The dispirotripiperazine compound PDSTP impairs Pseudomonas aeruginosa and Burkholderia cenocepacia adhesion to lung epithelial cells through a novel mechanism of action

Pseudomonas aeruginosa and Burkholderia cenocepacia remain critical pathogens in cystic fibrosis (CF) involved in lung decline due to their high intrinsic antibiotic resistance. To address the shortage of effective therapeutics, preventing bacterial adhesion represents a promising alternative strategy to avoid the establishment of chronic infections. The dispirotriperazine compound PDSTP significantly blocked the adhesion of B. cenocepacia J2315 to human epithelial cells but was ineffective against K56-2 isolate. We demonstrated that the O-antigen in K56-2 mediates resistance to PDSTP. Pre-incubation assays confirmed that PDSTP interacts directly with both human and bacterial cells to exert its effect. In bacteria, this interaction is driven by electrostatic forces between the cationic spiro centers of PDSTP and the anionic moieties of the outer membrane lipopolysaccharide (LPS), as confirmed by competition and dansyl polymyxin B displacement assays. Notably, PDSTP displayed a higher binding ability for the P. aeruginosa PAO1 surface LPS than for that of B. cenocepacia . Furthermore, host cell surface heparan sulfate (HS) chains played distinct roles: while HS deficiency did not impair PDSTP efficacy against P. aeruginosa , heparinase treatment markedly decreased PDSTP activity against B. cenocepacia J2315. This identified host HS as a crucial mediator for both B. cenocepacia adhesion and PDSTP anti-adhesive effect. These findings demonstrate that, while PDSTP employs a core mechanism of action centered on electrostatic interactions with bacterial surface LPS, its anti-adhesive efficacy and dependence on host HS are highly modulated by species-specific surface structures. This study highlights the potential of PDSTP as a versatile preventive agent against multidrug-resistant CF pathogens.