Antimicrobial resistance (AMR) has emerged as a major global challenge for livestock production [1]. AMR not only exacerbates bacterial infections across various livestock species and complicates disease management, but also reduces treatment efficacy and increases animal mortality. Furthermore, the spread of resistance undermines overall production efficiency, raises operational costs, and poses potential threats to food safety and public health [2,3]. The emergence of multidrug-resistant bacteria, such as methicillin-resistant Staphylococcus aureus (MRSA) [4,5], vancomycin-resistant Enterococcus (VRE) [6,7], and carbapenem-resistant Pseudomonas aeruginosa (CRPAE) [8], has exacerbated antibiotic resistance. The lack of effective new antibiotics against resistant bacteria represents a growing global public health concern [9]. New agents displaying innovative chemistry and modes of action are urgently needed to tackle the public health threat posed by antimicrobial resistance [10].

Enterococcus are ubiquitous commensals in the gastrointestinal tract of food-producing animals, yet specific lineages can act as opportunistic or primary pathogens in intensive production systems [11]. In poultry, enterococcal disease (notably associated with E. faecalis and E. cecorum) has been increasingly recognized as a major health and welfare problem, presenting as systemic infection and musculoskeletal disorders (e.g., spondylitis/osteomyelitis and lameness), which translate into reduced growth, poorer flock performance, increased mortality, and meaningful economic losses [12]. Vancomycin serves as the last line of defense in the clinical treatment of multidrug-resistant (MDR) bacterial infections [13]. The emergence of VRE has significantly diminished the efficacy of vancomycin treatment [14]. Currently, antibiotics used in clinical treatment of VRE include linezolid, daptomycin, tigecycline, and others [15]. However, neither tigecycline nor linezolid has a bactericidal effect, and daptomycin is only active at high doses and its use is restricted [16]. Therapeutic options are very limited against VRE infections, and there is an urgent need to develop antimicrobial agents to target resistant bacterial infections.

As an effective antibacterial therapy, small molecule antibacterial materials have shown unprecedented advantages. Kerolos et al. discovered a novel class of antibiotics produced by a simple one-pot reaction of indole and phthalaldehyde against Enterococcal strains [17]. Marius et al. synthesized two new thiophenocarbazole needles with new antibacterial agents for Staphylococcus and Enterococcus and had excellent antibacterial effects in vitro [18]. In recent years, a series of cationic or amphiphilic AIEgens have been designed to interact with negatively charged bacterial membranes, enabling efficient bacterial labeling and killing in the aggregated state [[19], [20], [21]]. Many AIEgens have been engineered as photosensitizers for photodynamic antibacterial therapy, where light-triggered generation of reactive oxygen species (ROS) leads to rapid membrane damage and cell death [22]. Other AIE-active molecules have been reported to exert dark toxicity through membrane disruption, intracellular energy depletion, or interference with redox homeostasis [23]. Despite these advances, studies specifically targeting VRE remain relatively limited, particularly in the context of livestock-associated infections. In addition, systematic investigations of the underlying mechanisms of action and in vivo validation in relevant animal models are still lacking. Therefore, there is an urgent need to develop and characterize AIE-active molecules with potent activity against VRE and to elucidate their antibacterial mechanisms under physiologically relevant conditions.

In this work, we integrated in vitro antibacterial assays, untargeted metabolomics, and a mouse intestinal colonization model with histopathological evaluation to assess the antibacterial activity of the 4-(7-(4-(diphenylamino) phenyl) benzo[c] [1,2,5] thiadiazol-4-yl)-N, N, N-trimethylbenzenaminium (TBP-TA) against VRE and to elucidate its bactericidal mechanism. Our results indicate that TBP-TA is a promising candidate for the treatment of VRE-associated infections.