Comparison of five cultural procedures for isolation of Clostridium difficile from stools

Several procedures have been described for the culture of Clostridium difficile from stool specimens. The goal of this study was to determine the effectiveness of five of these methods for the isolation of C. difficile from feces of patients suspected of having C. difficile-associated illness. A total of 564 stool specimens were cultured by using heat shock, ethanol treatment (ET), and direct plating on Carr-Scarborough cycloserine-cefoxitin-fructose agar (CCFA) with horse blood (C/S medium), BBL CCFA medium, and Remel C. difficile agar. Cytotoxin assays were performed on all specimens. A total of 113 specimens (20%) were positive for C. difficile by one or more methods. The numbers of positive cultures by using heat shock, ET, and direct plating on C/S medium, BBL CCFA medium, and Remel C. difficile agar were 79 (70%), 89 (79%), 91 (81%), 79 (70%), and 52 (46%), respectively. We concluded that ET and direct plating on C/S medium were the most effective procedures for isolating C. difficile from stool specimens and found significant variation in the performance of modified CCFA from different manufacturers.