Blocking the alternative sigma factor RpoN reduces virulence of Pseudomonas aeruginosa isolated from cystic fibrosis patients and increases antibiotic sensitivity in a laboratory strain

Multidrug-resistant organisms (MDROs) are increasing in the health care setting, and there are few antimicrobial agents available to treat infections caused by these bacteria. Pseudomonas aeruginosa is an opportunistic pathogen in burn patients and individuals with cystic fibrosis (CF), and a leading cause of nosocomial infections. P. aeruginosa is inherently resistant to many antibiotics and can develop or acquire resistance to others, limiting options for treatment. P. aeruginosa has virulence factors that are regulated by sigma factors in response to the tissue microenvironment. The alternative sigma factor, RpoN (s 54 ), regulates many virulence genes and is linked to antibiotic resistance. Recently, we described a cis-acting peptide, RpoN*, which acts as a 9molecular roadblock9, binding RpoN consensus promoters at the -24 site and blocking transcription. RpoN* reduces virulence of P. aeruginosa laboratory strains both in vitro and in vivo , but its effects in clinical isolates was not known. We investigated the effects of RpoN* on phenotypically varied P. aeruginosa strains isolated from cystic fibrosis patients. RpoN* expression reduced motility, biofilm formation, and pathogenesis in a P. aeruginosa - C. elegans infection model. RpoN* expression increased susceptibility to several beta-lactam based antibiotics in the lab strain P. aeruginosa PA19660 Xen5 . Here, we show that using a cis-acting peptide to block RpoN consensus promoters has potential clinical implications in reducing virulence and enhancing the activity of antibiotics.