Comparison of 99mTc- and 18F-ubiquicidin autoradiography to anti-Staphylococcus aureus immunofluorescence in rat muscle abscesses.

Abstract

99mTc-ubiquicidin (UBI) 29-41 is under clinical evaluation for discrimination between bacterial infection and unspecific inflammation. We compared the distribution of 99mTc-UBI 29-41, the potential PET tracers 18F-UBI 29-41 and 18F-UBI 28-41, and 3H-deoxyglucose (DG) in rat muscle abscesses to that of anti-Staphylococcus aureus immunofluorescent imaging. Calf abscesses were induced in 15 CDF-Fischer rats after inoculation of Staphylococcus aureus. One to 6 d later, either 18F-UBI 29-41 and 3H-DG (n = 5) or 18F-UBI 28-41 and 3H-DG (n = 6) or 99mTc-UBI 29-41 and 3H-DG (n = 4) were injected simultaneously. Dual-tracer autoradiography of the abscess area was compared with the distribution of bacteria and macrophages. The UBI derivates exhibited increased uptake in the abscess area that partly matched 3H-DG uptake and macrophage infiltration but showed no congruity with areas that were highly positive for bacteria. A specific binding of UBI derivatives to Staphylococcus aureus in vivo could not be confirmed in this study.