Background: Clostridium difficile  infection (CDI) has become one of the most important factors threatening human health, and about 20– 30% antibiotic-related diarrhea cases and almost all pseudomembranous enteritis cases are related to CDI. The high recurrence of Clostridium difficile (C. difficile)  and the emergence of drug resistance make clinical treatment of CDI difficult. Therefore, there is an urgent need to develop a non-antibiotic-alternative therapy against CDI. Gold nanoclusters (AuNCs) can better interact with bacteria due to its ultrasmall size. The aim of the present study was to explore whether AuNCs could be used as an antibacterial agent to kill C. difficile .
Methods: AuNCs and C. difficile  were co-cultivated in an anaerobic atmosphere to evaluate the bactericidal effect of AuNCs. The bacterial growth rate was estimated by using two concentrations of AuNCs (50 and 100 μM). The damage of AuNCs to C. difficile  is detected by SYTOX Green staining methods and SEM image analysis. The mechanism of AuNCs on C. difficile  was explored by reactive oxygen species (ROS) detection. The toxic effect of AuNCs on human cells was evaluated by MTT method.
Results: AuNCs (100 μM) killed C. difficile  drastically. AuNCs increased the release of ROS by about 5 fold and destroyed the membrane integrity of C. difficile  cells without causing significant toxic effect on human cells.
Conclusion: AuNCs showed great potential as an alternative to traditional antibiotics in killing C. difficile  and may prove to be an alternative to treat CDI.
Keywords: Clostridium difficile , antibacterial effect, gold nanoclusters, reactive oxygen species