Control of quorum sensing and virulence factors of Pseudomonas aeruginosa using phenylalanine arginyl β-naphthylamide

The spread of multidrug-resistant Pseudomonas aeruginosa isolates constitutes a serious clinical challenge. Bacterial efflux machinery is a crucial mechanism of resistance among P. aeruginosa. Efflux inhibitors such as phenylalanine arginyl beta-naphthylamide (PA beta N) promote the bacterial susceptibility to antimicrobial agents. The pathogenesis of P. aeruginosa is coordinated via quorum sensing (QS). This study aims to find out the impact of efflux pump inhibitor, PA beta N, on QS and virulence attributes in clinical isolates of P. aeruginosa. P. aeruginosa isolates were purified from urine and wound samples, and the antimicrobial susceptibility was carried out by disc diffusion method. The multidrug-resistant and the virulent isolates U16, U21, W19 and W23 were selected. PA beta N enhanced their susceptibility to most antimicrobial agents. PA beta N reduced QS signalling molecules N-3-oxo-dodecanoyl-L-homoserine lactone and N-butyryl-L-homoserine lactone without affecting bacterial viability. Moreover, PA beta N eliminated their virulence factors such as elastase, protease, pyocyanin and bacterial motility. At the transcription level, PA beta N significantly (P<0.01) diminished the relative expression of QS cascade (lasI, lasR, rhlI, rhlR, pqsA and pqsR) and QS regulated-type II secretory genes lasB (elastase) and toxA (exotoxin A) compared to the control untreated isolates U16 and U21. In addition, PA beta N eliminated the relative expression of pelA (exopolysaccharides) in U16 and U21 isolates. Hence, P. aeruginosa-tested isolates became hypo-virulent upon using PA beta N. PA beta N significantly blocked the QS circuit and inhibited the virulence factors expressed by clinical isolates of P. aeruginosa. PA beta N could be a prime substrate for development of QS inhibitors and prevention of P. aeruginosa pathogenicity.