Clostridium difficile infection (CDI) is responsible for 250,000 infections and 14,000 deaths annually. High rates of treatment failure, recurrent infections, and potential for antibiotic resistance are all evidence that new and effective treatments for CDI are needed. A potential treatment for CDI is Auranofin, which disrupts the selenoproteins used for anaerobic metabolism in C. difficile. The aim of this study is to assess the potential of Auranofin as a treatment for CDI.
Growth assays were performed to investigate the effect of Auranofin on C. difficile strain CD01 (ribotype 014) growth (OD600), cell viability, sporulation. Effects on toxin activity were tested by Cell Cytotoxicity Assay. Controls for these experiments were untreated cultures (negative), ethanol treated cultures (diluent) and metronidazole (current treatment).
Auranofin inhibits the growth of C. difficile at concentration of 50µM when compared to the control (p<0.0001). No viable cells were recovered from the Auranofin treated cultures, indicating that Auranofin is bactericidal against C. difficile. Sporulation assays yielded less spores from Auranofin treated cultures that the negative and diluent control. Cell cytotoxicity assays showed that Auranofin treated cultures had less cytotoxic activity against vero cells than the no treatment control (p<0.0001) but is not significantly different to the ethanol control. There was no significant difference between Auranofin and Metronidazole with regards to C. difficile growth, cell viability or sporulation.
The bactericidal activity and pharmacokinetics of Auranofin make it good candidate for a CDI treatment. Auranofin may also be narrow spectrum, with just 14% of bacteria utilizing selenoproteins. Further experiments will compare Auranofin to the current treatment Vancomycin, and assess the effect of Aurnaofin on hypervirulent ribotype 027. Auranofin will then be trialled in a CDI and recurrent CDI mouse model, focusing on treatment of disease, prevention of recurrent disease, disease severity and effects on the intestinal microbiota.