From in vitro to in vivo : establishment of a test system for the biological evaluation of novel quorum sensing inhibitors as anti-infectives against Pseudomonas aeruginosa

摘要

Innovative, efficient anti-infectives are needed because of increasing antibiotic resistance. Thus, strategies have been proposed interfering with bacterial pathogenicity instead of viability such as inhibition of quorum sensing. This intercellular communication system uses signal molecules to coordinate virulence and biofilm formation. Pseudomonas aeruginosa uses unique signal molecules such as 2-heptyl-3-hydroxy-4-(1H)-quinolone (PQS). Therefore, compounds should be developed blocking their biosynthesis and reception by inhibiting PqsD and antagonizing PqsR, respectively. In this thesis, novel PqsD inhibitors were studied. The best compound strongly inhibited the production of signal molecules and biofilm without affecting growth. Irreproducibility of routine quantification of PQS in P. aeruginosa cultures was overcome by development and validation of a novel LC-MS/MS approach. A functional inversion was identified as reason for ineffectiveness of the first PqsR antagonist in P. aeruginosa. Blocking the metabolic hot spot led to a very potent anti-infective fully protecting Galleria mellonella larvae from lethal P. aeruginosa infection. This was the first proof-of-concept for an anti-infective therapy targeting PqsR. Optimization of the physicochemical properties of the respective compound class resulted in a new compound with improved water solubility and efficient reduction of signal molecules and virulence factor formation.