Mahmoud, Hadeel Ghazi Ahmed;
(2023)
Identification of Enterococcus faecium genes involved in resistance to oxidative stress and virulence.
Doctoral thesis (Ph.D), UCL (University College London).
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Abstract
The Enterococcus faecium clonal complex (CC17) is an example of how a cumulative evolutionary process improves relative fitness of bacteria in the hospital setting. As a result, a better knowledge of pathogen resistance mechanisms is required to forecast and prevent its spread. The research described here was aimed to test if zebrafish larvae and planarian infection models could be used to study the survival rates, colonisation, and pathogenicity of E. faecium E1162 and its isogenic mutants: 201c, 59N, Mabc, 183N, and 47N, which had transposon insertion in a gene that encoded respectively one of the following a serine/threonine protein kinase, a putative muramidase, a putative permease component of an ABC transporter, a cystathionine beta-synthase domain protein, and a putative tyrosine decarboxylase. In zebrafish larvae, mutants 201c, 59N, Mabc, and 183N were less virulent than E. faecium E1162. Killing was much later than E. faecium E1162 when planarians were co- incubated with mutants 59N, 47N and Δesp (deletion of the enterococcal surface protein gene). Also in this study the E. faecium E1162 transposon mutant library was screened for mutants with reduced oxidative stress sensitivity against superoxide generator menadione and/or the organic peroxide generator cumene hydroperoxide. Three mutants were identified: MS1 with an insertion in EfmE1162_1492 encoding a putative tyrosine decarboxylase involved in acid adaptation, MS2 with an insertion in Efm E1162_1516 encoding a putative conserved hypothetical protein, a tRNA-modifying enzyme, and MS3 with an insertion in efmE1162_2615 encoding a putative transposase a response stimulator. Mutant MS1 and MS2 were significantly more sensitive to 3.38 mM cumene hydroperoxide than E. faecium E1162. Compared to E. faecium E1162, the killing rate with MS2 decreased significantly in the first two days of infection in the Galleria mellonella (p > 0.025). In addition, mutant 59N was found to be more susceptible to menadione and cumene hydroperoxide than E. faecium E1162, and the wild-type virulence was restored in the G. mellonella infection model when mutant 59N was complemented in trans with the wild-type putative muramidase encoding gene. In conclusion, the genes mentioned above may play an important role in the pathogenesis of E. faecium infections. In addition, zebrafish larvae and planarian models are useful for studying E. faecium pathogenicity.
| Type: | Thesis (Doctoral) |
|---|---|
| Qualification: | Ph.D |
| Title: | Identification of Enterococcus faecium genes involved in resistance to oxidative stress and virulence |
| Open access status: | An open access version is available from UCL Discovery |
| Language: | English |
| Additional information: | Copyright © The Author 2022. Original content in this thesis is licensed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) Licence (https://creativecommons.org/licenses/by-nc/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author’s request. |
| UCL classification: | UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Medical Sciences UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Medical Sciences > Eastman Dental Institute UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Medical Sciences > Eastman Dental Institute > Microbial Diseases UCL |
| URI: | https://discovery-pp.ucl.ac.uk/id/eprint/10163896 |
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