Effects Of Andrographolide On The Production Of Virulence Factors Regulated By Quorum Sensing System And On The MRNA Expression Of MexAB-OprM Efflux Pump In Pseudomonas Aeruginosa

Objective Quorum sensing system plays an important role in the pathogenic agents and drug resistance of Pseudomonas aeruginosa. To evaluate the effect of andrographolide on virulence factors production in P. aeruginosa, and to make a primary investigation if andrographolide affect quorum sensing system.Method The wild type strain of P. aeruginosa PAO1 and QS double mutant strain PAO-JP2, which is uanble to produce autoinducers(AIs), were used in this study. This two strains were both included in andrographolide group and the control one. Growth rates of P. aeruginosa PAO1 in two groups were evaluated. Pyocyanin, proteolytic activity and elastase activity of these two strains were measured with or without the presence of andrographolide.Result The andrographolide did not affect the growth curve of PAO1 in planktonic culture. The production of pyocyanin in PAO1 was significantly suppressed in andrographolide group (P<0.05) but not in PAO-JP2. Proteolytic activity also showed remarkable discrease in PAO1 between andrographolide group and control(P<0.05), while this difference was not observed in cultures of PAO-JP2. Elastase activity were completely suppressed in PAO1 cultures grown in andrographolide group whereas no differences were showed in PAO-JP2 cultures.Conclusion The inhibiting effect of andrographolide on virulence factors production in P.aeruginosa may play a role in its anti-infection activity. Objective To develope a real-time PCR for determination mRNA expression of MexAB-OprM multidrug efflux pump and investigate the impact of andrographolide on MexAB-OprM mRNA expression in Pseudomonas aeruginosa.Method The fragments of mexB gene of mexAB-oprM operon and 30S rRNA gene rpsL were emplified and were cloned into plasmids. These plasmids were used as external standards for real-time PCR. Real-time PCR was applied to measure the mRNA expression of mexB and rpsL of Pseudomonas aeruginosa grown in medium with presence of different concentrations of andrographolide.Result The plasmids for standard curve were constructed. The relative mexB mRNA expression in the andrographolide groups were significantly lower than that in the control (P<0.05), while no significant difference was found within the andrographolide groups (P>0.05).Conclusion Andrographolide could reduce the mRNA expression level of mexAB-oprM, this effect might be one of the mechanisms that help to increase the sensitivity of Pseudomonas aeruginosa to antimicrobics.