Date of Submission

Fall 2020

Academic Program

Biology; Global Public Health

Project Advisor 1

Gabriel Perron

Abstract/Artist's Statement

Pseudomonas aeruginosa is a Gram-negative opportunistic pathogen that has been under intense scrutiny in recent years due to its rapidly evolving levels of antibiotic resistance and virulence. Although some strains of P. aeruginosa are harmless and can be found in virtually all soil and aquatic environments, other strains thrive in hospital environments and infect patients suffering from burn wounds and those with catheters or intubation. There are also clinical strains of P. aeruginosa specific to cystic fibrosis patients. P. aeruginosa uses a type III secretion system to inject effector proteins into host cells via a needle-like apparatus, but the specific exoenzymes it uses depends on the strain: although ExoT and ExoY are found in virtually every strain of P. aeruginosa, ExoS and ExoU are mutually exclusive. Nearly every existing strain of P. aeruginosa has one exoenzyme or the other, but on rare occasion a strain will be found that has both or neither. This study uses statistical methods in R to analyze genotype and phenotype data from a pre-existing library of P. aeruginosa strains with the goal of learning more about both exoS and exoU, and how selection for either exoenzyme contributes to the antibiotic resistance and virulence of a given isolate.

Results varied, but most were compatible with existing literature on the P. aeruginosa type III secretion system. While selection for either exoenzyme did not directly correlate with antibiotic resistance, ecological niche influenced isolates’ resistance to several antibiotics. A deeper dive into how exoenzyme selection and virulence differed between ecological niches revealed that although ExoS was consistently more common, ExoU was indicative for higher virulence in every niche except that of cystic fibrosis, where infections are chronic rather than acute.

Another result serving as an avenue for further research is increased selection for ExoU, the more fast-acting and virulent of the exoenzymes, over time. This indicates co-selection for ExoU alongside antibiotic resistance genes.

Open Access Agreement

On-Campus only

Creative Commons License

Creative Commons License
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