effect of azithromycin and phenylalanine-arginine beta-naphthylamide on quorum sensing and virulence factors in clinical isolates of pseudomonas aeruginosa

Background and objectives: pseudomonas aeruginosa is a problematic opportunistic pathogen causing several types of nosocomial infections with a high resistance rate to antibiotics. production of many virulence factors in p. aeruginosa is regulated by quorum sensing (qs), a cell-to-cell communication mechanism. in this study, we aimed to assess and compare the inhibitory effect of azithromycin (azm) and epi- paβn (efflux pump inhibitor- phenylalanine-arginine beta-naphthyl-amide) on qs system and qs-dependent virulence factors in p. aeruginosa clinical isolates. materials and methods: a total of 50 p. aeruginosa isolates were obtained from different types of clinical specimens. isolates were investigated for detection of qs system molecules by ahl cross-feeding bioassay and qs-dependent virulence factors; this was also confirmed by detection of qs genes (lasr, lasi, rhlr, and rhli) using pcr assay. the inhibitory effect of sub-mic azm and epi paβn on these virulence factors was assessed. results: all the p. aeruginosa, producing qs signals c hsl, failed to produce c hsl in the presence of sub-mic azm, 4 4 in the presence of epi paβn (20 µg/ml) only 14 isolates were affected, there was a significant reduction in qs-dependent virulence factors production (protease, biofilm, rhamnolipid and pyocyanin) in the presence of either 20 µg/ml epi or sub-mic of azm with the inhibitory effect of azm was more observed than paβn. conclusion: anti-qs agents like azm and epi (paβn) are useful therapeutic options for p. aeruginosa due to its inhibitory effect on qs-dependent virulence factors production without selective pressure on bacteria growth, so resistance to these agents is less likely to develop.