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Title: Molecular imaging of Staphylococcus aureus infections
Author: Mills , Bethany
ISNI:       0000 0004 6425 144X
Awarding Body: University of Nottingham
Current Institution: University of Nottingham
Date of Award: 2015
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Molecular imaging provides a less invasive means for studying bacterial infections in vivo compared to traditional techniques. However, molecular imaging of infection is currently limited due the lack of suitable imaging tracers. The most widely adopted approach for studying Staphylococcus aureus infections utilises a recombinant bioluminescent strain. However, several environmental requirements and signal attenuation through host tissue render this approach unsuitable for several applications. In order to provide an alternative research tool, the use of SNAP-tag, CLIP-tag and HaloTag was explored. Once expressed, these tags specifically bind fluorescent ligands. The tags were expressed via an inducible plasmid based system, and engineered to covalently attach to the cell surface of S. aureus. The function of the tags was validated in vitro by fluorescence imaging. SNAP-tag was subsequently incorporated into the genome of bioluminescent S. aureus Xen29. This thesis presents the first demonstration of visualising SNAP-tag expressing bacteria in vivo by fluorescent imaging. Potential applications for SNAP-tag imaging were then investigated; such as screening antimicrobials. Imaging of SNAP-tag expressing S. aureus was shown to provide additional information about the infection site compared to bioluminescence imaging alone. Novel [99mTc] SNAP-tag ligands were then developed and evaluated to provide a means for nuclear imaging of SNAP-tag. In addition, tools for infection diagnosis by nuclear imaging currently rely on targeting host immune responses rather than the bacteria directly; resulting in a high false positive rate. In order to develop a tracer with clinical potential to detect infection and not inflammation, the bacterial Universal Hexose Phosphate Transporter (UHPT) was selected as a target. [18F]FDG is an analogue of glucose and is widely used within nuclear medicine. [18F]FDG was phosphorylated, making it a substrate for UHPT. Validations in vitro suggested this probe may be a good tool for specific S. aureus detection; however in vivo biodistribution rendered it an unsuitable candidate.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available