Phenotypic Heterogeneity And Mechanism Of Pseudomonas Aeruginosa In Chronic Lung Infection And Chronic Wound Infection

Objective: In this study,we compared the phenotypic heterogeneity of Pseudomonas aeruginosa isolated from the lung and wound infections in chronic infections and conducted a preliminary investigation of the related mechanisms.This research can provide experimental basis for clinical treatment of infection caused by Pseudomonas aeruginosa.Methods: 1.Phenotypes of Pseudomonas aeruginosa collected from chronic wound infection and chronic lung infection were determined: ⑴ Twitching motility and swimming motility were measured using Luria-Bertani agar medium and Casein Tryptone medium.⑵ Azo casein and skim milk plate assay to detect the secretion of protease.⑶ PDP medium was used to detect the secretion of pyocyanin.⑷Pseudomonas aeruginosa was cultured for 48 hours to determine the production of Pyomelanin,Pyoverdine and Mucoidy by bacterial color and state.⑸ The crystal violet and congo red method were used to detect biofilm formation ability.2.Genomic DNA of Pseudomonas aeruginosa was extracted.Identification of virulence genes were performed using polymerase chain reaction(PCR).3.Using Pseudomonas aeruginosa genomic DNA as a template,muc A,a key gene controlling alginate production,was amplified and sequenced,and mutations in muc A were analyzed.4.Multi-locus sequence typing(MLST)were performed using polymerase chain reaction(PCR).Results: 1.A total of 38 strains from lung infection and 21 strains from wound infection were collected.2.No significant difference was found in the distribution of Twitching、Swimming,Biofilm,Pyocyanin,Protease,Pyomelanin and Pyoverdine.However,there was a significant difference in the distribution of Mucoidy(P<0.05).3.No significant difference was found in the distribution of virulence genes exo S,las B,tox A.Significant difference was found in the distribution of exo U(P<0.05).4.All 38 Pseudomonas aeruginosa strain from lung infections occurred muc A gene mutation.A total of 6mutations were detected in lung infections strains: A→G,C→T,T→C,T→G,G→A,C→A.21 strains of wound origin were mutated with 100% mutation rate Nine mutations were detected in the wound infections: T→C,C→T,G→A,A→G,C→A,C→G,T→G,G→C,A→T.5.ST244 is the most popular clonotypes.Conclusion: Pseudomonas aeruginosa has phenotypic heterogeneity in chronic infection at different sites: Pseudomonas aeruginosa of chronic lung infection showed more mucoid phenotype and higher alginate content than Pseudomonas aeruginosa form chronic wound infection.The relevant mechanisms involved in this difference need to be explored.The adaptability of Pseudomonas aeruginosa in the environment of chronic lung infection makes Pseudomonas aeruginosa do not cause a sharp inflammatory response of the host,and it also facilitates the escape of Pseudomonas aeruginosa from host clearance and thus its long-term coexistence with the host.