Investigating the Role of the Las and Rhl Quorum Sensing Systems in the Pathogenesis of Pseudomonas aeruginosa

Pseudomonas aeruginosa is an opportunistic bacterial pathogen commonly associated with increased morbidity and mortality in cystic fibrosis (CF) patients. To adapt to the CF lung environment, P. aeruginosa undergoes multiple genetic changes as it moves from an acute to a chronic infection. The resultant phenotypes have been associated with chronic infection and can provide important information to track the patient’s individualized disease progression. This study examines the link between the accumulation of QS genetic mutations and phenotypic expression in P. aeruginosa laboratory strains and clinical isolates. We utilized several plate-based and colorimetric assays to quantify the production of pyocyanin, rhamnolipids, and protease from paired clinical early- and late-stage chronic infection isolates across 16 patients. Exoproduct production of each isolate was compared to the mean production of pooled isolates to classify high producing (QS-sufficient) and low producing (QS-deficient) isolates. We found that over time P. aeruginosa isolates exhibit a reduction in QS-related phenotypes during chronic infections. Future research of the QS regulatory networks will identify whether reversion of genotype will result in corresponding phenotypic changes in QS-deficient chronic infection isolates.