Pseudomonas aeruginosa

Abstract

Pseudomonas aeruginosa produces multiple virulence factors and causes different types of infections. Previous clinical studies identified P. aeruginosa isolates that lack individual virulence factors. However, the impact of losing several virulence factors simultaneously on the in vivo virulence of P. aeruginosa is not completely understood. The P. aeruginosa cell-to-cell communication system, or quorum sensing (QS), controls the production of several virulence factors.AnimalstudiesusingconstructedQSmutantsindicatedthatlossoftheQSsystemseverely impactsthevirulenceofP.aeruginosa.Inthisstudy,wetriedtodetermineifdeficiencywithintheQS system compromises the ability of P. aeruginosa to establish infections in humans. We have identified five QS-deficient strains through screening 200 isolates from patients with urinary tract, lower respiratory tract and wound infections. These strains lacked LasB and LasA activities and produced either no or very low levels of the autoinducers N-(3-oxododecanoyl) homoserine lactone and N-butyryl homoserine lactone. PCR analysis revealed that three isolates contained all four QS genes (lasI, lasR, rhlI and rhlR) while two isolates lacked both the lasR and rhlR genes. We also examined the five isolates for other virulence factors. The isolates produced variable levels of exotoxin A and, with one exception, were deficient in pyocyanin production. One isolate produced the type III secretion system (TTSS) effector proteins ExoS and ExoT, two isolates produced ExoT onlyandtwoisolatesproducednoTTSSproteins.Theisolatesproducedweaktomoderatebiofilms on abiotic surfaces. Analysis of the patients’ data revealed that two of the isolates represented a single strain that was isolated twice from the same patient within a 1 month interval. One QS