Pathogen virulence evolution increases pathogen growth in presence of antibiotics Open Access
Menezes, Arthur (Spring 2020)
Abstract
Serratia marcescens is a human opportunistic pathogen that is capable of rapidly evolving antibiotic resistance, posing a threat to public health. Increases in resistance are often associated with an increase in virulence or a better adaptation to stressful conditions due to the favored co- selection of resistance determinants and virulence modulating genes since they are both carried by mobile genetic elements. It is important to examine how S. marcescens evolution can impact its resistance to antibiotics. In order to test how virulence evolution impacts sensitivity to the antibiotic chloramphenicol, we used S. marcescens strains from White et al. (2020) that evolved increased virulence against C. elegans hosts and determined how antibiotic resistance changed compared to their ancestral strain. While we did not observe any changes to the minimum inhibitory concentration of antibiotic required to suppress bacterial growth, we found a statistically significant increase in S. marcescens growth in the presence of chloramphenicol when comparing S. marcescens evolved in the presence of hosts to S. marcescens evolved in the absence of hosts. Bacterial strains evolved in the presence of two different host genotypes displayed greater growth when compared to the control strains. Most notably, we saw that greater mean change in S. marcescens virulence was associated with a greater mean change in growth relative to the ancestor in the presence of chloramphenicol. As S. marcescens evolves in the presence of hosts, it becomes more resistant to antibiotics raising concerns as to whether antibiotics will be as effective in the future against evolved strains.
Table of Contents
Introduction...............................................................................................................................................1
Methods.....................................................................................................................................................6
Determining minimum inhibitory concentration (MIC) of chloramphenicol for ancestral and evolved
strains of Serratia marcescens.....................................................................................................................6
Measuring ancestral and evolved strains growth in
the presence and absence of chloramphenicol...........................................................................................8
Results.......................................................................................................................................................10
Ancestral And Evolved Strains Displayed Similar MIC..............................................................................10
Evolved Strains Exhibited Greater Growth Than Control Strains In Antibiotics.......................................12
Increased Virulence Is Associated With Increase In Growth In The Presence Of Antibiotics..................13
Discussion.................................................................................................................................................17 References.................................................................................................................................................20
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