- 10.00: Trial lecture
- 12.00: Public defence
You can also follow this event online (oslomet.zoom.us).
The webinar ID is 654 5406 4054 and the passcode is 0225.
The ordinary opponents are:
- First opponent: Associate Professor Denise C. Zysset-Burri, The University Hospital of Ophthalmology, Inselspital, Switzerland
- Second opponent: Associate Professor Pauline Cavanagh, UiT The Arctic University of Norway
- Leader of the committee: Associate Professor Yury Kiselev, OsloMet
The leader of the public defense is Head of Department Elin Holter Anthonisen, OsloMet.
The main supervisor is Professor Colin Charnock, OsloMet. The co-supervisors are Professor Tor Paaske Utheim, OsloMet and Professor Anis Yazidi, OsloMet.
Thesis abstract
The composition of the ocular microbiome, and the involvement of these microbes in ocular surface health and disease is an area of active research. Tear film hyperosmolarity initiates a cascade of events including inflammatory responses in dry eye disease (DED).
We hypothesized that the structure of and disturbances in the ocular microbiome may be important in the progress and symptoms of the disorder and aimed to characterize the ocular microbiome in dry eye patients and controls to see if leads concerning its potential involvement in the condition emerged.
Method
We recruited participants with clinically confirmed DED and healthy individuals and analysed, compared and contrasted their ocular microbiomes. Characterization was performed using both culture-dependent and culture-independent methods.
Both methods indicated that the ocular surface was mostly colonized by CoNS, Corynebacterium and Cutibacterium regardless of ocular health state. The opportunistic pathogens S. aureus and E. faecalis were also isolated from the ocular surface.
Species belonging to the Corynebacterium genus were characterized using WGS and phenotypic tests to examine their pathogenicity potential on the ocular surface. Their interaction with one another and other ocular bacteria was also investigated.
Furthermore, all isolates identified as S. aureus and as E. faecalis were investigated using WGS, in silico approaches to reveal pathogenicity and antibiotic susceptibility tests owing to their known associations with ocular infections.
Lastly, various supervised machine learning approaches were used to identify potential biomarkers of DED.
Findings
The work performed in this thesis supports previous finding regarding the ocular surface microbiome. It also extends the reach of previous work and suggests several new avenues of research, particularly with regard to ocular Corynebacterium.
The majority of the Corynebacterium species were found to have lipase and mucinase activity on agar, which could be clinically important.
Pertinently, some isolates were also found to inhibit other bacteria present on the ocular surface, which could have an impact on the ocular surface microbiome and its stability – and by extension its protective functions.
The interactions of Corynebacterium with immune cells and epithelial cell should be further investigated. Although S. aureus and E. faecalis were isolated from patients without ocular infections, the species did show virulence and pathogenicity potential.
The supervised ML models were able to distinguish between dry and healthy eyes based on the bacterial community and demonstrated an alternative hypothesis generating approach which can be used in future studies.
