Dual-Functional Antibiotic Adjuvant Displays Potency against Complicated Gram-Negative Bacterial Infections and Exhibits Immunomodulatory Properties.

The treatment of Gram-negative bacterial infections is challenged by antibiotic resistance and complicated forms of infection like persistence, multispecies biofilms, intracellular infection, as well as infection-associated hyperinflammation and sepsis. To overcome these challenges, a dual-functional antibiotic adjuvant has been developed as a novel strategy to target complicated forms of bacterial infection and exhibit immunomodulatory properties. The lead adjuvant, D-LBDiphe showed multimodal mechanisms of action like weak outer membrane permeabilization, weak membrane depolarization, and inhibition of efflux machinery, guided primarily by hydrogen bonding and electrostatic interactions, along with weak van der Waals forces. D-LBDiphe potentiated antibiotics up to ∼4100-fold, targeted phenotypic forms of antibiotic tolerance, and revitalized antibiotics against topical and systemic infections of in mice. The aromatic moiety in D-LBDiphe was instrumental for interaction with lipopolysaccharide (LPS) micelles, and this interaction was the driving factor in reducing pro-inflammatory cytokines by 61.8-79% in mice challenged with LPS. Such multifarious properties of a weak-membrane perturbing, nonactive and nontoxic adjuvant have been discussed for the first time, supported by detailed mechanistic understanding and elucidation of structure-guided properties. This work expands the scope of antibiotic adjuvants and validates them as a promising approach for treatment of complicated bacterial infections and inflammation.