Dictyostelium discoideum as a surrogate host–microbe model for antivirulence screening in Pseudomonas aeruginosa PAO1

• Using a virtual screening approach, compounds that inhibit Pseudomonas aeruginosa PAO1 polyphosphate kinase 1 (PaPPK1) in vitro were identified.
• A simple high-throughput developmental assay using Dictyostelium discoideum for discovering novel antivirulence agents against P. aeruginosa PAO1 without side effects to the host or its beneficial bacteria was designed.
• PPK1 inhibitors showed in vivo antivirulence activity toward P. aeruginosa PAO1.

The interest of the pharmaceutical industry in developing new antibiotics is decreasing, as established screening systems which identify compounds that kill or inhibit the growth of bacteria can no longer be used. Consequently, antimicrobial screening using classical minimum inhibitory concentration (MIC) measurements is becoming obsolete. The discovery of antimicrobial agents that specifically target a bacterial pathogen without affecting the host and its beneficial bacteria is a promising strategy. However, few host–microbe models are available for in vivo screening of novel antivirulence molecules. Here we designed high-throughput developmental assays in the social amoeba Dictyostelium discoideum to measure Pseudomonas aeruginosa virulence and to screen for novel antivirulence molecules without side effects to the host and its beneficial bacteria Klebsiella aerogenes. Thirty compounds were evaluated that had been previously selected by virtual screening for inhibitors of P. aeruginosa PAO1 polyphosphate kinase 1 (PaPPK1) and diverse compounds with combined PPK1 inhibitory and antivirulence activities were identified. This approach demonstrates that D. discoideum is a suitable surrogate host for preliminary high-throughput screening of antivirulence agents and that PPK1 is a suitable target for developing novel antivirulence compounds that can be further validated in mammalian models.