Myoelectric effects of Clostridium difficile: motility-altering factors distinct from its cytotoxin and enterotoxin in rabbits.

Clostridium difficile is a bacterium that causes antibiotic-associated pseudomembraneous enterocolitis. This bacterium produces a cytotoxin that induces tissue culture assay positivity and an enterotoxin that causes in vivo mucosal injury. In previous studies we have described two altered myoelectric patterns in response to certain diarrheagenic organisms in an in vivo rabbit model. The first pattern was called the migrating action potential complex and is associated with noninvasive agents; the second pattern was called repetitive bursts of action potentials and is characteristic of invasive or cytolytic agents. In this study, we evaluated the effects of purified cytotoxin (2.5-3.75 micrograms) and enterotoxin (140 micrograms) from C. difficile on the myoelectric activity in isolated ileal loops in New Zealand White rabbits. These observations in myoelectric activity were correlated with the results of similar studies by using the crude culture filtrates from C. difficile, or the products of Amicon XM50 filtration of its culture supernatant resulting in a high molecular weight product (0.3 mg protein/ml) and a low molecular weight product (0.57 mg protein/ml). Monopolar silver-silver chloride electrodes were used to record all myoelectric activity for an 8-h period. The animals were then killed, and tissue obtained from the ileal loops was histologically evaluated. Crude culture filtrates of C. difficile induced 7.0 migrating action potential complexes/hour and 6.8 repetitive bursts of action potentials/hour. Saline controls induced no migrating action potential complexes and 0.1 repetitive bursts of action potentials/hour. The high molecular weight filtration product obtained from the culture supernatant of C. difficile induced significantly more repetitive bursts of action potentials (41.1/h) than all agents studied. The purified cytotoxin or enterotoxin induced no migrating action potential complex activity and minimal repetitive bursts of action potential activity (0.9/h and 0.6/h, respectively). These values were not different from the saline controls; however, only the enterotoxin and the high molecular weight filtration product caused mucosal damage. These studies suggest that C. difficile produces a heat-labile substance or substances that alter the motility of the small intestine independent of the proteins responsible for in vivo tissue damage and cytotoxin assay positivity.