Quorum sensing and virulence factors among Pseudomonas aeruginosa isolates from various clinical sources

Pseudomonas aeruginosa is an opportunistic pathogen that causes serious human infections. The study of quorum sensing (QS) and its relation to various virulence factors among Pseudomonas clinical isolates could play an important role in eliminating its pathogenicity. C12HSL and C4-HSL are the key regulatory QS signals in P. aeruginosa. In the following study, QS signals and virulence factors; elastase, protease, pyocyanin, rhamnolipids, biofilm and ToxA were assessed among P. aeruginosa isolates obtained from different clinical sources (wounds, urine and sputum). Reporter strain assay of C12-HSL and C4-HSL revealed that 95% of the isolates produced C12-HSL and 89% possessed C4-HSL. PCR analysis of C12-HSL and C4HSL deficient isolates indicated the absence of synthase genes lasI and rhlI respectively. Deficiency of C12-HSL was prominent among sputum isolates however; C4-HSL deficient isolates were mainly from wound and urine samples. Furthermore, all isolates released elastase and 92% of the isolates produced protease in a significant correlation to signaling molecules C12-HSL and C4-HSL. Furthermore, 85% of the isolates released rhamnolipids in correlation to C4-HSL. All isolates formed biofilm and 94% produced pyocyanin but without significant correlation to either C12-HSL or C4-HSL. The relative expression of ToxA was performed among 10 tested isolates using RT-PCR. Some isolates showed very high level of ToxA reaching 20 fold of PAO1 with significant correlation to C12-HSL. In conclusion, P. aeruginosa from various sources possesses numerous virulence factors under the control of QS. Hence, QS is an important target for management of Pseudomonas infection.