Comparison of L- and D-Amino Acids for Bacterial Imaging in Lung Infection Mouse Model

The effectiveness of L- and D-amino acids for detecting the early stage of infection in bacterial imaging was compared. We evaluated the accumulation of H-3-L-methionine (Met), H-3-D-Met, H-3-L-alanine (Ala), and H-3-D-Ala in E. coli EC-14 and HaCaT cells. Biological distribution was assessed in control and lung-infection-model mice with EC-14 using H-3-L- and D-Met, and F-18-FDG. A maximum accumulation of H-3-L- and D-Met, and H-3-L- and D-Ala occurred in the growth phase of EC-14 in vitro. The accumulation of H-3-L-Met and L-Ala was greater than that of H-3-D-Met and D-Ala in both EC-14 and HaCaT cells. For all radiotracers, the accumulation was greater in EC-14 than in HaCaT cells at early time points. The accumulation was identified at 5 min after injection in EC-14, whereas the accumulation gradually increased in HaCaT cells over time. There was little difference in biodistribution between H-3-L-and D-Met except in the brain. H-3-L- and D-Met were sensitive for detecting areas of infection after the spread of bacteria throughout the body, whereas F-18-FDG mainly detected primary infection areas. Therefore, C-11-L- and D-Met, radioisotopes that differ only in terms of H-3 labeling, could be superior to F-18-FDG for detecting bacterial infection in lung-infection-model mice.