Metronidazole-ursodeoxycholic acid bifunctional antibacterial: A promising strategy to combat Clostridium difficile infection and prevent recurrence

Current treatments against Clostridium difficile infection (CDI), such as vancomycin and metronidazole, frequently lead to severe recurrence due to disruption of gut microbiota balance, which results in a pressing need for new chemical entities to treat CDI. Bile acids, such as UDCA, have been demonstrated to inhibit the growth and spore germination of C. difficile, and regulate the structure of the intestinal flora. This study involved the synthesis of eight bile acid-metronidazole hybrids. Among them, the most promising hybrid, SCUT1-2, effectively killed the vegetative cells of C. difficile with a minimum inhibitory concentration (MIC) of 0.06–0.50 μg/mL, and inhibited spore germination in vitro. The absolute bioavailability of SCUT1-2 (F = 56.8 %) indicated that approximately half of SCUT1-2 was absorbed systemically, while a considerable portion remained in the gastrointestinal tract in its original form, laying a solid foundation for its effective action in vivo. SCUT1-2 could effectively alleviate the symptoms of weight loss and diarrhea in mice caused by CDI and effectively reduce the relevant expressions of inflammatory factors, outperforming metronidazole. Furthermore, SCUT1-2 demonstrated a favorable therapeutic effect in reducing mortality and disease symptoms in CDI mice by killing C. difficile cells and regulating the composition and structure of the intestinal flora. Notably, SCUT1-2 could effectively prevent recurrent CDI. This work provides a potential clinical lead for the development of CDI therapies and highlights hybrid medication as a new strategy.