The role of quorum sensing system in antimicrobial induced ampC expression in Pseudomonas aeruginosa biofilm

The aim of this study was to evaluate the effects of quorum sensing (QS) systems in Pseudomonas aeruginosa (P. aeruginosa) on the expression of ampC gene induced by antibiotics. An in vitro dynamic model of P. aeruginosa biofilms was established in a silicon tube in once-flowthrough system at 37 degrees C. Biofilm generation was identified by argentation. Biofilm morphology of standard P. aeruginosa strain (PAO-1) and QS systems deficient strains (PDO100, rhlI deficient strain; PAO-JP1, lasI deficient strain; and PAO-MW1, rhlI and lasI deficient strain) were observed by optical microscope. The expression of ampC in PAO1, PAO1 with QS inhibitor (furanone C-30) and the QS deficient strains before and after induced by antibiotics were quantified by real-time quantitative PCR. The biofilms of PAO-1 and PDO100 were much thicker and denser than that of PAO-JP1 and PAO-MW1. Being induced by antibiotics, the expression of ampC in PAO1 and PDO100 was significantly higher than that in PAO-MW1 and PAO-JP1. With the effect of furanone C-30, the expression of ampC in PAO1 induced by antibiotics was reduced in a dose-dependent manner. QS system, especially the las system, plays an important role in both biofilm formation and antimicrobials induced ampC expression and furanone C-30 is a potent inhibitor for P. aeruginosa QS system.