18-Fluoro-2-deoxy-d-glucose positron emission tomography/computed tomography scan for monitoring the therapeutic response in experimental Staphylococcus aureus foreign-body osteomyelitis

Background: 18-Fluoro-2-deoxy-d-glucose positron emission tomography combined with computed tomography (18F-FDG PET/CT) scan is useful for diagnosis of osteoarticular infections. Whether 18F-FDG PET/CT scanning may be used for therapeutic monitoring is not clear. The objective of this study was to develop 18F-FDG PET/CT scanning for monitoring therapeutic response to antimicrobials in experimental Staphylococcus aureus osteomyelitis. Methods: A total of 22 rabbits were studied. In 20 animals, the right tibia was inoculated intraoperatively with S. aureus. Two control animals were inoculated with normal saline. A needle was placed in the tibia as a foreign body. Infection was allowed to develop for 21 days when 18F-FDG PET/CT was performed, the needle was removed, and bone specimens were cultured to confirm infection. Antimicrobial therapy with daptomycin was initiated in all successfully infected animals for 1, 3, or 6 weeks. Following completion of treatment, a second 18F-FDG PET/CT was performed, animals were euthanized, and infected tibias were harvested for quantitative cultures and histology. A positive scan was defined as 18F-FDG signal activity greater in the infected tibia than that of the contralateral non-infected control tibia. Therapeutic response was measured by the change of 18F-FDG signal activity in the infected tibia. Results: All successfully infected animals (n=14), with microbiologically and/or histologically confirmed osteomyelitis, had positive 18F-FDG PET/CT scans, while the two control animals had negative scans despite the presence of the foreign body [mean maximum standardized uptake value (SUVmax) (±SD) values 2.96 (±0.80) vs. 1 (±1.10), respectively, P=0.04]. In the 14 successfully infected animals, the mean SUVmax was significantly higher in the infected compared to the uninfected tibia (P