Rhl quorum sensing affects the virulence potential of Pseudomonas aeruginosa in an experimental urinary tract infection.

Pseudomonas aeruginosa quorum sensing systems (QSS) las, rhl and PQS play a significant role in pathogenicity. Although multiple studies have explored the role of the las QSS in various types of infections, including urinary tract infections (UTIs), the role of the rhl QSS is still poorly understood. In this study, an attempt was made to explore the role of the rhl QSS in the pathogenesis of UTI. The wild-type strain P. aeruginosa PAO1 and its isogenic rhl QSS mutant strains, PDO-100 and PDO-111, were used. Strains were studied for the expression of extra-cellular virulence factors and the ability to induce experimental UTI in a mouse model. Evaluation was based on in vitro estimation of virulence factors (elastase, protease, rhamnolipid) and in vivo bacteriological and histopathological analysis of renal and bladder tissue. The cytokine levels were determined in the renal tissue of infected mice. Wild-type PAO1 showed the highest level of virulence traits. The tissue bacteriology and histopathology were indicative of establishment of UTI. The level of inflammatory cytokines was consistent with the bacteriology and pathology results. The rhl QSS mutant strains showed significantly reduced pathogenicity. On supplementation with C4-homoserine lactone, strain PDO-100 showed a significant increase in pathogenicity. The results indicate that the rhl QSS affects the virulence potential of P. aeruginosa and that, despite the presence of the las QSS, mutant strains exhibited reduced pathology. Therefore, the rhl QSS may be exploited in more detail for future drug intervention tactics.