Effect of toxin A and B of Clostridium difficile on rabbit ileum and colon.

Abstract

SUMMARY 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.Clostridium difficile is now known to be the primary cause of antibiotic associated pseudomembranous colitis.1 2 The organism produces four toxins of possible relevance in the pathofenesis of the disease: an enterotoxin (toxin A),3 a cytotoxin (toxin B),3 4 a motility altering factor5 and a recently described labile toxin which causes clear fluid accumulation in rabbit ileal loops.6 In contrast with cholera and Escherichia coli heat labile toxins which induce fluid accumulation with no tissue damage,7 8 toxin A of C difficile causes fluid accumulation with mucosal damage in several animal models: rabbit ileal loop test,9 10 hamster ileal loop9 and hamster caecal loop.9 10 Toxin A is also lethal to mice and causes increased vascular permeability in guinea pig skin.9 Thus toxin A appears to have a mode of action different to that of cholera or E coli heat labile toxins because it causes tissue damage in combination with fluid secretion. Toxin B does not cause fluid accumulation in rabbit ileal loops9 11 or hamster ileal loops. 12 There are discrepancies, however, as to its tissue damag' -g properties:Taylor et a19 report that only limited histological damage is caused to mucosal epithelium of hamster caeca whereas Libby et al'2 showed substantial damage. Toxin B is cytotoxic for a variety of cell lines in vitro but the relevance of this observation to fluid secretion in the intestine is unclear.

Biological mode of action of Clostridium difficile toxin A: a novel enterotoxin

“…Approximately 30 pg of the added 50 pg of toxin A had been taken up by this time (table I). Titration studies (Mitchell et al, 1986) had previously indicated that as little as 3 pg of toxin A inoculated into the lumen of 6-cm ileal loops can provoke fluid accumulation by 12 h; 3 pg of toxin A was associated with the tissue by < 5 min in these toxin uptake experiments, but did not induce fluid accumulation at 12 h. These data are, at first sight, difficult to interpret and are considered further in the discussion.…”

“…Similar structures have been found in a re-interpretation of our original material : in fig. 6 of the paper by Mitchell et al (1986) this membranous structure did not reproduce clearly.…”

“…Ileal and colonic loops were constructed as previously described (Mitchell et al, 1986), with the following modifications. The colon was ligated approximately 25 cm distal to the caecum-colon junction; 20 ml of saline was introduced into the lumen at the ligation point and was washed back up the colon and into the caecum.…”

The effects of Clostridium difficile crude toxins and purified toxin A on stripped rabbit ileal mucosa in Ussing chambers

“…Third, it is our view that toxin A, which we have shown to be of overriding importance in the causation of tissue damage and fluid accumulation in rabbit experimental systems (Mitchell et al, 1986) could be responsible. Such a view is confirmed by Lyerly et al (1985) who showed that toxin A was responsible for the enteric effects of toxic crude culture filtrates administered orogastrically to hamsters.…”

“…We recently discussed (Mitchell et al, 1986) the range and properties of known toxins produced by C. dzficile that are of possible relevance in the causation of diarrhoea1 disease. These include (1) toxin A (enterotoxin), and (2) toxin B (cytotoxin), on the nature and properties of which there is a considerable body of evidence from several laboratories.…”