Exploring the Evolutionary Relationship Between Virulence and Drug Resistance
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Authors
van den Hoogen, Josée
Date
Type
thesis
Language
eng
Keyword
Mathematical Biology , Virulence , Drug Resistance , Plasmid , Superinfection , Reproductive Ratio
Alternative Title
Abstract
One of the many possible negative outcomes of pathogen evolution is the emergence of a virulent drug resistant strain. A pathogen may exploit plasmid-mediated gene transfer to gain drug resistance and virulence genes in an attempt to become the exclusive infection. To answer questions on the possible emergence of a virulent drug resistant strain we constructed a nine dimensional SIS model with treatment. We used plasmid-mediated gene transfer by way of superinfection to distribute virulence and drug resistance genes. By examining the resulting system of differential equations at the two extremes of treatment level (%0 and %100), we determined the stability of the single strain endemic infection equilibrium points of interest. In the absence of treatment we determined a set of ancestral conditions which provided constraints on the model parameters. In the presence of treatment we focused on the ability of the
virulent drug resistant (AB) strain to invade the avirulent drug resistant (B) strain. We were able to express these invasion conditions in terms of novel reproductive ratios that incorporated both non-superinfection effects and superinfection effects.
Our model reveals that plasmid-mediated gene transfer by way of superinfection increases the parameter space allowing for virulence to evolve in a drug resistant population. However, virulence in a drug resistant population is not always more
likely to evolve in comparison to virulence in a drug sensitive population.
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Queen's University's Thesis/Dissertation Non-Exclusive License for Deposit to QSpace and Library and Archives Canada
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Copying and Preserving Your Thesis
This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner.
ProQuest PhD and Master's Theses International Dissemination Agreement
Intellectual Property Guidelines at Queen's University
Copying and Preserving Your Thesis
This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner.