Effect Of Imipenem On Expression Of AmpC Regulatory Proteins And OprD In Pseudomonas Aeruginosa Biofilms

Objective To study the gene expression of AmpC regulatory proteins AmpD, AmpE and AmpG and outer membrane protein OprD in Pseudomonas aeruginosa induced by imipenem at planktonic and biofilm phases, so as to explore the drug-resistance mechaniams of Pseudomonas aeruginosa.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 divided into four groups:planktonic, biofilms, planktonic exposed to 1/2MIC imipenem for 7 hours and biofilms exposed to 1/2MIC imipenem for 7 hours. The gene expression of AmpC regulatory proteins AmpD, AmpE and AmpG and outer membrane protein OprD were detected by Real-time fluorescent quantitative PCR.Results The gene expression level of AmpD, AmpE and AmpG were all low in both planktonic and biofilms in the absence of imipenem.There were no significant difference between the two groups(P>0.05). The gene expression level of AmpD, AmpE and AmpG of planktonic in the presence of imipenem were all higher than that of planktonic in the absence of imipenem. The former were 12.33,7.89 and 11.75 times as many as the later respectively. The difference had highly statistical significance between the two groups(P <0.01).The gene expression level of AmpD, AmpE and AmpG of biofilms in the presence of imipenem were all higher than that of biofilms in the absence of imipenem. The former were 30.73,31.79 and 11.25 times as many as the later respectively. The difference had highly statistical significance between the two groups(P<0.01).The gene expression level of AmpD and AmpE of biofilms in the presence of imipenem were all higher than that of planktonic in the presence of imipenem. The former were 2.47 and 4.08 times as many as the later respectively. The difference had statistical significance between the two groups(P<0.05). About gene expression level of AmpG, there was no significant difference between the two groups(P>0.05). About gene expression 1evel of OprD, there were no significant difference between planktonic and biofilms, planktonic in the presence and absence of imipenem, and biofilms in the presence and absence of imipenem(P>0.05).Conclusion The regulator genes of AmpC do not start up spontaneously in P. aeruginosa strain PAO1 as well as its synthetic gene. Imipenem can induce the expression level of AmpC regulator genes to increase. Biofilms are induced by imipenem to produce AmpD and AmpE more easily than planktonic. When exposed to imipenem, the gene expression level of outer membrane protein OprD of PAO1 does not decrease.