Effects of afabicin desphosphono (Debio 1452) on gut microbiota and subsequent risk of simulated Clostridium difficile infection in an in vitro human gut model

Background: Afabicin is a novel inhibitor of bacterial fatty-acid synthesis currently in clinical development for the treatment of staphylococcal bone and joint infections and acute bacterial skin and skin structure infections.This narrow-spectrum agent has been shown to spare murine and human gut microbiota.Afabicin (Debio 1450) is administered as a prodrug that is converted to the active moiety, Debio 1452.Objectives: A validated in-vitro human gut model was used to assess the impact of two Debio 1452 dosing regimens on gut microbiota composition, antimicrobial resistance (AMR) gene abundance, and risk of simulated Clostridioides difficile infection (CDI).Methods: Four gut models were inoculated with pooled human faeces and challenged with 10 7 cfu C. difficile spores.Models were then exposed to either low-dose Debio 1452 (17.8 mg/L twice daily), high-dose Debio 1452 (35.7 mg/L twice daily), levofloxacin (140.55 mg/L once daily), or a dimethyl sulfoxide control, each for 14 days, followed by a 4-week observation period.C. difficile populations, cytotoxin levels, and microbiota profiles (culture and sequencing) were monitored throughout.Results: Neither Debio 1452 regimen caused substantial disruption to gut microbiota or triggered simulated CDI, closely resembling the non-antimicrobial control.In contrast, levofloxacin induced marked microbiota perturbation, followed by C. difficile germination, proliferation, and toxin production.Levofloxacin exposure also increased the abundance of several AMR gene classes, including macrolide, tetracycline, and beta-lactam resistance determinants-an effect not observed with Debio 1452. Conclusions:These findings indicate that Debio 1452 exerts minimal impact on the gut microbiota and may carry a lower risk of CDI compared with broad-spectrum antibiotics.