Study On The Expression Of MexAB-OprM And MexR In Pseudomonas Aeruginosa Biofilms

Objective To study the expression of MexAB-OprM and its repressor protein-MexR in planktonic and biofilm bacteria of Pseudomonas aeruginosa when exposed to imipenem and ciprofloxacin.Methods The P.aeruginosa strain PAO1 was used in this study.In vitro models of Pseudomonas aeruginosa bacterial biofilm were built up in eppendorf tube and a rapid staining procedure of crystal violet was used to verify them.The test was developed under two groups,planktonic and biofilm bacteria of Pseudomonas aeruginosa.The planktonic were exposed to 1/2MIC imipenem and ciprofloxacin for 4 hours;The biofilms were exposed to 4 MIC imipenem and 2 MIC ciprofloxacin for 12 hours,the expression of multiple drugs efflux pumps MexAB-OprM and its repressor protein MexR were detected by using the method of Real-time quantitative PCR at the days of 3 and 5 after biofilms forming.Results When the P.aeruginosa strain PAO1 transferred its growth mode from planktonic to biofilms(days of 3 and 5),the efflux pump MexAB-OprM gene expression level was significantly decreased(P<0.05),the highest relative quantity level was nearly 10 folds decreased compared to the lowest.The difference was significant between planktonic and biofilms.As the biofilms on the days of 3 and 5,though the relative quantity was 3 folds lower,but it was not different.The expression level of repressor protein MexR had no difference between planktonic and bioiflms(days of 3 and 5)(P>0.05).The expression of MexAB-OprM and MexR of biofilms on the days of 3 and 5 had no statistical significance(P>0.05).The expression level of MexAB-OprM and MexR,none was different after imipenem and ciprofloxacin induced both in planktonic and biofilms.Conclusion When pseudomonas aeruginosa PAO1 transferred its growth mode from planktonic to biofilms,the expression level of efflux pumps MexAB-OprM was greatly decreased,the MexR had no change.There had no difference of MexAB-OprM and MexR between 3days and 5days after biofilm forming.Imipenem and ciprofloxacin had no effect on the expression of MexAB-OprM and MexR both in planktonic and biofilms.