Imaging of a localized bacterial infection with endogenous thymidine kinase using radioisotope-labeled nucleosides.

Su Jin Jang, Yong Jin Lee, Sangyong Lim, Kwang Il Kim, Kyo Chul Lee, Gwang Il An, Tae Sup Lee, Gi Jeong Cheon, Sang Moo Lim, Joo Hyun Kang

Index: Int. J. Med. Microbiol. 302(2) , 101-7, (2012)

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Abstract

The importance of noninvasive imaging methods to bacterial infections is widely recognized. To obtain bacterial infection imaging with radioisotope-labeled nucleosides, bacterial thymidine kinase (tk) activities of Salmonella typhimurium with [(125)I]5-iodo-1-(2'-fluoro-2'-deoxy-β-d-arabinofuranosyl)uracil ([(125)I]FIAU) or 3'-deoxy-3'-[(18)F]fluorothymidine ([(18)F]FLT) were measured. The infection model in BALB/c mice was imaged with [(125)I]FIAU or [(18)F]FLT using small-animal Single Photon Emission Computed Tomography (SPECT) or Positron Emission Tomography (PET), respectively. The accumulated radioactivity of [(125)I]FIAU or [(18)F]FLT in the two strains showed a linearly increased pattern with increasing incubation time or bacterial numbers. The image clearly demonstrated a high uptake of [(125)I]FIAU and [(18)F]FLT in the bacterial infection site. [(18)F]FLT uptake in the infection site of was 7.286±2.405, whereas that in the uninfected site was 0.519±0.561. The relative activity ratio of the infected region in relation to the uninfected region was 2.98 at 4h after an injection with [(125)I]FIAU determined by biodistribution data. In conclusion, the bacterial tk activity was confirmed by the cellular uptake and imaging with [(125)I]FIAU or [(18)F]FLT. Therefore, a localized bacterial infection in living mice can be monitored using radioisotope-labeled nucleosides with a nuclear medicine imaging modality.Copyright © 2012 Elsevier GmbH. All rights reserved.