Pathogenesis Of Diarrhea Research Articles

Verocytotoxins (Shiga-like toxins) produced by Escherichia coli: a minireview of their classification, clinical presentations and management of a heterogeneous family of cytotoxins

Bacterial virulence usually requires the interaction of multiple factors in order to cause disease. The enterotoxins produced by certain strains of bacteria are proteins which vary in their mode of action, but do fall into two general groups; the cytotoxic and the cytotonic enterotoxins. While cytotoxic enterotoxins typically kill eucaryotic cells (eg. by inhibiting protein synthesis), cytotonic enterotoxins derange cell metabolism in specific ways (eg. by elevating cyclic nucleotide levels). Some strains of Escherichia coli produce protein toxins that are biologically, structurally and antigenically related to a cytotoxin (Shiga toxin) (ShT) produced by Shigella dysenteriae type 1. Although this group of related, but not necessarily identical toxins have been referred to as Vero cell toxins or Verocytotoxins (VTs), the term Shiga-like toxins (SLTs) has been widely accepted. ShT and SLTs have been implicated as a cause of diarrhoea as well as haemorrhagic colitis (HC) and haemolytic uremic syndrome (HUS) in humans, whilst SLTs have been implicated as causal agents of oedema disease and HC in weaner pigs and calves, respectively. While S. dysenteriae is an invasive organism, the SLT-producing strains of E. coli have not been reported to be invasive, but cause diarrhoea that may contain blood and mucus. Thus, SLTs can be considered an important “new” type of enterotoxins whose role in the pathogenesis of diarrhoea, HC and HUS is beginning to emerge, not only in certain geographical settings, but worldwide. This mini review focuses on this family of SLTs, because of recent advances which have been made towards their detection, nomenclature, pathogenesis and possible management of their clinical presentations.

Intestinal inflammation reduces expression of DRA, a transporter responsible for congenital chloride diarrhea.

The pathogenesis of diarrhea in intestinal inflammatory states is a multifactorial process involving the effects of inflammatory mediators on epithelial transport function. The effect of colonic inflammation on the gene expression of DRA (downregulated in adenoma), a chloride-sulfate anion transporter that is mutated in patients with congenital chloridorrhea, was examined in vivo as well as in an intestinal epithelial cell line. DRA mRNA expression was diminished five- to sevenfold in the HLA-B27/beta2m transgenic rat compared with control. In situ hybridization showed that DRA, which is normally expressed in the upper crypt and surface epithelium of the colon, was dramatically reduced in the surface epithelium of the HLA-B27/beta2m transgenic rat, the interleukin-10 (IL-10) knockout mouse with spontaneous colitis, and in patients with ulcerative colitis. Immunohistochemistry demonstrated that mRNA expression of DRA reflected that of protein expression in vivo. IL-1beta reduced DRA mRNA expression in vitro by inhibiting gene transcription. The loss of transport function in the surface epithelium of the colon by attenuation of transporter gene expression, perhaps inhibited at the level of gene transcription by proinflammatory cytokines, may play a role in the pathogenesis of diarrhea in colitis.

Role of the large intestine in the pathogenesis of diarrhea in weaned pigs

Abstract Objective To determine whether the large intestine may have a role in counterbalancing the loss of fluid from the small intestine of pigs with diarrhea. Animals 2 groups of pigs (1 from a specific-pathogen-free herd and 1 from a herd with a history of diarrhea). Procedure At weaning and 4, 7, 11, and 14 days after weaning, the percentage of dry matter in the large intestinal contents, total and individual concentrations of volatile fatty acids in large-intestinal contents and blood, and concentration of aldosterone in the blood were measured. Results Large intestinal contents of pigs with diarrhea had a lower percentage of dry matter, lower acetate and butyrate concentrations, and higher propionate concentrations than did those of specific-pathogen-free pigs, and blood of pigs with diarrhea also had lower total volatile fatty acids concentration, higher aldosterone concentration, and lower sodium concentration. Clinical Relevance The large intestine has a role in the pathogenesis of diarrhea in weaned pigs. (Am J Vet Res 1998;59:696-703)

DIARRHEAL DISEASES ASSOCIATED WITH HIV INFECTION

Diarrhea is a major complication of HIV infection and adversely impacts health care costs, quality of life, and even survival of patients. There is a wide variety of potential causes of diarrhea in HIV-infected patients, and the number of pathogens found continues to increase with time. In addition, there is some controversy concerning the role of some organisms in the pathogenesis of diarrhea and the appropriate diagnostic evaluation of affected patients. This article reviews our current understanding of these pathogens and some of the diagnostic and therapeutic approaches for diarrhea associated with HIV infection.

PRODUCTION OF ARACHIDONIC ACID LIPOXYGENASE METABOLITES BY THE INTESTINAL EPITHELIAL CELL LINE HT29 CL. 19A AND THEIR EFFECT ON CHLORIDE SECRETION.

Arachidonic acid (AA) lipoxygenase products may be important in the pathogenesis of diarrhoea associated with intestinal inflammation, because they may stimulate electrogenic chloride secretion in the epithelium. However, the role of the epithelial cells as producers or as targets for lipoxygenase products remains controversial. To clarify this role, we measured the following on the same clone of a chloride-secreting intestinal cell line of human origin (HT29 cl. 19A): 1) the expression of the mRNAs of 5-lipoxygenase, platelet and leukocyte type 12-lipoxygenase, 15-lipoxygenase, LTA4 hydrolase, Five-Lipoxygenase-Activating-Protein (FLAP), prostaglandin H (PGH) synthase-1 and PGH synthase-2 after total RNA extraction, reverse transcription and cDNA amplification by PCR, using specific primers; 2) the formation of AA metabolites by high pressure liquid chromatography (HPLC) and 3) the effect of such metabolites on the stimulation of short-circuit current (Isc). an index of chloride secretion, in filter-grown HT29 cl. 19A cells mounted in Ussing chambers. Results: The mRNAs of 5-lipoxygenase, 15-lipoxygenase, LTA4 hydrolase, PGH synthase-1 and PGH synthase-2 were equally expressed in HT29 cl. 19A cells at different stages of culture, but FLAP, platelet and leukocyte type 12-lipoxygenase mRNAs were not expressed. When dispersed HT29 cl. 19A cells were incubated with [1-14C] arachidonic acid, calcium ionophore A23187, Mg2+ and Ca2+, they produced 5-hydroxyeicosatetraenoic acid (5-HETE), 15-hydroxyeicosatetraenoic acid (15-HETE), and a peak containing leukotriene B4 (LTB4) unresolved from its 6-trans-stereoisomers, and 5(S)-12(S)-di-HETEs. No peptidoleukotriene were detected. Unlabelled AA metabolites, analyzed by HPLC and enzyme immunoassay, were mainly 6-trans-stereoisomers of LTB4 and unidentified di-HETEs, but only a small amount of LTB4 was detected. In addition to prostaglandin E2 (PGE2), which was the most potent compound, several hydroperoxyeicosatetraenoic acids (HPETEs) produced by autoxidation of AA (5-, 9-, 11-, 12- and 15-HPETEs) induced bumetanide-sensitive chloride secretion by HT29 cl. 19A cells (Δ Isc: 3.2 ± 0.4 to 12.1 ± 3.7 μA cm-2). The 9-, 12- and 15-HETEs obtained by triphenylphosphine reduction of the corresponding HPETEs, displayed the same activity as the parent compound, but the 5- and 11-HETEs lose their potencies. LTB4 had no effect on chloride secretion. The present results suggest that the enterocyte may participate in the production of AA metabolites through the lipoxygenase and prostaglandin synthase pathways. In addition, the enterocytes are a target for the lipoxygenase pathway metabolites they and other cells produce.

Human intestinal epithelial cells swell and demonstrate actin rearrangement in response to the metalloprotease toxin of Bacteroides fragilis.

Enterotoxigenic Bacteroides fragilis (ETBF) cells produce a 20-kDa heat-labile metalloprotease toxin which is potentially important in the pathogenesis of diarrhea associated with this infection. Previous studies indicate that subconfluent HT29/C1 cells treated with the B. fragilis toxin (BFT) develop morphologic changes with dissolution of tight clusters and apparent swelling. Such alterations suggest toxin-stimulated reorganization of the cellular cytoskeleton. The purpose of the current study was to evaluate the effect of BFT on actin microfilaments (F-actin) and cell volume. As assessed by fluorescent phallicidin staining which detects F-actin, BFT treatment of HT29/C1 cells resulted in redistribution of F-actin with loss of stress fibers, a floccular staining pattern, and cellular membrane blebbing without quantitative changes in F-actin fluorescence intensity. The F-actin redistribution was time and concentration dependent. In contrast to the cell shrinkage observed in response to the F-actin-depolymerizing agents cytochalasin D and Clostridium difficile toxin A, BFT stimulated an increase in HT29/C1 cell volume of 10 to 25% (compared with control cells) over a 24-h time course. Only 10 to 30 ng of BFT per ml was necessary to stimulate a maximal increase in HT29/C1 cell volume. The effect of BFT on cell volume was persistent and dependent on the proteolytic activity of BFT. In agreement with cell viability assays indicating that BFT did not injure HT29/C1 cells, intoxicated cells exhibited regulatory volume decrease, suggesting that toxin-treated cells remain physiologically dynamic. We conclude that BFT acts on the intestinal epithelial cell cytoskeleton to alter F-actin structure and to stimulate an increase in HT29/C1 cell volume. Although these two activities of BFT appear to be linked, the precise sequence of cellular events following intoxication of HT29/C1 cells with BFT remains unclear. We hypothesize that these F-actin and cell volume changes may lead to an alteration in tight junction function in the polarized intestinal epithelium, contributing to the pathogenesis of diarrhea in ETBF infections.

Tumor necrosis factor-alpha induces Cl- and K+ secretion in human distal colon driven by prostaglandin E2.

Increased levels of tumor necrosis factor-alpha (TNF-alpha) have been found in, for example, inflammatory bowel disease (IBD) and human immunodeficiency virus (HIV) infection. To investigate a possible contribution of TNF-alpha to the pathogenesis of diarrhea in these diseases, ion transport of human distal colon was studied in the Ussing chamber in vitro. Serosal addition of TNF-alpha increased short-circuit current (Isc) of partially stripped tissues in a dose-dependent manner. Maximum Isc increase of 1.8 +/- 0.2 mumol.h-1.cm-2 was reached after 60 +/- 9 min at 200 ng/ml TNF-alpha. Bidirectional tracer flux measurements revealed that TNF-alpha induced an increase in 36 Cl serosal-to-mucosal flux, a decrease in 36Cl- mucosal-to-serosal flux, and a slight increase in K+ secretion indicated by an increased secretory 86Rb net flux. In the highly differentiated colonic epithelial cell line HT-29/B6, TNF-alpha had no effect on Isc, suggesting a mediation step located in the subepithelium. This supposition was supported by measurements on totally stripped human tissues, since removal of subepithelial layers by total stripping reduced the TNF-alpha effect by 40%. Experiments with tetrodotoxin (10(-6)M) indicated that the TNF-alpha effect was not mediated by the enteric nervous system. The specific 5-lipoxygenase blocker ICI-230487 (5 x 10(-8)M) also had no effect on TNF-alpha action. In contrast, inhibition of cyclooxygenase by indomethacin (10(-6)M inhibited the effect of TNF-alpha. Radioimmunoassay of prostaglandin E2 (PGE2) in the serosal bathing solution revealed an increase in PGE2 production/release after addition of TNF-alpha, which paralleled the Isc response. We conclude that TNF-alpha changed Cl- and K+ transport toward secretion in human colon. This effect was mediated by PGE2 produced by subepithelial cells. Thus TNF-alpha could be a mediator of diarrhea during intestinal inflammation, e.g., in IBD and HIV infection.

Stool viruses, coinfections, and diarrhea in HIV-infected patients. Berlin Diarrhea/Wasting Syndrome Study Group.

To examine the prevalence of stool viruses and their role in the pathogenesis of diarrhea in HIV infection, we evaluated biopsies and repeated stool samples of 256 HIV-infected patients undergoing diagnostic endoscopy because of diarrhea (n = 136) or other symptoms (n = 120) for bacterial, protozoal, and viral enteropathogens. In 70% of the patients with diarrhea, at least one potential enteropathogen was detected. Stool virus was detected by electron microscopy in 17% (44 of 256), adenovirus in 6.6% (17 of 256), and coronavirus in 11.3% (29 of 256) of the patients. Adenovirus and coronavirus were detected more frequently in patients with diarrhea than in patients without diarrhea [adenovirus 10% (13 of 136) vs. 3.3% (4 of 120), p = 0.0129; coronavirus 15% (21 of 136) vs. 6.6% (8 of 120), p = 0.0142]. Sixty-one percent of patients harboring stool virus were coinfected by another enteropathogen. Pathogens other than stool virus were detected more frequently in patients harboring adenovirus (82%) than in patients without stool virus (48%, p < 0.025). Adenovirus and coronavirus are frequently detected in stools of HIV- infected patients and may contribute to diarrhea. Adenovirus infection may facilitate the occurrence of other intestinal pathogens. Due to frequent coinfections, detection of stool viruses reduces the rate of diarrhea of unknown origin only by approximately 5%.

Role of Candida in indirect pathogenesis of antibiotic associated diarrhoea in infants.

One hundred and thirty seven isolates of Candida species were isolated from antibiotic associated diarrhoea cases and were examined to study the role of Candida in the pathogenesis of diarrhoea in infants. The quantitative estimation of yeast population by simple gram stain smear revealed more than 70% of the cases had 3+ score. The isolates further screened for detection of beta-lactamases. Among the isolated Candida sp, beta-lactamases was secreted by C. albicans, C. tropicalis, C. krusei and C. parapsilosis. Further, 46% of the Candida isolates were found to be produced 741-1110 mU/ml of beta-lactamases, suggesting that these enzyme would inactivate penicillin group of drugs and cause failure in the therapy directed against other diarrhoegenic bacteria.

The role of somatostatin analogues in the treatment of refractory diarrhoea.

Octreotide inhibits intestinal motility and secretions of the gastro-intestinal tract and pancreas and mediators of diarrhoea and so is very useful in managing refractory diarrhoea. It is safe and effective in 75-80% of the 10-20% of cancer chemotherapy patients who develop severe diarrhoea, and is useful in the management of persistent diarrhoea associated with neuroendocrine tumours, particularly VIPoma and carcinoid tumours, congenital microvillus atrophy, some patients with the short bowel syndrome (giving them a reduced need for intravenous fluids), and AIDS-related diarrhoea that does not respond to antibiotics or conventional anti-diarrhoeal drugs. Some studies suggest a 50% effectiveness in graft-versus-host disease. Preliminary studies suggest that octreotide is also of value in persistent diarrhoea caused by neuromuscular disorders of the gut, particularly diabetes mellitus and systemic sclerosis, suggesting that it may have wider application in the future. Octreotide may prove useful as a tool for studying the pathogenesis of diarrhoea of diverse aetiologies, particularly those associated with disturbances of intestinal motility, such as irritable bowel syndrome.

Pathogenesis of Diarrhoea in Medullary Thyroid Carcinoma

Pathogenesis of Diarrhoea in Medullary Thyroid Carcinoma

Diarrhea and the patient receiving enteral feedings: a multifactorial problem.

Diarrhea is often considered an inevitable consequence of enteral tube feeding. The pathogenesis of diarrhea in patients receiving enteral feeding is not well understood, but it has been attributed to hypoalbuminemia, bacterial contamination of formula, characteristics of enteral feeding formula, and concomitant drug therapy. The purpose of this article is to review research regarding the etiology and treatment of diarrhea in patients receiving enteral feeding and to identify implications for nursing practice and future research.

Characterization of the C-terminal domains of intimin-like proteins of enteropathogenic and enterohemorrhagic Escherichia coli, Citrobacter freundii, and Hafnia alvei

Surface proteins called intimins (Int), which are homologous to the invasin protein (Inv) of Yersinia spp., play a role in inducing brush border damage, termed attachment and effacement, which follows infection by enteropathogenic and enterohemorrhagic Escherichia coli, Citrobacter freundii biotype 4280, and Hafnia alvei. Maltose-binding protein (MBP) fusions containing the C-terminal 280 amino acids of Int-like proteins of strains of enteropathogenic E. coli, enterohemorrhagic E. coli, H. alvei, and C. freundii biotype 4280 and of Yersinia pseudotuberculosis Inv were constructed and purified. The 3' end of the gene for the H. alvei Int-like protein was sequenced and showed homology to corresponding regions of other Int-encoding genes. Binding of MBP-Int-like and MBP-Inv fusion proteins to HEp-2 cells was demonstrated by immunofluorescence microscopy and by fluorescence-activated cell sorting. MBP-Inv induced attachment and spreading of HEp-2 cells to plastic-coated wells, but MBP-Int-like fusion proteins did not. Preincubation of HEp-2 cells with MBP-Inv, but not with MBP-Int-like fusion proteins, inhibited MBP-Inv-induced cell attachment. Fixed staphylococci and fluorescent polymer microspheres coated with both MBP-Int-like and MBP-Inv fusion proteins showed enhanced adhesion to HEp-2 cells. These fusion proteins will facilitate studies of the role of intimin in the pathogenesis of diarrhea associated with members of the family Enterobacteriaeceae that induce attachment and effacement.

Malnutrition and infection

In individual children in developed countries it is possible to follow a sequence of infection of the gastrointestinal tract leading to chronic diarrhoea which, if it long persists, may in turn lead to undernutrition. Both in individuals and epidemiologically in developing countries it is, by contrast, often difficult to be certain whether infection precedes under-nutrition or vice versa. Chronic diarrhoea is heterogeneous and aetiology varies from community to community. Unlike acute diarrhoea, for which there is highly effective unitary therapy (oral rehydration therapy), diverse therapies are required for chronic diarrhoea based on specific diagnoses and so render community strategies difficult. The importance of adequate calorie intake is emphasized but when there is intolerance to food ingested this is counter-productive. The relative importance of post-infective food intolerance remains controversial and in many communities is unknown. Increasing emphasis is now given to the role of infection in pathogenesis of diarrhoea and malnutrition e.g. the acquired immune deficiency syndrome and Helicobacter pylori. Hospital-based case studies including small intestinal biopsy in individual communities, by virtue of an ‘iceberg effect’, may prove useful for insights into aetiology and pave the way for interventions e.g. antibiotics or dietary therapy.

Subepithelial collagen table thickness in colon specimens from patients with microscopic colitis and collagenous colitis

Microscopic colitis and collagenous colitis are similar conditions that are differentiated by the presence or absence of subepithelial collagen table thickening. To better understand the relationship between these two disorders and the role of collagen table thickening in the pathogenesis of diarrhea, colonic mucosal biopsy specimens from 24 patients with microscopic or collagenous colitis and 9 control subjects were analyzed using a computerassisted morphometric method to evaluate the average thickness of the subepithelial collagen table. The collagen table thickness in colitis patients taken together formed a multimodal rather than a unimodal distribution. There was no tendency for collagen table thickening to increase with age or with duration of symptoms. In general, the types and distribution of inflammatory cells were similar in patients with normal and thickened collagen tables. Stool weight correlated with lamina propria cellularity but not with collagen table thickening. The multimodal distribution of collagen table thickening and the lack of correlation with age, duration of symptoms, or inflammation suggest that microscopic colitis and collagenous colitis are discrete conditions, although the inflammatory changes in the two conditions are similar. Moreover, because stool weight correlates with lamina propria cellularity but not with collagen table thickening, diarrhea probably is caused by the inflammatory changes and not by collagen table thickening per se.

Conventional screening for enteropathogenic Escherichia coli in the UK. Is it appropriate or necessary?

Enteropathogenic Escherichia coli (EPEC) is a well-recognized cause of infantile diarrhoea in the developing countries. In the developed countries, however, the incidence of EPEC associated outbreaks has dramatically declined. The last major outbreak in the UK was reported in 1980. This paper reviews the recent advances in the field of pathogenesis of diarrhoea caused by EPEC and questions the need to screen routinely for EPEC by conventional serological methods used in clinical microbiology laboratories in the UK.

Carbohydrate malabsorption in the pathogenesis of diarrhea during postoperative enteral feeding

Carbohydrate malabsorption in the pathogenesis of diarrhea during postoperative enteral feeding

Structural and functional changes in rabbit ileum by purified extracellular phospholipase a ofSalmonella newport

As phospholipases of Salmonella species may play a role in the pathogenesis of gastrointestinal tract diseases. Salmonella newport, the causative agent of infantile diarrhoea was examined for the production of phospholipase. The enzyme was purified by gel filtration chromatography and was found to be a protein of molar mass ranging from 43 to 67 kDa. The purified enzyme alone or in combination with organisms, produced both structural and functional changes in rabbit ileum, contributing towards pathogenesis of diarrhoea due to this organism.

Verotoxic Escherichia coli in Human Disease

SummaryVerotoxin‐producing E. coli (most frequently E. coli 0157) have been implicated in the pathogenesis of diarrhea, hemorrhagic colitis, hemolytic uremic syndrome and thrombotic thrombocytopenic purpura. Cattle, meat products, and other sources have been found to harbor these organisms. Isolation of E. coli 0157:H7 on MacConkey‐sorbitol agar is diagnostic, yet the bacteria are difficult to detect after the first week of infection. Enzyme linked immunosorbent assays (ELISAs) can detect verotoxin in fecal filtrates in the absence of viable bacteria. Serologic evidence has also been used to support the diagnosis of verotoxin‐associated infection. Evidence supporting the etiologic role of different verotox‐ins is reviewed. Treatment remains supportive since the use of antibiotics and antimotility agents can lead to poorer outcomes. Recommendations for prevention are presented.

Verotoxic Escherichia coli in Human Disease

Verotoxin-producing E. coli (most frequently E. coli O157) have been implicated in the pathogenesis of diarrhea, hemorrhagic colitis, hemolytic uremic syndrome and thrombotic thrombocytopenic purpura. Cattle, meat products, and other sources have been found to harbor these organisms. Isolation of E. coli O157:H7 on MacConkey-sorbitol agar is diagnostic, yet the bacteria are difficult to detect after the first week of infection. Enzyme linked immunosorbent assays (ELISAs) can detect verotoxin in fecal filtrates in the absence of viable bacteria. Serologic evidence has also been used to support the diagnosis of verotoxin-associated infection. Evidence supporting the etiologic role of different verotoxins is reviewed. Treatment remains supportive since the use of antibiotics and antimotility agents can lead to poorer outcomes. Recommendations for prevention are presented.