E-Thesis 40 views 23 downloads
Conditions for biofilm formation in Extraintestinal Pathogenic E. coli (ExPEC) / Martynas Basevicius
Swansea University Author: Martynas Basevicius
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...
| 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 |
| 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 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. |
|---|---|
| Item Description: |
ORCiD identifier: https://orcid.org/0009-0003-9833-5115 |
| Keywords: |
Sepsis, E. coli, Biofilm, Bile salts |
| College: |
Faculty of Medicine, Health and Life Sciences |