Phenotypic and Genotypic Evaluation of the Prairie Epidemic Strain (PES): A Transmissible Strain of Pseudomonas aeruginosa Found in Patients With Cystic Fibrosis
Abstract
Epidemic strains of Pseudomonas aeruginosa have been found worldwide in cystic fibrosis (CF) patients. The recently described Prairie Epidemic Strain (PES) is found in patients attending several Western Canadian CF clinics. In this study, we characterized PES genotypically and phenotypically.
The clonality of PES was first described using pulse-field gel electrophoresis. Here we confirm that observation with multi-locus sequence typing, where PES isolates from unrelated patients were identified to have ST192 consistently.
As epidemic strains are associated with worse clinical outcomes, we assessed the pathogenic potential of PES relative to other epidemic strains (OES) and local non-epidemic isolates. We conducted a comparative analysis using fourteen phenotypic traits, including virulence factor production, biofilm formation, planktonic growth, mucoidy, and antibiotic susceptibility to characterize 118 P. aeruginosa isolates. The analysis indicated that the OES and local non-epidemic isolates had distinct phenotypic traits, but PES shared characteristics with both of the other groups.
Strain replacement was identified amongst five patients whereby local non-epidemic isolates were displaced by PES. These PES isolates produced lower levels of proteases and elastases but were more resistant to antibiotics compared to the displaced non-epidemic isolates suggesting that virulence is not the sole factor involved in displacing previous colonizers. Simulations of super-infections using the Drosophila melanogaster model demonstrated that a PES isolate was able to attenuate virulence when co-infected with a local non-epidemic isolate, which suggested that bacterial competition was occurring with PES having a competitive advantage. This study aimed to elucidate potential mechanisms used in strain replacement and investigated the role of the type 6 secretion system (T6SS) by using a cell-dependent killing assay. These assays indicated that the T6SS is not likely the mechanism that the PES were using to outcompete the local non-epidemic isolates.
This comparative analysis is the first to be done on a large scale between groups of epidemic and non-epidemic CF P. aeruginosa isolates. This work is significant because it aimed to better understand epidemic P. aeruginosa infections in the CF population.
Description
Keywords
Microbiology
Citation
Duong, J. (2017). Phenotypic and Genotypic Evaluation of the Prairie Epidemic Strain (PES): A Transmissible Strain of Pseudomonas aeruginosa Found in Patients With Cystic Fibrosis (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/27332