Clostridium difficile toxin B is more potent than toxin A in damaging human colonic epithelium in vitro (original) (raw)
1995, Journal of Clinical Investigation
Toxin A but not toxin B, appears to mediate intestinal damage in animal models of Clostridium difficile enteritis. The purpose of this study was to investigate the electrophysiologic and morphologic effects of purified C. difficile toxins A and B on human colonic mucosa in Ussing chambers. Luminal exposure of tissues to 16-65 nM of toxin A and 0.2-29 nM of toxin B for 5 h caused dose-dependent epithelial damage. Potential difference, short-circuit current and resistance decreased by 76, 58, and 46%, respectively, with 32 nM of toxin A and by 76, 55, and 47%, respectively, with 3 nM of toxin B, when compared with baseline (P < 0.05).
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Digestive Diseases and Sciences, 2005
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Effects of purified Clostridium difficile toxin A on rabbit distal colon
Gastroenterology, 1995
Background & Aims: Antibiotic-associated pseudomembranous colitis in humans is caused by proliferation of Clostridium difficile, which elaborates an enterotoxin toxin A that causes epithelial damage and altered motility in rabbit small intestine. The aim of this study was to assess the effects of toxin A on rabbit distal colonic motility and to relate this to histological damage and inflammatory mediator production. Methods: Two hundred micrograms per milliliter of toxin A was placed in a distal colonic loop in anesthetized rabbits, and myoelectric activity was recorded for the following 7 hours. The colon was histologically evaluated and assayed for eicosanoid production. The effects of toxin A on longitudinal and circular muscle were also assessed in vitro. Results: Beginning I hour after instillation, toxin A caused a significant increase in the number of spike bursts without altering slow wave frequency; this was associated with an increase in mucosal neutrophils and increased production of prostaglandin E2 and leukotrienes B4 and C4/D4/E 4. Seven hours after administration of toxin A, mediator levels and myoelectric activity remained increased but significant mucosal damage was now also present. Toxin A did not affect longitudinal or circular muscle in vitro. Conclusions: C. difficile toxin A caused a significant neutrophil infiltration and an increased myoelectric activity before producing mucosal damage. The myoelectric effect may be indirect, resulting from the production of motility-altering arachidonic acid metabolites.
Effect of toxin A and B of Clostridium difficile on rabbit ileum and colon
Gut, 1986
The effect of purified toxin A and partially purified toxin B on rabbit ileum and colon was investigated. Toxin A caused tissue damage which was followed by permeability changes and fluid accumulation in both tissues. Toxin A did not increase the permeability of the colon to the extent observed for ileum; secreted fluid contained less protein of plasma origin. Toxin B had no effect on either tissue. Secretory a-id tissue damaging properties of crude C difficile toxins were found. to be due to toxin A.
The role of toxin A and toxin B in Clostridium difficile infection
Nature, 2010
Clostridium difficile infection is the leading cause of healthcareassociated diarrhoea in Europe and North America 1,2 . During infection, C. difficile produces two key virulence determinants, toxin A and toxin B. Experiments with purified toxins have indicated that toxin A alone is able to evoke the symptoms of C. difficile infection, but toxin B is unable to do so unless it is mixed with toxin A or there is prior damage to the gut mucosa 3 . However, a recent study indicated that toxin B is essential for C. difficile virulence and that a strain producing toxin A alone was avirulent 4 . This creates a paradox over the individual importance of toxin A and toxin B. Here we show that isogenic mutants of C. difficile producing either toxin A or toxin B alone can cause fulminant disease in the hamster model of infection. By using a gene knockout system 5,6 to inactivate the toxin genes permanently, we found that C. difficile producing either one or both toxins showed cytotoxic activity in vitro that translated directly into virulence in vivo. Furthermore, by constructing the first ever double-mutant strain of C. difficile, in which both toxin genes were inactivated, we were able to completely attenuate virulence. Our findings re-establish the importance of both toxin A and toxin B and highlight the need to continue to consider both toxins in the development of diagnostic tests and effective countermeasures against C. difficile.
Clostridium difficile toxin B is an inflammatory enterotoxin in human intestine
Gastroenterology, 2003
Background & Aims: Clostridium difficile causes antibiotic-associated diarrhea and pseudomembranous colitis, diseases afflicting millions of people each year. Although C. difficile releases 2 structurally similar exotoxins, toxin A and toxin B, animal experiments suggest that only toxin A mediates diarrhea and enterocolitis. However, toxin A-negative/toxin B-positive strains of C. difficile recently were isolated from patients with antibiotic-associated diarrhea and colitis, indicating that toxin B also may be pathogenic in humans. Methods: Here we used subcutaneously transplanted human intestinal xenografts in immunodeficient mice to generate a chimeric animal model for C. difficile toxin-induced pathology of human intestine. Results: We found that intraluminal toxin B, like equivalent concentrations of toxin A, induced intestinal epithelial cell damage, increased mucosal permeability, stimulated interleukin (IL)-8 synthesis, and caused an acute inflammatory response characterized by neutrophil recruitment and tissue damage. Laser capture microdissection and real-time quantitative reverse-transcription polymerase chain reaction (RT-PCR) showed that intestinal epithelial cell-specific IL-8 gene expression also was increased significantly after luminal exposure to C. difficile toxins in vivo.
Clinical and Experimental Immunology, 2008
Summary Clostridium difficile induces mucosal inflammation via secreted toxins A and B and initial interactions between the toxins and intestinal epithelial cells (which lead to loss of barrier function) are believed to be important in disease pathogenesis. Secreted toxin-specific antibodies may inhibit such interactions. Using the Caco-2 epithelial cell line, we have investigated the use of an anti-toxin A monoclonal antibody (ATAA) in providing protection against toxin A-mediated disruption of epithelial barrier function (assessed by measurement of transepithelial electrical resistance and luminal to basolateral flux of labelled dextran). In contrast to free antibody, ATAA conjugated to sepharose beads was more effective in neutralizing the activity of purified toxin A. Sepharose bead-conjugated ATAA was subsequently used to investigate the contribution of toxin A in epithelial injury mediated by C. difficile supernatant samples (containing toxins A, B and other products). Loss of...
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