The Effect Of Quorum Sensing Systems In Pseudomonas Aeruginosa Biofilms On The Expression Of AmpC Gene

Objective:To study the expression of AmpC gene in Pseudomonas aeruginosa induced by antibiotics at planktonic and biofilm phases.To study the effect of quorum sensing systems in Pseudomonas aeruginosa biofilms on the expression of AmpC gene induced by antibiotics.Methods:An in vitro model of Pseudomonas aeruginosa bacterial biofilms was established in silicon disk with modified fiat-board method.At the state of being induced by antibiotics,the expression of AmpC gene in PAO1,PAO1 with quorum sensing inhibitor(furanone C-30) and the mutants in quorum sensing systems was quantified by real-time quantitative PCR.Results:Without the effect of antibiotics,the expression of AmpC gene in PAO1 was low at both planktonic and biofilm phases.Being induced by imipenem and ceftazidime whose density can induced the maximal AmpCβ-lactamase activities,the expression of AmpC gene in biofilm PAO1 was higher than that in planktonic PAO1.At both planktonic and biofilm phases,the expression of AmpC gene in PAO1 induced by imipenem was higher than that induced by ceftazidime.With the effect of furanone C-30,the expression of AmpC gene in PAO1 induced by antibiotics at the planktonic phase and the biofilm phase was down-regulated.Futhermore the down-regulation at the expression of AmpC gene in biofilm PAO1 was larger than that in planktonic PAO1,the difference between the two phases of PAO1 was significant with statistic test method(P＜0.05).Being induced by antibiotics at both planktonic and biofilm phases,the expression ofAmpC gene in PAO-MWl and PAO-JP1 was lower than that in PAO1.CONCLUSION:Being induced by antibiotics,bilfilm PAO1 showed stronger ability for the expression of AmpC gene than planktonic PAO1.The expression of AmpC gene induced by imipenem was higher than that by ceffazidime.The quorum sensing systems in pseudomonas aeruginosa can regulate the expression of AmpC gene induced by antibiotics by direct Or indirect way.One possible reason of Pseudomonas aeruginosa bilfilm showing stronger ability forβ-lactamase production induced by antibiotics than planktonic bacteria is the different regulating effect of quorum sensing system at different phases.