Identification of Clostridium difficile in stool specimens by culture-enhanced gas-liquid chromatography.

We have developed a sensitive and specific method for the identification of Clostridium difficile in stool specimens based on the detection of metabolic breakdown products of the organism by gas-liquid chromatography after incubation of stool samples in a selective broth medium containing cefoxitin. Use of this approach to test samples from two different populations of patients at separate medical centers showed this method to be superior to plate cultures or cytotoxin testing alone for both populations. The combined results from the two patient populations showed that 225 of 226 confirmed isolates were identified correctly, resulting in a sensitivity of 99.6% and a specificity of 99.0%. This method eliminates the delay caused by subculturing for tests requiring a pure isolate. The culture phase amplifies even low numbers of C. difficile in fecal samples (due to low in vivo concentrations or delayed transport) and thus increases sensitivity. Other advantages include the ability to detect C. difficile in the mixed flora of the stool and the ability of most clinical laboratories to use this procedure. Given the complexities of the detection of C. difficile toxins and the increasing importance of this organism as a nosocomial agent, culture-based methods remain the preferred approach to screening and routine workup for cases of diarrhea.