Resistance properties among different Clostridioides difficile isolates

The rod-shaped, motile and obligate anaerobic bacterium Clostridioides difficile occurs ubiquitously in the environment and colonizes the gastrointestinal tract of mammals. As a leading causative agent of antibiotic-associated diarrhea worldwide, it is particularly relevant in clinical settings. The pathogenicity of C. difficile is based on the formation and secretion of toxins and the associated damage to the intestinal epithelial tissue. If the C. difficile infection (CDI) progresses severely, the consequences for the patient can be fatal. Treating CDI is challenging due to C. difficile's ability to form metabolic dormant endospores, which leads to the risk of reinfection.

Since the first description in the 1930s, numerous isolates have been characterized. Common protocols recommend heat or ethanol shock during sample preparation, using the endospore's resistance for isolating purposes. It became apparent that both, the vegetative cells and the corresponding endospores of several isolates react differently to certain treatments. As a result, the isolation conditions used to monitor C. difficile populations might not reflect the actual situation. To address this issue, a panel of C. difficile isolates were tested regarding their resistance properties over different exposure times applying a plating procedure. Here, defined concentrations of vegetative cells as well as endospores were used to determine classical characterization parameters based on the inactivation kinetics. This knowledge provides information to improve isolation and enrichment strategies to obtain a better understanding of the environmental distribution of C. difficile populations.