Comparison of culture and isolation methods for Clostridioides difficile and other anaerobes from stool samples in a routine microbiological laboratory practice

Objective. To improve stool sample culture and isolation of anaerobic flora, including Clostridioides difficile in the routine microbiological laboratory practice at the children’s oncology hospital. Materials and Methods. A total of 517 stool samples collected from patients in children’s oncology hospital from 2013 to 2015 were studied. All samples were analyzed by ELISA for C. difficile toxins and by culture according to dedicated 5 schemes for isolation of anaerobic bacteria, including C. difficile. Statistical significance of differences in isolation rates between the studied groups (culture schemes) was assessed by Pearson test. Results. Culture in liver broth and covering with technical agar followed by culture on anaerobic agar yielded 100% isolation rate of toxigenic C. difficile strains. This culture scheme is also suitable for isolating concomitant anaerobic flora: non-toxigenic C. difficile strains, Clostridium perfringens, other Clostridia spp. and Bacteroides spp. Conclusions. Use of the liquid accumulation medium and covering with technical agar make it possible to isolate anaerobic flora from stool samples and increase an isolation rate of toxigenic C. difficile strains to 100% of ELISA-positive samples.