Diagnosis of Clostridium difficile infection by toxigenic culture and PCR assay

Background and Objectives: Clostridium difficile is responsible for 15-25% of nosocomial antibiotic associated diarrhea (AAD) cases and all cases of pseudomembranous colitis. C. difficile has two major virulence factors, toxin A (enterotoxin) and toxin B (cytotoxin). The aim of this study was to determine the frequency of C. difficile strains in patients with diarrhea in Babol' hospitals with toxigenic culture and PCR assay. Materials and Methods: One hundred stool specimens were taken from diarrheal patients in hospitals of the city of Babol. All patients had a history of antibiotic use. The samples were cultured on CCFA medium. In the next stage, toxigenic culture was performed for isolated C. difficile strains. Then, PCR assay was used to identify gdh, tcdA and tcdB genes among isolated C. difficile strains. Results: From the 100 stool samples, eight (8%) samples were positive in C. difficile culture. In toxigenic culture, two (2%) of these strains had cytopathic effects on Vero cells. All eight strains had the gdh gene. This gene is specific for C. difficile. Two strains that had cytopathic effects on toxigenic culture were positive for toxin genes. Conclusion: The frequency of toxigenic strains in different parts of the world is variable, and needs to be continually investigated. In the present study, the PCR method had a good correlation with toxigenic culture. Thus, it can replace the laborious and costly cell culture method.