Identification of echinacoside as a tobramycin potentiator againstPseudomonas aeruginosaaggregates

Abstract

AbstractCyclic diguanylate (c-di-GMP) is a central biofilm regulator, where increased intracellular levels promote biofilm formation and antibiotic tolerance. Targeting the c-di-GMP network is a promising anti-biofilm approach. Most agents reported previously decreased c-di-GMP to eliminate surface-attached biofilms, which did not recapitulatein vivobiofilms well and may thus impede their clinical impact. Here, the expression profile of genes encoding proteins associated with c-di-GMP metabolism was analysed among 32Pseudomonas aeruginosastrains grown as suspended aggregates in synthetic sputum or planktonic cells. A diguanylate cyclase, SiaD, proved essential for auto-aggregation underin vivo-like conditions. Virtual screening against SiaD identified echinacoside as an inhibitor, which reduced intracellular c-di-GMP levels and aggregate sizes and potentiated the efficacy of tobramycin against aggregates established by >80% of tested strains. This synergistic effect was also observed forin vivo-like 3-D alveolar cells infected by cytotoxicP. aeruginosa, demonstrating its high potential as an adjunctive therapy for recalcitrantP. aeruginosainfections.