OBJECTIVE To understand the effects of meropenem on the biofilms of Pseudomonas aeruginosa lasR/rhlR mutations in vitro.METHODS The biofilms of PAEO1 and its lasR,rhlR,and lasR rhlR mutants were incubated in a polyvinyl chloride tube in 0.9% saline for three days,then were immersed in meropenem solution of 26 ?g/ml for 24 hours,and examined by scanning electron microscopy(SEM).RESULTS After three days incubation,PAEO1 biofilms showed a well-developed structure,however,the biofilms of PAEO1 lasR,rhlR,and lasR rhlR mutants were thin and poor developed;after 24 hours in meropenem solution,PAEO1 biofilm become rareness,whereas PAEO1 lasR,rhlR,and lasR rhlR mutants biofilms were almost destructed and only small pieces left.CONCLUSIONS lasR/rhlR Genes play probably an important role in the formation of P.aeruginosa biofilm and in the resistance to meropenem.

OBJECTIVE To understand the effects of lasR/rhlR mutations on the biofilm formation of Pseudomonas aeruginosa in vitro.METHODS The biofilms of PAEO1 and lasR,rhlR,and lasR rhlR mutants were incubated in a polyvinyl chloride tube in 0.9% saline and studied by means of scanning electronic microscopy(SEM) after three days′ incubation.RESULTS After 3 day′s incubation,PAEO1 biofilm showed a well-developed structure,whereas thin and poor developed biofilms were seen in lasR/rhlR mutant groups.CONCLUSIONS lasR/rhlR Genes play probably an important role in the formation of P.aeruginosa biofilm in vitro.

OBJECTIVE To understand the importance of quorum sensing(QS)system in Pseudomonas aeruginosa(PAE)biofilm infection in lungs,the pathogenic effects of the wild-type P.aeruginosa PAEO1 were compared with QS double mutants PAEO1 lasR rhlR and PAEO1 lasⅠ rhⅡ in vivo.METHODS Rats were challenged intratracheally with alginate embedded PAE strain PAEO1 and the mutants of QS in the concentration of 1?109 colony-forming units per milliliter(CFU/ml).Two weeks post intratracheal challenge with P.aeruginosa,parameters were evaluated.RESULTS Two weeks after challenge,significantly milder microscopic and macroscopic lung pathology(P