Rapid detection of Clostridium difficile toxin in human feces.

Fifty fecal specimens were tested by three methods, bacterial isolation, counterimmunoelectrophoresis, and tissue culture, for Clostridium difficile and its toxin. Ten specimens (20%) were positive by all three methods. An additional eight specimens were toxin positive only by counterimmunoelectrophoresis. Although counterimmunoelectrophoresis and tissue culture are of equivalent sensitivity, the additional dilution necessary for tissue culture assay may be critical when only small concentrations of toxin are present.