Study On The Pathogenic Mechanism Of Pseudomonas Aeruginosa

LOSS OF LASR FUNCTION ALTERS VIRULENCE FACTOR PRODUCTION IN CLINICAL ISOLATES OF PSEUDOMONAS AERUGINOSAObjective: To analyze clinical P.aeruginosa isolates with respect to their QS and virulence factor production.Methods: The fully functional Las R recombinants were constructed by allele exchange and complementary experiments.Secretion of autoinducer was detected by reporter strains.The expression of exotoxin A and Las B elastase were analyzed by western blot.Results Among ninety four isolates,one from blood and one from pleural effusion were identified to bear an identical Las R mutation,designated as Las RW60*.Comparing with the laboratory strain PAO1,the Las RW60* mutants were defective in biofilm formation,attenuated synthesis of autoinducer,3-oxo-C12HSL(3OC12HSL),and decreased production of elastase(Las B)and pyocynain.Surprisingly,the recombinant with fully functional Las R is required for the accumulation of 3OC12 HSL,Las B,and pyocyanin produced by P.aeruginosa cultures.Although Las R was not absolutely required for the generation of autoinducer,C4 HSL,it was generated more when las R is present than when it was absent.The mutants could not be complemented for biofilm formation by expressing las R.Conclusion: The altered virulence program upon the loss of Las R is likely to be important in the emergence of opportunistic P.aeruginosa infection.EFFECTS OF ANDROGRAPHOLIDE AND GENTAMICIN ON VIRULENCE FACTORS PRODUCED BY PSEUDOMONAS AERUGINOSA-STAPHYLOCOCCUS AUREUS MIXED BIOFILMObjective To study the effect of andrographolide and gentamicin on virulence factors production in mixed biofilm.Methods The model of burn mice infected by mixed biofilm was established,and the pathological tissues were detected under different intervention conditions.The secretion of signal molecules were detected in a mixed biofilm model in vitro.The activity of Las B elastase was detected by Congo red assay and pyocyanin was extracted by chemical method.q PCR was used to detect the expression of Exo S and Exo Y,and the expression of exotoxin A was detected by western blot.Results The results showed that the prognosis of tissue under the combined intervention was better than that of the single gentamicin group.In vivo signaling molecules in mixed biofilm found that Andro reduced the production of C4 HSL signaling molecules;virulence factor detection suggested that Andro reduced the production of pyocyanin in mixed biofilm but did not reduce the production of Las B elastase and Las A The The results of the q PCR suggested that Andro decreased the expression of Exo S and Exo Y;the result of western blot suggested that Andro reduced expression of Exo A.Conclusion Andro can reduce the tissue damage infected by mixed biofilm via reducing the production of some virulence factors.