Investigation of antibiotic persistence mechanisms in Escherichia coli
Creators: name: Urbaniec, Joanna Wioletta
Publisher: name: University of Surrey
Year: 2023

description: Antibiotic persistence occurs when a subpopulation of isogenic, antibiotic sensitive cells
description: survives prolonged exposure to a bactericidal concentration of an antibiotic. This
description: phenomenon has been shown to contribute to prolonged treatment duration, infection
description: recurrence, as well as accelerated development of genetic resistance. Several molecular
description: mechanisms have been demonstrated to influence formation of persister cells, however,
description: the direct casual links between these mechanisms and persister cell formation remain to
description: be established.<br>
description: <br>
description: In this thesis we demonstrate that, contrary to previous reports, E. coli HipQ, a strain
description: created during an untargeted mutagenesis screen known to produce a high number of
description: antibiotic persisters, does not carry a mutation in the ydcI transcription factor.
description: Subsequently, we present evidence suggesting that ydcI does not regulate persistence
description: to β-lactams or fluoroquinolones. Furthermore, we show that the HipQ strain carries
description: multiple other non-synonymous substitutions, in contrast to previously reported two
description: single-nucleotide polymorphisms, including mutations in previously reported persistence
description: regulators, which are likely to contribute to its high-persistence phenotype.<br>
description: <br>
description: Next we demonstrate, with the use of flow cytometry and an [NADH:NAD+ biosensor],
description: that ciprofloxacin exposure results in a high number of viable but non culturable cells
description: (VBNCs). This ciprofloxacin-tolerant VBNC subpopulation has lower intracellular
description: [NADH:NAD+], and therefore undergoes respiration at a lower rate, when compared to
description: the bulk population. Furthermore, we show that E. coli HipQ antibiotic-tolerant cells have
description: a significantly lower intracellular [NADH:NAD+] when compared to its parental strain,
description: which likely is a result of a mutation in the glycolysis pathway gap gene.<br>
description: <br>
description: Finally, we assess antibiotic resistance, persistence and biofilm formation capabilities in
description: of a panel of urinary tract infection E. coli (UPEC) and demonstrate that in addition to
description: multidrug resistance, high-persistence to critically important antibiotics meropenem and
description: colistin is common amongst clinical isolates. We show that transient colistin resistance
description: develops rapidly when UPEC are incubated in in vivo mimicking conditions and that their
description: biofilm formation is dependent on attachment surface, with some isolates being able to
description: form biofilms on the surface of a uroepithelial cell monolayer, but not polystyrene.<br>
description: <br>
description: ‘Altogether, this thesis improves our understanding of molecular mechanisms regulating
description: the formation of E. coli antibiotic persisters, and further reaffirms the in-vivo relevancy of
description: persistence research.'<br>