Quorum sensing is necessary for the virulence of Pseudomonas aeruginosa during urinary tract infection

Quorum sensing is a signaling pathway used by bacteria to monitor their population density by detecting small diffusible molecules. To understand the role of quorum sensing in pathogenesis of urinary tract infections, wild type Pseudomonas aeruginosa, having both functional las and rhl quorum sensing systems, and its isogenic single and double mutants were used in a mouse model of ascending urinary tract infection. Mice were evaluated on the basis of bacteriological and histopathological examinations, detection of acyl homoserine lactone, and the pathologic index factors of renal and bladder tissue. Single as well as double mutant strains were able to reach renal tissue, but they were not able to multiply and cause tissue damage. Reduced rates of infection, mild histopathologic lesions, and decreased production of pathologic index factors like myeloperoxidase, malondialdehyde, and reactive nitrogen intermediates were found in these groups of mice as compared to mice infected with a standard strain (PAO1) possessing both functional sensing systems. Loss of any one of the quorum-sensing components significantly reduced the in vivo virulence of P. aeruginosa in this mouse model of ascending urinary tract infection. Our results suggests that quorum-sensing signals may act as virulence factors and are essential for P. aeruginosa multiplication and virulence during the course of urinary tract infection. Kidney International (2009) 76, 286-292; doi:10.1038/ki.2009.183; published online 3 June 2009