Doctor of Philosophy in Biology

In the

School of Biological Sciences

Jelly Vanderwoude

Will defend her dissertation

EVOLUTION, VIRULENCE, AND RESISTANCE IN CHRONIC PSEUDOMONAS AERUGINOSA INFECTION

30th of August, 2023

1:00 PM

Price Gilbert 4222

https://gatech.zoom.us/j/7049491206

 Thesis Advisors:

Stephen P. Diggle, Ph.D.

School of Biological Sciences

Georgia Institute of Technology

Sheyda Azimi, Ph.D.

Department of Biology

Georgia State University

Committee Members: 

Sam P. Brown, Ph.D.

School of Biological Sciences

Georgia Institute of Technology

Marvin Whiteley, Ph.D.

School of Biological Sciences

Georgia Institute of Technology

Timothy D. Read, Ph.D.

Division of Infectious Diseases

Department of Medicine

Emory University

Joanna B. Goldberg, Ph.D.

Division of Pulmonology, Asthma, Cystic Fibrosis, and Sleep

Department of Pediatrics

Emory University

ABSTRACT: Pseudomonas aeruginosa is a versatile opportunistic pathogen known to cause a spectrum of human disease, including chronic wound and cystic fibrosis (CF) lung infections. Due to its intrinsic resistance to antibiotics, arsenal of virulence factors, and immune-evading adaptations, chronic P. aeruginosa infection is challenging to treat. Population heterogeneity may be a contributing factor to treatment failure, as diverse microbial populations harbor more resistance mechanisms and rare variants that evade detection. The rapid rise in antimicrobial resistance (AMR) rates in clinical P. aeruginosa strains has intensified the challenges associated with treating these infections, necessitating improved understanding of how these dynamic populations evolve and novel approaches beyond conventional antibiotics, such as anti-virulence drugs.

This thesis explores the evolution of virulence and AMR in order to illuminate the evolutionary landscape of chronic P. aeruginosa infection. The first study delves into P. aeruginosa virulence evolution and evolutionary adaptations in an understudied system, chronic wounds. In a two-part serial passage and sepsis experiment in murine chronic wounds, virulence evolved divergently in each of three lines of evolution. Morphological diversity of these evolved populations was constrained, highlighting potential differences between chronic wound and CF lung environments. Virulence genes commonly mutated in CF lung infection were also mutated in these evolved populations, with evidence of parallel evolution, revealing shared genetic adaptations across diverse infection settings.

The second study explores the relationship between genomic diversification and AMR diversity in P. aeruginosa populations extracted from individuals with CF to understand the molecular and evolutionary basis of AMR diversity. Genomic diversity was neither a reliable predictor of nor a requisite for phenotypic AMR diversity, as populations with widely varying genetic backgrounds and levels of genomic diversity exhibited comparable levels of AMR diversity. Hypermutator strains in these populations often displayed increased sensitivity to antimicrobials, even in cases where strains had been subject to treatment by the same antibiotic within the patient. There was poor evidence for either collateral sensitivity or trade-offs between AMR and fitness in these populations, suggesting AMR diversity may be driven by other evolutionary forces.

Taken together, these findings elucidate the evolutionary pathways exploited by P. aeruginosa during chronic infection, highlighting key similarities and differences across two important infection systems.