to the route of feeding. Recently, various special nutritional formulas have been suggested to prevent or treat multiorgan failure in the critically ill, among other pathways via modulation of immune function. Although special nutritional formulas may be promising in a variety of clinical settings, based on currently available data, these cannot be recommended for routine use in critically ill patients.

Surgical manipulation of the large intestine increases bacterial translocation in patients undergoing elective colorectal surgery

OBJECTIVE

Several animal studies have suggested that surgical manipulation of the intestine alters the barrier function and promotes bacterial translocation (BT). Whether this occurs in humans has never been investigated. The aim of this study was to determine the effect of surgical manipulation of the intestine on the prevalence of BT in patients undergoing elective colorectal surgery.

METHOD

This was a prospective observational study of 50 consecutive elective surgical patients in whom a sample of mesenteric lymph node (MLN) was harvested after mobilization of the colon, prior to ligation of the vascular pedicle. These results were compared with 472 historical controls, who had a sample of MLN taken before the mobilization of colon during laparotomy. A positive culture of MLN confirmed BT.

RESULTS

BT was identified in 39/49 (79.6%) patients in the study group compared with 54/472 (11.4%) patients in the control group. This difference was statistically significant (P < 0.001, chi(2) test).

CONCLUSION

Surgical manipulation of the bowel does increase the prevalence of BT and therefore is associated with changes in gut barrier function in elective surgical patients.

Evaluation of intestinal mucosal permeability function in patients with acute pancreatitis

This study aims to evaluate the intestinal mucosal permeability in patients with acute pancreatitis. The lactulose:mannitol (L:M) ratio was used to assess permeability. It is an inexpensive and quite reliable method. The intestinal permeability was increased in patients with acute pancreatitis compared with the controls. In addition, patients with severe pancreatitis had higher intestinal barrier dysfunction compared with patients with mild pancreatitis, the L:M ratio being .2 and .029, respectively. It was also concluded that the permeability increased gradually over the course of pancreatitis and was maximum at day 7 (P < .01). This provides a window of opportunity for therapeutic intervention to prevent the late observed increase in intestinal permeability.

Bacterial translocation as a source of Dacron-graft contamination in experimental aortic operation: the importance of controlling SIRS

BACKGROUND

Several experimental studies have shown the beneficial effects of nitric oxide (NO) in the modulation of the systemic inflammatory response syndrome (SIRS). Nitric oxide is involved in and affects almost all stages in the development of inflammation. We have attempted to ascertain whether the nitric oxide donor molsidomine prevents aortic graft contamination through control of the SIRS and a decrease in bacterial translocation (BT).

METHODS

Twenty-four mini-pigs were divided into 4 groups. The animals were subjected to suprarenal aortic/iliac cross-clamping (for 30 minutes) and by-pass with a Dacron-collagen prosthetic graft impregnated in rifampicin. Groups: 1) sham (aortic dissection alone); 2) cross-clamping and bypass; 3) hemorrhage of 40% of total blood volume before cross-clamping and by-pass; and 4) the same as in group 3 but also including the administration of the NO donor molsidomine (4 mg/kg) 5 minutes before cross-clamping.

VARIABLES

1) bacteriology of mesenteric lymph nodes (MLN), kidney, blood, and prosthesis; 2) serum TNF-alpha (ELISA); and 3) iNOS expression in kidney and liver (Western blot).

RESULTS

Aortic cross-clamping with or without hemorrhage was associated with BT in 80% and 100% of the animals, respectively. About 86% of the bacteria isolated in the graft were also present in MLN. This contamination coincided with an increase in TNF-alpha and with a greater expression of iNOS. Molsidomine administration decreased TNF-alpha and iNOS, decreased BT (from 100% to 20% of the animals), and decreased graft contamination (from 83% to 20%).

CONCLUSIONS

The present model induces high levels of BT and SIRS, both acted as sources of contamination for the implanted Dacron graft. Molsidomine administration decreased the presence of bacteria in the graft by controlling BT and modulating SIRS.

The management of suspected pancreatic sepsis

The management of infected pancreatic necrosis is centered on image-guided fine needle aspiration followed by antibiotic therapy that is based on microbiologic culture results. The authors favor targeted antibiotic therapy rather than routine prophylactic antibiotic coverage. Prompt surgical debridement is recommended for patients who have infected necrosis who are suitable operative candidates. Newer surgical, percutaneous, and endoscopic techniques, as well as prolonged antibiotic therapy without intervention, are being evaluated as alternatives to operative debridement. Well-designed prospective trials will help to determine optimal treatment for patients who have infected pancreatic necrosis.

Early internal fracture fixation prevents bacterial translocation

The aim of our study was to determine whether early internal fixation of major bone fractures helps prevent bacterial translocation in patients with multitrauma. Thirty-seven Sprague-Dawley rats were divided into three groups: (1) anesthesia only (n = 12); (2) the trauma group: tibia and femur fractures and moderate head trauma under anesthesia (n = 14); and (3) the fixation group: fixation of tibia and femur fractures and moderate head trauma under anesthesia (n = 11). After 24 hours, mesenteric lymph nodes, liver, spleen, and systemic blood samples were quantitatively cultured. The terminal ileum was assessed histopathologically. The incidence of bacterial translocation was less in the anesthesia group (two of 12 rats) and the fixation group (two of 11 rats) than in the trauma group (10 of 14 rats). The number of organs containing viable bacteria was significantly lower in the fixation group than in the trauma group. Histopathologically, villous architecture was preserved mostly in the fixation group; however, marked mucosal damage was detected in the trauma group. Our data suggest early internal fixation of long bone fractures in polytraumatized experimental animals with head injury results in preservation of the intestinal mucosal barrier and decreased bacterial translocation from the gut.

Glutamine: do the data support the cause for glutamine supplementation in humans?

This review examines the preclinical rationale for using glutamine supplements and reviews the prospective randomized trials using glutamine to improve outcomes in patients. A special role for glutamine in gut physiology and in management of a variety of serious illnesses has been suggested, because it is the most abundant extracellular amino acid, and is used at high rates by the gut, liver, central nervous system, and immune cells. A state of relative Gln deficiency has been postulated in humans based on the decrease in plasma Gln in acute critical illness, but the decrease in plasma Gln is not specific for that amino acid, predicts only poorer outcome, and has not been validated to identify a deficiency state. Current evidence does not necessarily predict a special need or role for Gln in critical illness. Clinical efficacy of supplemental Gln has been difficult to demonstrate, possibly related to the lack of a Gln deficiency state, the wide range of end points used that reflect the lack of certainty of the predicted effect of supplementation, the heterogeneous patient populations studied, the lack of stable clinical course during the study, the lack of adequate power, and the relatively short follow-up period. Prospective randomized clinical trials of Gln supplementation were reviewed in patients with short-bowel syndrome, during cancer chemotherapy and in bone marrow transplantation, and in surgical, burn, and intensive care unit patients. No firm recommendation can be made at this time. Future studies should seek to develop a more standard and stable design for intervention in sufficiently powered studies.

Bacterial translocation studied in 927 patients over 13 years

BACKGROUND

Bacterial translocation (BT) describes the passage of bacteria from the gastrointestinal tract to normally sterile tissues such as the mesenteric lymph nodes (MLNs) and other internal organs. The clinical and pathophysiological significance of BT remains controversial. This report describes results obtained over a 13-year period of study.

METHODS

MLNs were obtained from 927 patients undergoing laparotomy. Nasogastric aspirates were obtained from 458 (49.4 per cent) of 927 patients for culture; pH was measured in 172 (37.6 per cent) of 458. Preoperative clinical variables were evaluated and factors that influenced BT were included in a multivariate logistic regression analysis.

RESULTS

BT was identified in 130 (14.0 per cent) of 927 patients. Postoperative sepsis was more common in patients with BT (42.3 versus 19.9 per cent; P < 0.001). Independent preoperative variables associated with BT were emergency surgery (P = 0.001) and total parenteral nutrition (TPN) (P = 0.015). Gastric colonization was confirmed in 248 (54.1 per cent) of 458 patients, and was associated with both BT (P = 0.015) and postoperative sepsis (P = 0.029). A gastric pH of less than 4 was associated with a significant reduction in gastric colonization (53 versus 80 per cent; P < 0.001) and postoperative sepsis (46 versus 70.3 per cent; P = 0.018) but not BT.

CONCLUSION

BT is associated with postoperative sepsis. Emergency surgery and TPN are independently associated with an increased prevalence of BT.

Obstructive jaundice increases sensitivity to lipopolysaccharide via TLR4 upregulation: possible involvement in gut-derived hepatocyte growth factor-protection of hepatocytes

BACKGROUND

Patients with obstructive jaundice are prone to sepsis after biliary tract surgery. The present study was designed to determine the effect of biliary obstruction on cytokine responses to lipopolysaccharide (LPS).

METHODS

Wister rats were allocated into two groups; the BDL group underwent bile duct ligation, followed 2 weeks later by administration of LPS into the duodenum. The control group underwent sham operation, and similarly received enteral LPS. Specimens were collected serially, and applied for the assays.

RESULTS

Serum aspartate aminotransferase and alanine aminotransferase levels were significantly increased in BDL rats. High tumor necrosis factor alpha (TNF-alpha) and interleukin (IL)-6 levels in peripheral blood were observed 2 h after LPS administration in BDL rats. In contrast, no increases in both cytokines were noted in peripheral and portal blood in control rats. Baseline HGF levels in portal and peripheral blood in BDL rats were significantly higher than in control rats. LPS significantly increased hepatocyte growth factor (HGF) levels in portal blood and decreased in peripheral blood in BDL rats, but not in control rats. Immunohistochemical analysis revealed that BDL increased expressions of Toll-like receptor (TLR)4, CD14 and CD68 both in the small intestine and liver. Both TLR4 and CD14 mRNAs were upregulated in the small intestine and liver after LPS administration in BDL rats.

CONCLUSION

Obstructive jaundice and LPS stimulation induced TLR4 upregulation both in the liver and small intestine, which led to increased TNF-alpha and IL-6 production in liver and HGF production in the small intestine. The upregulation of TLR4 may lead to pathological and host defense reactions in obstructive jaundice complicated with Gram-negative bacterial infection.

Nutritional Support for Neonatal Foals

In recent years, equine neonatal medicine has made significant advances. The importance of nutritional support for the sick neonatal foal has been recognized, and methods of providing that sup-port have been developed. Today, the clinician has many options when designing a nutritional plan for the neonatal foal. When the foal's gut permits, enteral diets are an inexpensive source of nutrients. Under conditions where the gut requires rest, methods for delivering nutrients by the parenteral route have also been developed. In this article, the nutrition of the normal and sick foal is described. Guidelines for designing a nutritional plan are also reviewed.

The importance of the gastrointestinal system in the pathogenesis of heart failure

Chronic heart failure (CHF) is a multi-organ disease with increasing evidence for the involvement of the gastrointestinal (GI) system in this syndrome. In recent research, the gut has received very little attention from cardiologists as its role in the pathogenesis of cardiovascular disease is poorly understood. Intestinal ischaemia may play an important role in bacterial translocation by increasing bowel permeability. Decreased cardiac function can reduce bowel perfusion and so clearly impairs the function of the intestinal barrier. There is an increasing evidence to suggest that a 'leaky' bowel wall may lead to translocation of bacteria and/or endotoxin, which may be an important stimulus for inflammatory cytokine activation in CHF. Impaired functioning of the GI system may also contribute to malnutrition and cachexia in CHF. It is hoped that by improving our understanding of the role of the gut in cardiac disease will lead to the development of novel therapeutic strategies in the future.

Gut Bacterial Translocation and Postoperative Infections: A Prospective Study in Schistosomotic Patients

BACKGROUND

Bacterial translocation (BT) across the intact intestinal mucosal barrier has been postulated as a source of sepsis in susceptible patients, including those with cirrhosis and portal hypertension. This condition has not been studied in hepatosplenic schistosomiasis, wherein portal hypertension and the presence of an immune deficiency state associated with the parasitic disease could predispose to BT into mesenteric lymph nodes (MLN). A study was conducted to determine the prevalence of aerobic bacteria in MLN (bacterial translocation) of patients with hepatosplenic schistosomiasis, and establish a possible association with postoperative infections.

METHODS

In a series of 51 patients submitted to surgical treatment of schistosomotic portal hypertension with splenectomy and gastric devascularization, MLN were obtained from each patient at the beginning (MLN1) and at the end (MLN2) of the surgical procedure, and sent for bacteriological analysis. Prospective patient evaluation during the postoperative period correlated positive MLN cultures with infectious complications.

RESULTS

The prevalence of aerobic bacteria was 17.6% at MLN1 and 27.5% at MLN2, however, this difference was non-significant (p = 0.24). Bacterial translocation to all MLN was 22.5%. Escherichia coli was the most frequent organism (26.1%, 6/23). The overall incidence of postoperative infections was 19.6% (10/51), with a significant association with the presence of positive cultures of MLN (p = 0.043).

CONCLUSIONS

The findings of this study suggest that the presence of aerobic bacteria on MLN as a consequence of BT may play a role in the development of postoperative infectious complications, particularly in schistosomotic patients.

Intestinal permeability and systemic infections in critically ill patients: effect of glutamine

OBJECTIVE

This article provides a critical review of the evidence indicating that an increase in intestinal permeability is associated with the installation of bacteremia, sepsis, and the multiple organ failure syndrome and that glutamine in pharmacologic doses reduces the acute increase of intestinal permeability and the infection frequency in critically ill patients.

DATA SOURCE

All studies published until December 2004 about intestinal permeability, bacterial translocation, and glutamine were located by search of PubMed and Web of Science. The reference lists of review articles and primary publications were also examined to identify references not detected in the computer search.

STUDY SELECTION

Clinical and experimental studies investigating the correlation between intestinal permeability, bacterial translocation, and frequency of infections, associated or not with the effect of glutamine administration.

DATA EXTRACTION

Information regarding patient population, experimental design, glutamine doses and routes of administration, nutritional therapy prescribed, methods used to assess intestinal permeability, metabolic variables, and the frequency of infections were obtained from the primary literature.

DATA SYNTHESIS

Intestinal permeability is increased in critically ill patients. The results have not always been consistent, but the studies whose results support the association between intestinal permeability and systemic infections have had better design and more appropriate controls. The administration of glutamine by the intravenous or oral route and at the doses recommended before or immediately after surgery, burns, or the administration of parenteral nutrition has a protective effect that prevents or reduces the intensity of the increase in intestinal permeability. Glutamine reduces the frequency of systemic infections and may also reduce the translocation of intestinal bacteria and toxins, but this has not been demonstrated.

CONCLUSIONS

Glutamine administration improves the prognosis of critically ill patients presumably by maintaining the physiologic intestinal barrier and by reducing the frequency of infections.

Adhesion of the probiotic bacterium Lactobacillus plantarum 299v onto the gut mucosa in critically ill patients: a randomised open trial

INTRODUCTION

To achieve any possible positive effect on the intestinal mucosa cells it is important that probiotics adhere tightly onto the intestinal mucosa. It has been shown in healthy volunteers that Lactobacillus plantarum 299v (Lp 299v) (DSM 9843), a probiotic bacterium, given orally in a fermented oatmeal formula adheres onto the intestinal mucosa, but whether this also occurs in critically ill patients is unknown.

METHODS

After randomisation, nine enterally fed, critically ill patients treated with broad-spectrum antibiotics received an oatmeal formula fermented with Lp 299v throughout their stay in the intensive care unit; eight patients served as controls. Biopsies of the rectal mucosa were made at admission and then twice a week, and the biopsies were analysed blindly.

RESULTS

Four patients in the control group were colonised with Lp 299v at admission but thereafter all their biopsies were negative (Lp 299v is an ingredient in a common functional food, ProViva, in Sweden). Of the treated patients none was colonised at admission but three patients had Lp 299v adhered on the mucosa from the second or third biopsy and in the following samples.

CONCLUSION

This study shows that Lp 299v could survive the passage from the stomach to the rectum and was able adhere onto the rectal mucosa also in critically ill, antibiotic-treated patients.

Bacterial translocation in the normal human appendix parallels the development of the local immune system

Experimental modes and pathological conditions may result in bacterial translocation (BT), that is, the passage of indigenous bacteria colonizing the intestine through the intestinal mucosa to mesenteric lymph nodes. Yet no data are available on BT in the normal human gut. We determined the occurrence of BT and its extent in histologically normal, incidentally removed human vermiform appendices (VA) from individuals of different ages and correlated the findings with the development with age of associated lymphatic tissue. BT appears to pertain to normal antigen-sampling processes of the GALT in the VA. It also parallels the development of the GALT and its maintenance during adulthood. In the first two weeks after birth, when bacterial colonization of the gut evolves and when the VA lacks the protection of secretory IgA, BT was not detected. Thereafter, BT occurs along with development of the local GALT, which is fully built up after the first year. A physiological uptake of, or invasion by, bacteria may be instrumental (1) for tolerance induction against the indigenous flora and (2) for the stimulation and normal development of the GALT.

Bacterial translocation (BT) in cirrhosis

Gut flora and bacterial translocation (BT) play an important role in the pathogenesis of the complications of cirrhosis. Research on the pathogenesis of BT and its clinical significance transcends established boundaries between microbiology, cell biology, intestinal pathophysiology, and immunology. This review delineates multiple mechanisms involved in the process of BT, with an emphasis on alterations in intestinal flora and mucosal barrier function, particularly immunological defense mechanisms. Current knowledge on the innate and adaptive immune response that allows a "friendly" communication between bacteria and host is summarized, and alterations occurring in cirrhosis that may facilitate BT are discussed. In addition, definition of a "pathological" BT is proposed together with an analysis of the anatomical site and route of BT. Finally, therapeutic approaches for the prevention of BT in experimental and human cirrhosis are reviewed. Future research in the field of BT in cirrhosis will allow the development of new therapeutic targets in the prevention of infections and other complications of cirrhosis.

Bacterial Translocation: Not a Clinically Relevant Phenomenon in Colorectal Cancer

The aim of this study was to identify the risk factors for bacterial translocation and to determine the clinical significance of bacterial translocation in patients with colorectal cancer. Mesenteric lymph node sampling was performed to identify the presence of bacterial translocation in 75 patients with colorectal cancer undergoing laparotomy. Bacterial translocation was identified in 29 patients (39%), with the most common organism being Escherichia coli (31%). Three factors for bacterial translocation were identified, including a preoperative low peripheral lymphocyte count, metastasis to lymph nodes, and invasion depth (= T3). Stepwise regression analysis, however, selected only = T3 [odds ratio (OR) 4.0, 95% confidence interval (CI) 1.2-13.5]. Altogether, 35% of patients with bacterial translocation developed septic complications, compared with 20% in patients without bacterial translocation. In the multivariate analysis, bacterial translocation was not an independent risk factor for infection, with an OR of 1.8 (95% CI 0.56-5.96). Systemic inflammatory response syndrome developed on the first day in 62% of patients with bacterial translocation, compared with 50% of patients without bacterial translocation. Adjusting for the other factors, bacterial translocation was not a significant risk factor in the occurrence of systemic inflammatory response syndrome after surgery (OR 1.1, 95% CI 0.37-3.29). We concluded that in patients with colorectal cancers bacterial translocation does occur and is increased in patients with deep invasion. However, it appears to be of no clinical significance.

Modulation of Cytokine Release by Differentiated CACO-2 Cells in a Compartmentalized Coculture Model with Mononuclear Leucocytes and Nonpathogenic Bacteria

To further investigate the interaction between human mononuclear leucocytes [peripheral blood mononuclear cells (PBMC)] and enterocytes, the effect of a confluent layer of differentiated CACO-2 cells on cytokine kinetics during challenge with bacteria in a compartmentalized coculture model was investigated. Nonpathogenic Escherichia coli were added either to the apical or the basolateral compartment of this transwell cell culture system, the latter of which contained human leucocytes. The synthesis of tumour necrosis factor (TNF-alpha) and interleukin (IL)-12 was significantly suppressed by CACO-2 cells when leucocytes were stimulated directly with bacteria. This suppression was not paralleled by changes in the production of IL-10, IL-6 and transforming growth factor (TGF)-beta. When the bacteria were applied apically to the CACO-2 cell layer, the production of TNF-alpha, IL-12, IL-1beta, IL-8, IL-6, IL-10, TGF-beta and interferon-gamma was pronouncedly lower as compared to the bacterial stimulation of leucocytes beneath the CACO-2 cells. In the latter experiments, IL-6, IL-8 and TNF-alpha were the cytokines being mostly induced by apical addition of E. coli. Quantitative mRNA expression analysis revealed that IL-8 gene expression was equally induced in both CACO-2 and PBMC after apical stimulation with bacteria. Of note, bacteria-stimulated CACO-2 cells produced little or no cytokines in the absence of leucocytes, supporting the concept of leucocyte-epithelial cell cross-talk in modulating cytokine responses in the gut mucosa.

Failure of the gut barrier system enhances liver injury in rats: protection of hepatocytes by gut-derived hepatocyte growth factor

OBJECTIVE

Clinical and experimental studies suggest that impairment of the mucosal barrier system increases gut-derived endotoxin in the portal blood, which causes liver injury. The aim of this study was to elucidate the mechanism of liver injury caused by gut defence failure.

DESIGN

Wistar rats were administered either enteral lipopolysaccharide (LPS) or LPS via the portal vein.

METHODS

Blood samples were collected via the inferior vena cava at necropsy. Serum aspartate transaminase (AST) and alanine transaminase (ALT) were analysed by standard enzymatic procedures and cytokines [tumour necrosis factor-alpha, interleukin (IL)-1beta, interferon-gamma, IL-6 and hepatocyte growth factor (HGF)] were measured by enzyme-linked immunosorbent assay. Livers were removed and snap-frozen in liquid nitrogen. CD14, CD68, Toll-like receptor (TLR) 2, TLR4 and Fas ligand (FasL) were analysed immunohistochemically. Expression of TLR2, TLR4 and CD14 mRNA was determined by reverse transcriptase-polymerase chain reaction.

RESULTS

In enterally-treated rats, AST and ALT were not increased and cytokine levels were under the limits of detection in the absence of a rise in HGF. Enteral administration of LPS increased HGF dose-dependently. Injection of LPS in the portal vein resulted in significant increases in AST, ALT, tumour necrosis factor-alpha, IL-1beta, interferon-gamma and IL-6 levels, but no change in HGF levels. Immunohistochemical analysis revealed that intraportal LPS administration increased CD14, TLR4, CD68 and FasL. Reverse transcriptase-polymerase chain reaction analysis demonstrated that TLR4 mRNA expression was upregulated 0.5 h after intraportal LPS administration.

CONCLUSION

s Our data suggest that Kupffer cell activation mediated by intraportal LPS via TLR4 is involved in liver injury, possibly through both tumour necrosis factor-alpha/IL-1beta and FasL, and that lack of HGF activity in the impaired gut could not counteract liver injury.

Albumin protects against gut-induced lung injury in vitro and in vivo

OBJECTIVE

Since albumin has the ability to detoxify, we assessed whether low-dose albumin could protect against trauma/hemorrhagic shock (T/HS)-induced endothelial cell, lung, gut, and red blood cell (RBC) injury in vivo and endothelial cell injury in vitro.

SUMMARY BACKGROUND DATA

T/HS cause ischemic insult to the gut, resulting in the release of biologically active factors into the mesenteric lymph, which then cause injury to multiple distant organs.

METHODS

In vitro experiments tested the ability of albumin to reduce the cytotoxicity of mesenteric lymph from male rats subjected to T/HS (laparotomy + MAP 30 mm Hg for 90 minutes) for human umbilical vein endothelial cell (HUVEC). In subsequent in vivo experiments, the ability of albumin given as part of the resuscitation regimen to protect against T/HS-induced injury was tested by comparing the magnitude of injury in T/HS rats receiving human albumin (shed blood + 0.12, 0.24, or 0.36 g/kg) or lactated Ringer's solution (shed blood + 2 x volume of shed blood as LR) with that observed in rats subjected to trauma/sham shock. Rats were killed after a 3-hour recovery period and had lung permeability evaluated by bronchoalveolar lavage and myeloperoxidase assays, intestinal microvillous injury by histology, and RBC deformability using ektacytometry.

RESULTS

Both bovine and human albumin prevented T/HS lymph-induced HUVEC cytotoxicity in vitro, even when added 30 minutes after the lymph (viability 15 +/- 4% to 88 +/- 3%, P < 0.01). In vivo RBC deformability was better preserved by blood plus albumin than blood plus lactated Ringer's solution (P < 0.01). Likewise, albumin administration reduced T/HS-induced lung permeability and neutrophil sequestration in a dose-dependent fashion, with 0.36 g/kg of albumin effecting total lung protection (P < 0.01). In contrast, albumin treatment did not prevent T/HS-induced gut injury.

CONCLUSIONS

Low-dose albumin protects against gut lymph-induced lung, HUVEC, and RBC injury by neutralizing T/HS lymph toxicity.

A review of the trends in the use of enteral and parenteral nutrition support

This is a review article that discusses the trends in the use of enteral and parenteral nutrition support. Although enteral nutrition has existed longer than parenteral nutrition, only recent data would suggest a clinical benefit of enteral nutrition compared with parenteral nutrition. In this article, indications for parenteral nutrition are listed. Also, data comparing bacterial translocation and complications associated with both forms of nutritional support are discussed. Clinical outcome in specific gastrointestinal diseases is also discussed.

Probiotics partly reverse increased bacterial translocation after simultaneous liver resection and colonic anastomosis in rats

BACKGROUND

Bacterial translocation is one important cause of nosocomial infections following major abdominal surgery. Oral administration of probiotics has been proposed to diminish bacterial translocation.

MATERIAL AND METHODS

In total 68 rats were divided into seven groups: five of the groups received standard rat chow and were subjected to either sham-operation, 70% liver resection, colonic anastomosis, or a combination of 30 or 70% liver resection with synchronous colonic anastomosis, respectively. In two additional groups with synchronous operation, a combination of four different lactic acid bacteria and four fibers was administered two times daily pre- and postoperatively. Bacterial concentrations in cecum, mesenteric lymph nodes, liver, and spleen were analyzed and blood cultures were taken 48 h after operation. Furthermore, the following parameters were assessed: histological changes in the intestine, intestinal paracellular permeability (Ussing chamber), bursting pressure of the colonic anastomosis, and mitosis rate of the remnant liver.

RESULTS

Bacterial translocation was observed in all rats, except in the sham group. Following liver resection, the highest bacterial concentrations were seen in liver and spleen, following colon anastomosis in the mesenteric lymph nodes. Bacterial translocation was increased in the animals with combined operation, in parallel to the extent of liver resection. In rats with colon anastomosis, bacterial concentration in the cecum was also higher than in the sham group. Application of probiotics significantly decreased bacterial concentration in the lymph nodes. In addition, animals with a high cecal concentration of lactobacilli had less translocation than the others. No histological changes were observed in the intestine. Paracellular permeability for ions, but not for the larger molecule lactulose, was increased in the colon in all groups with colon anastomosis. The bursting pressure of the colon anastomosis was not significantly different between the groups. Seventy percent liver resection led to a high rate of hepatocyte mitosis, whereas combination with colon anastomosis impaired the regeneration process.

CONCLUSION

Synchronous liver resection and colon anastomosis led to increased bacterial translocation compared to the single operations in the rat model. It is possible to diminish this process by oral administration of probiotics. Bacterial overgrowth in the cecum and impaired hepatic regeneration, but not histological changes or alterations of paracellular permeability, are potential pathogenic mechanisms for translocation in this setting.

Assessment of the role of antibiotics and enterococcal virulence factors in a mouse model of extraintestinal translocation

OBJECTIVE

To study the relative contribution of antibiotics and bacterial virulence factors in the process of translocation of Enterococcus faecalis from the gut to extraintestinal organs.

DESIGN

Prospective controlled animal study.

SETTING

Animal experimental laboratory at a university medical center.

SUBJECTS

Fifty-two female Balb/c mice.

INTERVENTIONS

We developed a mouse model to study the translocation of Enterococcus faecalis from the intestinal tract. Balb/c mice received sterile drinking water or antibiotic combinations to deplete their indigenous intestinal microflora. The animals subsequently were fed genetically engineered enterococci expressing different combinations of the putative enterococcal virulence factors aggregation substance and binding substance. Animals were killed, and their livers, spleens, and mesenteric lymph nodes were aseptically removed and cultured along with fecal samples for enumeration of bacteria.

MEASUREMENTS AND MAIN RESULTS

All animals were colonized with the test strains at 2-6 x 109 colony forming units/g of feces; in the antibiotic-treated animals, feces were free from anaerobes and Enterobacteriaceae. In animals fed the identical bacterial mutant, the colony counts in mesenteric lymph nodes were significantly lower in mice not treated with antibiotics than in those treated with antibiotics (p =.016). Multigroup analysis of variance revealed no significant differences of the translocation frequencies for the different mutant strains; however, the differences were statistically significant for all groups receiving antibiotics vs. the group not receiving antibiotics (p <.05-.01). There was a trend (although not statistically significant) for a higher proportion of positive cultures from either spleen or liver in mice that had enterococci recovered from their mesenteric lymph nodes (28%) relative to those that did not have enterococci isolated from the lymph nodes (12%; rate ratio 2.39, p =.30 by logistic regression analysis).

CONCLUSIONS

Oral antibiotics can select for extraintestinal translocation of Enterococcus faecalis, and neither aggregation substance nor binding substance seems to be required for this process. The experiments encourage further exploration of host and microbial factors contributing to translocation and may provide a better understanding of the pathogenesis of enterococcal infections in patients in intensive care units.

Hepatobiliary, renal and bone complications of intestinal failure

Abnormal liver function tests in patients with intestinal failure (IF) may be due to the underlying disease, IF or the treatments given (including parenteral nutrition (PN)). PN-related liver disease in children usually relates to intrahepatic cholestasis and in adults to steatosis. Steatosis may be consequent upon an excess of carbohydrate, lipid or protein, or upon a deficiency of a specific molecule. Pigment-type gallstones are common in adults and children with IF; these develop from biliary sludge that forms during periods of gallbladder stasis. Ileal disease/resection, parenteral nutrition, surgery, rapid weight loss and drugs all increase the risk of developing gallstones. Gallstone formation may be prevented by reducing gallbladder stasis (oral/enteral feeding or prokinetic agents), altering bile composition, or by means of a prophylactic cholecystectomy. Calcium oxalate renal stones are common in patients with a short bowel and retained functioning colon and are consequent upon increased absorption of dietary oxalate; they are prevented by a low-oxalate diet. An osteopathy may occur with long-term parenteral nutrition.

Providencia alcalifaciens strains translocate from the gastrointestinal tract and are resistant to lytic activity of serum complement

The ability of Providencia alcalifaciens strains, isolated from patients with diarrhoeal disease, to translocate from the gastrointestinal tract and their resistance to serum complement lytic activity were investigated and compared with previously characterized differential invasive capabilities in HeLa cells. Translocation ability to several extraintestinal sites and resistance to lysis by human serum complement were observed in both highly invasive and non-invasive strains. These characteristics have not been previously described in P. alcalifaciens and their potential role in causing disseminated infections should therefore be considered.

Gastrointestinal disorders of the critically ill. Bacterial translocation in the gut

The human gastrointestinal tract is colonized by a dense population of microorganisms, referred to as the bacterial flora. Although the gut provides a functional barrier between these organisms and the host, bacterial translocation is a common event in the healthy person. However, in critically ill patients, with various underlying diseases, this bacterial translocation may lead to infections and consequently to a further reduction in general health status. The mechanism of bacterial translocation is widely, and somehow controversially investigated in vitro and in animal models. In human studies, several diseases have been associated with bacterial translocation. However, methodological shortcomings, insufficient populations and conflicting results leave many open questions. This is also reflected in the various published therapeutic strategies. To overcome this problem more investigations in humans are needed, especially in techniques for detecting bacterial translocation.

Bacterial translocation after cirrhotic liver resection: a clinical investigation of 181 patients

BACKGROUND

Cirrhotic patients are usually associated with a high susceptibility to infection. Although bacterial translocation from gut mucosa to mesenteric lymph node (MLN) and systemic circulation is a well-known phenomenon after hepatectomy, its role in cirrhotic patients remains unclear.

MATERIALS AND METHODS

MLN was harvested for bacterial culture before and after liver resection in 181 cirrhotic patients. The characteristics and postoperative courses of patients with positive and negative bacterial culture for MLN after hepatectomy were compared. Postoperative systemic antibiotics were administered if infectious complications occurred.

RESULTS

No bacteria were cultured in MLN before hepatectomy. Bacterial translocation (BT) to MLN after hepatectomy occurred in 36 patients (BT group). After multivariate analysis, intraoperative blood transfusion was the only independent factor that influenced bacterial translocation rates after cirrhotic liver resection. BT group patients also had higher infectious and overall complication rates, with a longer postoperative hospital stay. Among the cultured bacteriae from infected sites in BT group patients with infectious complications, only 2 patients (12.5%) had totally different bacterial species to those cultured from MLNs.

CONCLUSIONS

Bacterial translocation more often occurred after liver resection in cirrhotic patients who received intraoperative blood transfusion. Such patients had higher postoperative infectious and overall complication rates. Thus, avoidance of intraoperative blood transfusion is mandatory for cirrhotic liver resection.

Intestinal mucosal oxidative damage and bacterial translocation in cirrhotic rats

BACKGROUND

Bacterial translocation plays an important role in the pathogenesis of spontaneous bacterial peritonitis mainly due to intestinal bacterial overgrowth. Alterations in the functional integrity of the intestinal barrier caused by an increased production of free radical metabolites as a consequence of portal hypertension could also facilitate bacterial translocation in cirrhotic rats.

OBJECTIVE

The aim of the study was to determine intestinal mucosal lipid peroxidation and neutrophil infiltration and their relationship with portal hypertension and bacterial translocation in cirrhotic rats.

DESIGN

Eighteen male Sprague-Dawley rats with cirrhosis induced by carbon tetrachloride, administered by gavage, and eight control rats were included in the study.

METHODS

Samples of jejunum, ileum and caecum were obtained by laparotomy for the determination of malondialdehyde and myeloperoxidase as indexes of lipid peroxidation and neutrophil infiltration, respectively. Samples of ascitic and pleural fluids, mesenteric lymph nodes and ileal stools were obtained for the culture of microoganisms.

RESULTS

The concentration of malondialdehyde was significantly higher in ileal and caecal, but not in jejunal mucosa, in cirrhotic rats, mainly in those with ascites (P< 0.01), as compared to control rats (P< 0.01), and in cirrhotic rats with bacterial translocation compared to those without bacterial translocation (P< 0.01). No differences between groups were observed in the concentrations of myeloperoxidase in jejunum, ileum or caecum. A direct correlation between ileal malondialdehyde and portal pressure was observed (P< 0.01).

CONCLUSIONS

Cirrhotic rats, particularly those with ascites and bacterial translocation, show increased malondialdehyde levels in ileal and caecal mucosa. These results suggest that mucosal oxidative damage in ileum and caecum could favour bacterial translocation in cirrhotic rats.

Bacterial translocation: clinical implications and prevention

The occurrence of BT has been well documented in experimental animal models of hemorrhagic shock, trauma, severe burns, cirrhosis, pancreatitis, and bacterial overgrowth. Translocation of viable bacteria and endotoxins into mesenteric lymph nodes and other gut-associated lymphatic tissue is thought to activate a complex interplay of mediators that initiates the SIRS. Multiple humoral and cellular systems cause synthesis, expression, and release of inflammatory mediators, such as toxic oxygen radicals, proteolytic enzymes, adherence molecules, and various cytokines. A massive sustained proinflammatory response can ultimately result in irreversible multiple organ dysfunction. Because BT is associated with splanchnic hypoperfusion, the cornerstone of therapy involves rapid resuscitation and restoration of tissue perfusion. If a septic focus can be identified, it should be removed. Gut protectants, promotility agents, antioxidants, and immune-enhancing diets have shown promise in improving length of survival in these critically ill patients.

Microscopy of bacterial translocation during small bowel obstruction and ischemia in vivo--a new animal model

BACKGROUND

Existing animal models provide only indirect information about the pathogenesis of infections caused by indigenous gastrointestinal microflora and the kinetics of bacterial translocation. The aim of this study was to develop a novel animal model to assess bacterial translocation and intestinal barrier function in vivo.

METHODS

In anaesthetized male Wistar rats, 0.5 ml of a suspension of green fluorescent protein-transfected E. coli was administered by intraluminal injection in a model of small bowel obstruction. Animals were randomly subjected to non-ischemic or ischemic bowel obstruction. Ischemia was induced by selective clamping of the terminal mesenteric vessels feeding the obstructed bowel loop. Time intervals necessary for translocation of E. coli into the submucosal stroma and the muscularis propria was assessed using intravital microscopy.

RESULTS

Bacterial translocation into the submucosa and muscularis propria took a mean of 36 +/- 8 min and 80 +/- 10 min, respectively, in small bowel obstruction. Intestinal ischemia significantly accelerated bacterial translocation into the submucosa (11 +/- 5 min, p < 0.0001) and muscularis (66 +/- 7 min; p = 0.004). Green fluorescent protein-transfected E. coli were visible in frozen sections of small bowel, mesentery, liver and spleen taken two hours after E. coli administration.

CONCLUSIONS

Intravital microscopy of fluorescent bacteria is a novel approach to study bacterial translocation in vivo. We have applied this technique to define minimal bacterial transit time as a functional parameter of intestinal barrier function.

The effects of pentoxifylline on bacterial translocation after intestinal obstruction

Bacterial translocation (BT) occurs mainly in preseptic conditions such as intestinal obstruction, trauma, and burn, and the underlying mechanisms are still unclear. Pentoxifylline (PTX) is a derivative of methyl xanthine and has several beneficial effects in sepsis. We investigated the effects of PTX on a rat BT model. Simple intestinal obstruction (IO) was choosen to create high BT rates. Rats were divided in to five groups of 10 rats. Either 50 mg/kg PTX or placebo (3 mg/100 g saline) was administered subcutaneously following IO, either by single injection or twice with a 12-h interval. All rats were sacrificed 12 or 24 h after the procedure, and mesenteric lymph nodes (MLN), liver, and blood samples were obtained under aseptic conditions for bacterial cultures. The samples were obtained 12 h following IO in the first two groups, and the same samples were obtained 24 h after IO in last three groups. Groups IV and V were the PTX treatment groups. PTX was re-injected 12 h after IO only in group IV. As a result, BT rates in MLNs and liver were found to be significantly low, blood specimens remained sterile in PTX-pretreated and -treated rats, and BT rates were high in control groups and group V (once treatment late specimen group). We conclude that simple intestinal obstruction causes BT, and PTX reduces BT in rats with IO during the first 12-h period if PTX is given once immediately following IO. PTX reduces BT during the first 24-h after IO provided that is injected twice with a 12-h interval. More experimental studies are need to explain the exact mechanism of this beneficial effect.

Early enteral supply of fiber and Lactobacilli versus conventional nutrition: a controlled trial in patients with major abdominal surgery

OBJECTIVE

Early enteral nutrition with fiber-containing solutions plus Lactobacillus may reduce bacterial translocation and minimize the incidence of infections after surgery.

METHODS

In a prospective, randomized trial in three groups (n = 30/group) of patients after major abdominal surgery, we compared our previous regimen with parenteral nutrition or fiber-free enteral nutrition (group A) with enteral fiber-containing nutrition with living Lactobacillus (group B) and heat-killed Lactobacillus (group C). The main endpoint was the development of bacterial infection. Other analyzed parameters were the durations of antibiotic therapy and hospital stay, non-infectious complications, side effects of the nutrition, and onset of bowel movement. Routine parameters, nutritional parameters, and cellular immune status in the blood were measured preoperatively and on 1, 5, and 10 d postoperatively.

RESULTS

The incidence of infections was significantly lower (P = 0.01) in groups B and C with enteral nutrition containing fibers (10% each) than in group A (30%). Patients in group B received antibiotics for a significantly shorter time (P = 0.04) than did the patients in groups A and C. The length of hospital stay and the incidence of non-infectious complications did not differ significantly. Fibers and lactobacilli were well tolerated. There were no general benefits of living Lactobacillus as opposed to heat-killed Lactobacillus in the entire study population, but benefits were observed in the patients with gastric and pancreas resections, although no statistical analysis was done due to their small numbers.

CONCLUSIONS

Early enteral nutrition with fiber-containing solutions reduced the rate of postoperative infections in comparison with parenteral nutrition and fiber-free enteral formula. Addition of living Lactobacillus seemed to increase the benefits in patients with gastric and pancreatic resections.

Intestinal permeation and gastrointestinal disease

The gastrointestinal tract constitutes one of the largest sites of exposure to the outside environment. The function of the gastrointestinal tract in monitoring and sealing the host interior from intruders is called the gut barrier. A variety of specific and nonspecific mechanisms are in operation to establish the host barrier; these include luminal mechanisms and digestive enzymes, the epithelial cells together with tight junctions in between them, and the gut immune system. Disruptions in the gut barrier follow injury from various causes including nonsteroidal anti-inflammatory drugs and oxidant stress, and involve mechanisms such as adenosine triphosphate depletion and damage to epithelial cell cytoskeletons that regulate tight junctions. Ample evidence links gut barrier dysfunction to multiorgan system failure in sepsis and immune dysregulation. Additionally, contribution of gut barrier dysfunction to gastrointestinal disease is an evolving concept and is the focus of this review. An overview of the evidence for the role of gut barrier dysfunction in disorders such as Crohn's disease, celiac disease, food allergy, acute pancreatitis, non-alcoholic fatty liver disease, and alcoholic liver disease is provided, together with critical insight into the implications of this evidence as a primary disease mechanism.

Alterations in serum anti-alpha-galactosyl antibodies in patients with Crohn's disease and ulcerative colitis

Anti-galactosyl alpha1-3-galactosyl (anti-Gal) is a natural serum antibody abundantly produced in humans in response to immune stimulation by enteric bacteria. Marked elevation of its titer has been detected in parasitic diseases and in some autoimmune disorders. Because persistent intestinal infection and defective mucosal barrier have been suggested as potential etiologic agents of inflammatory bowel disease, the aim of this study was to analyze the sera levels of anti-Gal antibodies in patients with Crohn's disease and ulcerative colitis. An ELISA assay was performed to analyze circulating antibody using the disaccharide Gal (alpha 1-3)Gal coupled to human serum albumin as antigen and alkaline phosphatase-conjugated rabbit anti-human immunoglobulin G, A, M as antibody. Immunoglobulin classes were assayed using class-specific antibodies. The optical densities of sera from Crohn's disease (1.83 +/- 0.63) and ulcerative colitis (1.45 +/- 0.7) were significantly higher (P < 0.0001 and P < 0.0005, respectively) than those of the control group (0.97 +/- 0.39). In Crohn's disease the increase was distributed among the three immunoglobulin classes; in ulcerative colitis a significant increase was observed only for immunoglobulin A. The increased levels of circulating antibodies against Gal (alpha 1-3)Gal in the presence of intestinal bacterial strains expressing antigenic epitopes and breakdown of mucosal barrier could contribute to the dysregulated immune response observed in inflammatory bowel disease.

Bacterial translocation: effects of artificial feeding

The most striking observation when reviewing recent literature in the field of bacterial translocation in the intestine is the small number of publications involving human subjects. Although there are some excellent reviews in this field published during the last 2 years, all experimental contributions come from animal experiments. It is therefore crucial to evaluate how valid the animal models are for human pathophysiology. Studies focusing on translocation as a major pathogenic mechanism are urgently needed to help clinicians to make correct decisions concerning protection of the gut and decide upon nutrition in the intensive care unit.