Pharmacological Inhibition of the Pseudomonas aeruginosa MvfR Quorum-Sensing System Interferes with Biofilm Formation and Potentiates Antibiotic-Mediated Biofilm Disruption

Abstract

Pseudomonas aeruginosa biofilms contribute to its survival on biotic and abiotic surfaces and represent a major clinical threat due to their high tolerance to antibiotics. Therefore, the discovery of antibiofilm agents may hold great promise. We show that pharmacological inhibition of the P. aeruginosa quorum-sensing regulator MvfR (PqsR) using a benzamide-benzimidazole compound interferes with biofilm formation and potentiates biofilm sensitivity to antibiotics. Such a strategy could have great potential against P. aeruginosa persistence in diverse environments.KEYWORDS MvfR, PqsR, biofilm, antibiotic tolerance, antibiotic adjuvant, antibiotic potentiation, Pseudomonas aeruginosa, M64, antivirulence P seudomonas aeruginosa, a Gram-negative bacterium, is an opportunistic human pathogen commonly isolated from soil and water. This pathogen may be problematic due to its ability to form biofilms-multicellular aggregates embedded in selfproduced polymeric substances-that shield bacterial cells from antibacterial agents (such as disinfectants in water premise plumbing [1], host immune defenses [2,3]). It is well documented that biofilms greatly contribute to the establishment of chronic infections, including chronic pneumonia in cystic fibrosis patients, relapsing and chronic wound and ear infections, as well as medical device-related infections (3). Such infections are difficult to treat because biofilms are highly tolerant to antibiotics (2, 4, 5), calling for an urgent need to develop novel approaches to combat P. aeruginosa biofilms.One possible approach is the use of small molecules that interfere with the ability of P. aeruginosa to form biofilms. Several targets for antibiofilm drug development in P. aeruginosa have been proposed (3, 6), including the understudied MvfR quorumsensing (QS) system. This QS system is controlled by the transcriptional regulator MvfR (also known as PqsR) that regulates the pqsABCDE operon responsible for the synthesis of ϳ60 QS molecules called hydroxyl-2-alkyl-quinolines (HAQs) (7-10). The HAQ 3,4-hydroxy-2-heptyl-quinoline (PQS) as well as the enzymes PqsA and PqsD have been previously reported to play a role in biofilm formation, although their mechanism of action is not clear (11-13). We recently showed that another HAQ, 2-n-heptyl-4-hydroxyquinoline-N-oxide (HQNO), promotes biofilm formation and biofilm tolerance to antibiotics by inducing eDNA release that occurs as a result of autolysis due to self-poisoning of the respiratory chain by this molecule (14). A few studies have reported that inhibitors of PqsD or MvfR interfere with biofilm formation, but their antibiofilm potency was limited to the high micromolar range (11, 15-17). We recently described a benzamide-benzimidazole (BB) series of highly potent and cell-permeable

Targeting Antibiotic Tolerance, Pathogen by Pathogen

“…In the case of P. aeruginosa, candidates include bromo-furanones, patulin, penicillic acid, ajoene, mBTL, and benzamide-benzimidazole (Brackman and Coenye, 2015;O'Loughlin et al, 2013;Starkey et al, 2014). Inhibition of quorum sensing has been shown to induce a dispersion of P. aeruginosa biofilms (Hentzer et al, 2003) and increase sensitivity to aminoglycosides in in vivo P. aeruginosa experiments (Christensen et al, 2012;Maura and Rahme, 2017). However, current QSIs target downstream regulators as opposed to the central regulators of quorum sensing, which likely accounts for their mild to moderate efficacy (Manefield et al, 2002).…”

Effect of Capsicum Frutescens Extract, Capsaicin, and Luteolin on Quorum Sensing Regulated Phenotypes

“…In our assays P. aeruginosa PAO1 produced a more robust biofilm than S. marcescens MG1. Many studies show that P. aeruginosa PAO1 is a good biofilm producer (Lee & Zhang, ; Maura & Rahme, ; Rasamiravaka et al., ; Shrout, Tolker‐Nielsen, Givskov, & Parsek, ). In addition, Labbate et al.…”

“…In our assays P. aeruginosa PAO1 produced a more robust biofilm than S. marcescens MG1. Many studies show that P. aeruginosa PAO1 is a good biofilm producer (Lee & Zhang, 2015;Maura & Rahme, 2017;Rasamiravaka et al, 2015;Shrout, Tolker-Nielsen, Givskov, & Parsek, 2011). In addition, Labbate et al (2004) found that S. marcescens MG1 biofilm is formed solely by filamentous cells when grown for 24 hr, reaching maturity at 72 hr.…”

The State of the Union Is Strong: a Review of ASM's 6th Conference on Cell-Cell Communication in Bacteria

“…1). These compounds also perturb biofilm formation and can potentiate antibiotic-mediated biofilm disruption (48). Rahme went on to describe compounds that can inhibit PqsBC enzyme activity (i.e., the synthetic machinery responsible for the two MvfR-activating ligands HHQ and PQS [ Fig.…”