Kenichi Okazaki

In this study, we evaluated the use of 15-(4-¹²³I-iodophenyl)-3(R,S)-methylpentadecanoic acid (¹²³I-BMIPP) to visualize fatty acid metabolism in bacteria for bacterial infection imaging. We found that ¹²³I-BMIPP, which is used for fatty acid metabolism scintigraphy in Japan, accumulated markedly in Escherichia coli EC-14 similar to ¹⁸F-FDG, which has previously been studied for bacterial imaging. To elucidate the underlying mechanism, we evaluated changes in ¹²³I-BMIPP accumulation under low-temperature conditions and in the presence of a CD36 inhibitor. The uptake of ¹²³I-BMIPP by EC-14 was mediated via the CD36-like fatty-acid-transporting membrane protein and accumulated by fatty acid metabolism. In model mice infected with EC-14, the biological distribution and whole-body imaging were assessed using ¹²³I-BMIPP and ¹⁸F-FDG. The ¹²³I-BMIPP biodistribution study showed that, 8 h after infection, the ratio of ¹²³I-BMIPP accumulated in infected muscle to that in control muscle was 1.31 at 60 min after ¹²³I-BMIPP injection. In whole-body imaging 1.5 h after ¹²³I-BMIPP administration and 9.5 h after infection, infected muscle exhibited a 1.33-times higher contrast than non-infected muscle. Thus, ¹²³I-BMIPP shows potential for visualizing fatty acid metabolism of bacteria for imaging bacterial infections.