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