Curcumin: A natural derivative with antibacterial activity against Clostridium difficile

•This study proposed curcumin, a bioactive extract of turmeric, as a potential stand-alone natural antibiotic for the treatment of Clostridium difficile infection.•Synergistic results supported the likely use of curcumin as a supplement to current lines of drugs to enhance their activity. The rapid emergence of hypervirulent Clostridium difficile (C. difficile) isolates and the paucity of effective anti-clostridial antibiotics call for extensive research to identify new treatment options. This study aimed to test the anti-clostridial activity of bioactive extracts of turmeric, which is a natural herb widely known for its profound medicinal properties. The MICs of turmeric derivatives were determined against 27 C. difficile strains, including hypervirulent (BI/NAP1/027) and clinical toxigenic isolates. Additionally, their ability to inhibit C. difficile toxin production and spore formation was investigated. Furthermore, the safety profiles of turmeric derivatives regarding their effects on human gut microflora – such as Bacteroides, Lactobacillus and Bifidobacterium – were evaluated. Curcuminoids, the major phytoconstituents of turmeric – including curcumin, demethoxycurcumin and bisdemethoxycurcumin – inhibited growth of C. difficile at concentrations ranging from 4 to 32μg/mL. Additionally, curcuminoids showed no negative effect on major populating species of the human gut. Curcumin was more effective than fidaxomicin in inhibiting C. difficile toxin production, but less so in inhibiting spore formation. The findings suggest that curcumin has potential as an anti-clostridial agent. More work is needed to further investigate the efficacy of curcumin as a stand-alone drug or as a supplement of current drugs of choice, as it has no antagonistic activities but might overcome their drawbacks.