Repurposing Antibacterial Drugs and Clinical Molecules to Combat Vancomycin-Resistant Enterococci (VRE)

Vancomycin-resistant enterococci (VRE) is a growing threat to public health due to its increasing prevalence and limited treatment options. The urgent need for alternative therapeutics necessitates novel strategies such as drug repurposing to identify effective antimicrobial agents. In this study, we screened a library of 1,135 antibacterial compounds to identify candidates with activity against VRE. A total of 58 active compounds were identified, with ridinilazole and CRS3123 emerging as the most promising hits. Both compounds exhibited potent antibacterial activity in the nanomolar range against multiple Enterococcus species, including vancomycin-resistant and vancomycin-sensitive E. faecium, E. faecalis, E. hirae and E. durans . CRS3123 demonstrated exceptional potency, exhibiting MIC values of <0.007 μg/mL against most strains. Ridinilazole exhibited an MIC spectrum of <0.007 to 1 μg/mL across all strains, with E. faecium being the most sensitive (MIC: <0.007–0.25 μg/mL) and E. faecalis displaying a higher MIC range (0.5–1 μg/mL). Time-kill assays indicated that both compounds exhibited bacteriostatic activity comparable to linezolid. Additionally, ridinilazole and CRS3123 displayed low cytotoxicity in Vero cells and no hemolytic activity, suggesting a favorable safety profile. In vivo studies using the C. elegans infection model further confirmed their efficacy, with ridinilazole achieving a 60% reduction in VRE burden, CRS3123 resulting in a 25% reduction, and linezolid demonstrating a 55% reduction. These findings highlight ridinilazole and CRS3123 as promising candidates for further development for managing VRE infections.