Rapid detection of toxigenic Clostridium difficile in fecal samples by magnetic immuno PCR assay.

Rapid detection of toxigenic Clostridium difficile in fecal samples was accomplished with the magnetic immuno PCR assay (MIPA). Elaborate DNA extraction techniques were unnecessary. First, we generated a mouse monoclonal antibody (MAb) reactive with only C. difficile, Clostridium sordellii, and Clostridium bifermentans. Then, magnetic beads were coated with the MAb, incubated with fecal samples to allow binding with C. difficile, extracted from the stool with a magnet, and processed in the PCR with primers specific for the toxin B gene. After optimizing MIPA by raising the number of PCR cycles from 35 to 40 and adding Chelex 100 to the PCR mixture, we found a sensitivity of 96.7%, a specificity of 100%, a positive predictive value of 100%, and a negative predictive value of 94.1% when compared with the culture of cytotoxic C. difficile from fecal samples. MIPA is a rapid, easy, and sensitive PCR method for demonstrating the presence of toxigenic C. difficile in stool samples and avoids the disadvantage of elaborate extraction of DNA from fecal samples.