Synthetic dendrimeric peptide active against biofilm and persister cells of Pseudomonas aeruginosa

Antimicrobial dendrimeric peptides (AMDP) are a relatively new class of agents displaying repetitive functional groups on a branched core. Previously, we have investigated the length requirement for antimicrobial activity of peptides consisting of repeated arginine (R) and tryptophan (W) side chains and found that even short linear RW repeats are active, providing a starting point for a de novo design of multivalent structures. In this study, we synthesized and tested a new synthetic dendrimer, 2D-24, for its antimicrobial activity against Pseudomonas aeruginosa, including the wild-type PAO1 and its mucoid mutant PDO300. This synthetic AMDP was found to kill planktonic cells of both PAO1 and PDO300 in a dose-dependent manner, with nearly complete killing of both strains observed when treated with 50 μM of this agent. In addition to planktonic cells, 2D-24 was also found to kill biofilm cells of both strains in a dose-dependent manner. For example, treatment with 30 μM 2D-24 led to 94.4 ± 1.4 and 93.9 ± 4.2 % killing of PAO1 and PDO300 biofilm cells, respectively. Furthermore, 2D-24 was effective in killing multidrug-tolerant persister cells of PAO1 and PDO300. While higher concentrations of 2D-24 were required to kill persister cells, combinations of 2D-24 with ciprofloxacin, tobramycin, or carbenicillin showed synergistic effects on killing persister cells of both strains. Based on hemolysis assays using sheep erythrocytes and a coculture model of PAO1 and human epithelial cells, 2D-24 was found to kill P. aeruginosa cells at concentrations that are not toxic to mammalian cells.