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Conditions for biofilm formation in Extraintestinal Pathogenic E. coli (ExPEC) / Martynas Basevicius

Swansea University Author: Martynas Basevicius

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Abstract

Sepsis is a complex multi-organ state caused by a dysfunctional immune response to infection. Recent estimates suggest an incidence of around 360 cases per 100,000 population per year, resulting in approximately 20% of all mortality rates. Bacteria cause about 70% of sepsis cases, with extrapathogen...

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Published: Swansea, Wales, UK 2025
Institution: Swansea University
Degree level: Master of Research
Degree name: MSc by Research
Supervisor: Wilkinson, Thomas S. ; Harris, Llinos G.
URI: https://cronfa.swan.ac.uk/Record/cronfa69889
first_indexed 2025-07-03T16:09:22Z
last_indexed 2025-07-04T06:42:56Z
id cronfa69889
recordtype RisThesis
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spelling 2025-07-03T17:14:47.7395555 v2 69889 2025-07-03 Conditions for biofilm formation in Extraintestinal Pathogenic E. coli (ExPEC) f3642a8413f4588e85fc4f380712e344 Martynas Basevicius Martynas Basevicius true false 2025-07-03 MEDS Sepsis is a complex multi-organ state caused by a dysfunctional immune response to infection. Recent estimates suggest an incidence of around 360 cases per 100,000 population per year, resulting in approximately 20% of all mortality rates. Bacteria cause about 70% of sepsis cases, with extrapathogenic Escherichia coli (ExPEC) being a major contributor locally in the Hywel Dda University Health Board (HDUHB). ExPEC utilise various virulence factors (VF) to evade the immune system. Some of these are responsible for producing biofilms, which are aggregates of bacteria, providing protection in diverse environments, but less work has focused on parameters of biofilm formation in ExPEC. This thesis aimed to identify optimal conditions for biofilm formation in ExPEC strains, then use these conditions to implicate phenotypes, genes and visualise structure in the biofilm formation process. Blood culture-positive E. coli isolates from HDUHB were used in growth and biofilm assays. Phenotypic, clinical and sequence metadata was used for isolate comparisons, while imaging experiments were performed using confocal laser scanning microscopy (CLSM). The optimal parameters needed for biofilm formation in ExPEC were Luria Bertani, Tryptic Soy Broth+Glucose or Escherichia Coli broth, 24-hour pre-culture and bile salts. Sequence type 73 (ST73) isolates had significantly higher biofilm levels than ST131 isolates. Subsequently, fimACDFGHI, rcsAB and acrE genes were associated with biofilm formation in ExPEC bacteraemia strains. CLSM confirmed live biofilms with significant biomass and thickness in both biofilm-positive and negative isolates. This work demonstrated the requirement of bile salts for biofilm formation in ExPEC, while iron supplementation had no effect. It also identified potential list of biofilm-promoting genes in ExPEC, requiring functional confirmation in knockout mutants and visualisation in live biofilm structures. In conclusion, this work will enhance the understanding of ExPEC pathogenesis and contribute to biomarker identification to predict severe infections using optimised methods for gene identification. E-Thesis Swansea, Wales, UK Sepsis, E. coli, Biofilm, Bile salts 27 6 2025 2025-06-27 ORCiD identifier: https://orcid.org/0009-0003-9833-5115 COLLEGE NANME Medical School COLLEGE CODE MEDS Swansea University Wilkinson, Thomas S. ; Harris, Llinos G. Master of Research MSc by Research 2025-07-03T17:14:47.7395555 2025-07-03T17:05:47.2439192 Faculty of Medicine, Health and Life Sciences Swansea University Medical School - Biomedical Science Martynas Basevicius 1 69889__34672__e7c93abce1b14bb997d5abaf76fad5e4.pdf Basevicius_Martynas_MSc_Research_Thesis_Final_Cronfa.pdf 2025-07-03T17:13:23.0882170 Output 2837825 application/pdf E-Thesis – open access true Copyright: The Author, Martynas Basevicius, 2025. true eng
title Conditions for biofilm formation in Extraintestinal Pathogenic E. coli (ExPEC)
spellingShingle Conditions for biofilm formation in Extraintestinal Pathogenic E. coli (ExPEC)
Martynas Basevicius
title_short Conditions for biofilm formation in Extraintestinal Pathogenic E. coli (ExPEC)
title_full Conditions for biofilm formation in Extraintestinal Pathogenic E. coli (ExPEC)
title_fullStr Conditions for biofilm formation in Extraintestinal Pathogenic E. coli (ExPEC)
title_full_unstemmed Conditions for biofilm formation in Extraintestinal Pathogenic E. coli (ExPEC)
title_sort Conditions for biofilm formation in Extraintestinal Pathogenic E. coli (ExPEC)
author_id_str_mv f3642a8413f4588e85fc4f380712e344
author_id_fullname_str_mv f3642a8413f4588e85fc4f380712e344_***_Martynas Basevicius
author Martynas Basevicius
author2 Martynas Basevicius
format E-Thesis
publishDate 2025
institution Swansea University
college_str Faculty of Medicine, Health and Life Sciences
hierarchytype
hierarchy_top_id facultyofmedicinehealthandlifesciences
hierarchy_top_title Faculty of Medicine, Health and Life Sciences
hierarchy_parent_id facultyofmedicinehealthandlifesciences
hierarchy_parent_title Faculty of Medicine, Health and Life Sciences
department_str Swansea University Medical School - Biomedical Science{{{_:::_}}}Faculty of Medicine, Health and Life Sciences{{{_:::_}}}Swansea University Medical School - Biomedical Science
document_store_str 1
active_str 0
description Sepsis is a complex multi-organ state caused by a dysfunctional immune response to infection. Recent estimates suggest an incidence of around 360 cases per 100,000 population per year, resulting in approximately 20% of all mortality rates. Bacteria cause about 70% of sepsis cases, with extrapathogenic Escherichia coli (ExPEC) being a major contributor locally in the Hywel Dda University Health Board (HDUHB). ExPEC utilise various virulence factors (VF) to evade the immune system. Some of these are responsible for producing biofilms, which are aggregates of bacteria, providing protection in diverse environments, but less work has focused on parameters of biofilm formation in ExPEC. This thesis aimed to identify optimal conditions for biofilm formation in ExPEC strains, then use these conditions to implicate phenotypes, genes and visualise structure in the biofilm formation process. Blood culture-positive E. coli isolates from HDUHB were used in growth and biofilm assays. Phenotypic, clinical and sequence metadata was used for isolate comparisons, while imaging experiments were performed using confocal laser scanning microscopy (CLSM). The optimal parameters needed for biofilm formation in ExPEC were Luria Bertani, Tryptic Soy Broth+Glucose or Escherichia Coli broth, 24-hour pre-culture and bile salts. Sequence type 73 (ST73) isolates had significantly higher biofilm levels than ST131 isolates. Subsequently, fimACDFGHI, rcsAB and acrE genes were associated with biofilm formation in ExPEC bacteraemia strains. CLSM confirmed live biofilms with significant biomass and thickness in both biofilm-positive and negative isolates. This work demonstrated the requirement of bile salts for biofilm formation in ExPEC, while iron supplementation had no effect. It also identified potential list of biofilm-promoting genes in ExPEC, requiring functional confirmation in knockout mutants and visualisation in live biofilm structures. In conclusion, this work will enhance the understanding of ExPEC pathogenesis and contribute to biomarker identification to predict severe infections using optimised methods for gene identification.
published_date 2025-06-27T05:47:08Z
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score 11.101457

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