Evaluation of a ChromID C. difficile Agar for the Isolation of Clostridium difficile

Background: Clostridium difficile is the main etiologic agent of antibiotic-associated diarrhea and the most common cause of hospital-acquired diarrhea. Recently, the incidence of C. difficile infections (CDI) has increased and new highly virulent C. difficile strains have emerged. Therefore, accurate and rapid diagnosis is needed. We compared the results of using chromID C. difficile (chromID CD, bioMerieux, France) with the conventional C. difficile Selective Agar (CDSA; BD, USA) for the isolation of C. difficile. Methods: A total of 738 stool specimens of suspected CDI patients at the Severance Hospital from July to August 2011 were inoculated onto CDSA. Among them, 104 stool specimens revealed colonies on CDSA that were then re-inoculated onto chromID CD. The stool samples were stored at −20 o C until the time of the re-inoculation. Cultured agars were interpreted after 24 hrs and 48 hrs, respectively. Species identification was performed on the basis of colony characteristics on agar plates as well as the ATB 32A system (API System SA, France). Results: The recovery rates of CDSA and chromID CD were 30.1% and 77.5% after 24 hrs, and 77.5% and 98.6% after 48 hrs, respectively. All of the C. difficile isolates were recovered as typical gray/black colonies on chromID CD. Conclusion: The performance of chromID CD for the isolation of C. difficile was better than that of conventional CDSA. The chromID CD could provide easy and sensitive detection of C. difficile even after 24hrs of incubation. (Korean J Clin Microbiol 2012; 15:88-91)