Peptide dendrimers G3KL and TNS18 inhibit Pseudomonas aeruginosa biofilms

Herein we report that peptide dendrimers G3KL and TNS18, which were recently reported to control multidrug-resistant bacteria such as Staphylococcus aureus, Pseudomonas aeruginosa, and Acinetobacter baumannii, strongly inhibit biofilm formation by P. aeruginosa PA14 below their minimum inhibitory concentration (MIC) value, under which conditions they also strongly affect swarming motility. Eradication of preformed biofilms, however, required concentrations above the MIC values. Scanning electron microscopy observation and confocal laser scanning micrographs showed that peptide dendrimers can destroy the biofilm morphological structure and thickness in a dose-dependent manner, even make the biofilm dispersed completely. Membrane potential analysis indicated that planktonic cells treated with peptide dendrimers presented an increase in fluorescence intensity, suggesting that cytoplasmic membrane could be the target of G3KL and TNS18 similarly to polymyxin B. RNA-seq analysis showed that the expressions of genes in the arnBCADTEF operon-regulating lipid A modification resulting in resistance to AMPs are differentially affected between these three compounds, suggesting that each compound targets the cell membrane but in different manner. Potent activity on planktonic cells and biofilms of P. aeruginosa suggests that peptide dendrimers G3KL and TNS18 are promising candidates of clinical development for treating infections.