Application of nanomotion to investigate antibiotics tolerance in Escherichia coli and viability of Chlamydiales bacteria


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PhD thesis: a PhD thesis.
Application of nanomotion to investigate antibiotics tolerance in Escherichia coli and viability of Chlamydiales bacteria
AUBRY Christèle
Greub Gilbert
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Université de Lausanne, Faculté de biologie et médecine
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Antibiotic treatment failure is a global health issue, leading to more than one million deaths each year and having an effect on close to five million others1. lt is often caused by resistant bacteria, which have inherited the ability to grow at high antibiotic concentrations, independently of the duration of treatment. lt has been projected that by the year 2050, approximately ten million deaths each year will be attributed to microbial resistance2• Furthermore, certain bacterial strains have developed a degree of tolerance towards antibiotics, enabling them to subsist through episodic contact with concentrations of these drugs that otherwise would prove lethal for cells that are vulnerable.
To fight multidrug-resistant bacteria, a rapid antibiotic susceptibility testing (AST) has been developed and is currently tested in clinical trials. This test, called "nanomotion", is growth independent and measure vibrations of bacteria, which correlate with viability. Changes in nanomotion can be followed in real-time, and the impact of an antibiotic is assessed within minutes to hours, a significant saving intime compared to other ASTs.
Nanomotion has convincingly proved its efficacy in analyzing antibiotic susceptibility profiles of multiple bacteria. Nonetheless, it has never been used to measure either antibiotic tolerance of bacteria or the oscillations of fastidious and obligatory intracellular species such as the Chlamydia/es bacteria. ln the first part of this thesis, we measured the nanomotion signal of slow-growing Escherichia coli that are tolerant to 13-lactams and we noted that it furnishes insights into the bacteria phenotype and tolerance. Secondly, we developed a simple protocol to record specific nanomotion of elementary bodies, the extracellular infectious but non-dividing form of Chlamydia trachomatis and Waddlia chondrophi/a, two bacteria from the Chlamydia/es order. This is the first demonstration of elementary bodies nanomotion.
As a side project, we evaluated the efficacy of three distinct techniques (inclusion forming units counting, genome quantification and flow cytometry) for quantifying Chlamydia/es bacteria in a sample in order to emphasize their advantages and disadvantages. lndeed, depending on the different stages of their bacterial life cycle, bacteria are more accurately assessed through one procedure rather than another.
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07/06/2023 9:29
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08/06/2023 6:56
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