Diagnosis and monitoring of Clostridium difficile infections with the polymerase chain reaction.

Toxigenic Clostridium difficile is the etiologic agent of pseudomembranous colitis. We have developed an assay system for the rapid direct detection of toxigenic C. difficile in human stool samples. After DNA extraction, polymerase chain reaction (PCR) amplification is undertaken with primers targeting specific sequences in the C. difficile 16S rRNA gene. Next, toxigenic strains of C. difficile are distinguished from nontoxigenic strains by PCR amplification of toxin A and/or B gene sequences. This study included 12 patients with C. difficile colitis, seven of whom had clinical relapses after discontinuation of vancomycin therapy. We detected toxigenic C. difficile in stools from four (57%) of these seven patients before relapse--at a time when no toxin B was detectable in stools and results of anaerobic culture were negative. The PCR assay is 100-fold more sensitive than anaerobic culture methods. The course of the infection in one patient (both during and after therapy) was monitored by the PCR technique. The multigene analysis approach permitted the detection of colonization with a nontoxigenic strain when this patient's relapses had cleared. This clinically applicable assay allows earlier detection of infection with toxigenic C. difficile. The result is more timely therapeutic intervention.