ABSTRACT
Objective To evaluate the clinical application value of Xpert detection system of Clostridium difficile (C.difficile).Methods A total of 43 stool specimens from the patients with diarrhea were collected,and C.difficile in stool specimens were detected by the Xpert detection system,the toxigenic culture method,and the toxin detection method which detected the toxin of C.difficile by VⅥDAS automatic analyzer after anaerobic culture,respectively.The analytic performance of Xpert detection system was evaluted based on the toxigenic culture method as the gold standard.Meanwhile,the consistency of the results from different detection methods was compared.The ribotype 027 strain (ATCC BAA-1870) simulating the stool specimen was further used to verify the Xpert detection system.Results Based on the gold standard of the toxigenic culture method,the sensitivity,specificity,positive predictive value and negative predictive value of the Xpert detection system were 90.9％,93.8％,83.3％ and 96.8％,respectively.The Kappa values for the consistency between the Xpert detection system and the toxigenic culture method or the toxin detection method were 0.822 (P ＜ 0.05) and 0.419 (P ＜ 0.05),respectively.Moreover,the ribotype 027 strain simulating the stool specimen was verified by the Xpert detection system successfully.Conclusion The Xpert detection system may rapidly and accurately detect the C.difficile in stool specimens,especially the ribotype 027 strain with high toxicity.
ABSTRACT
We evaluated the performance of a new chromogenic medium for detection of Clostridium difficile, chromID C. difficile agar (CDIF; bioMerieux, France), by comparison with BBL C. difficile Selective Agar (CDSA; Becton Dickinson and Company, USA). After heat pre-treatment (80degrees C, 5 min), 185 diarrheal stool samples were inoculated onto the two media types and incubated anaerobically for 24 hr and 48 hr for CDIF and for 48 hr and 72 hr for CDSA. All typical colonies on each medium were examined by Gram staining, and the gram-positive rods confirmed to contain the tpi gene by PCR were identified as C. difficile. C. difficile was recovered from 36 samples by using a combination of the two media. The sensitivity with CDIF 48 hr was highest (100%) and was significantly higher than that with CDIF 24 hr (58.3%; P<0.001), because samples with a low burden of C. difficile tended to require prolonged incubation up to 48 hr (P<0.001). The specificity of CDIF 24 hr and CDIF 48 hr (99.3% and 90.6%, respectively) was significantly higher than that of CDSA 48 hr and CDSA 72 hr (72.5% and 67.1%, respectively; P<0.001). CDIF was effective for detecting C. difficile in heat-pretreated stool specimens, thus reducing unnecessary testing for toxin production in non-C. difficile isolates and turnaround time.