[18F]Fluorodeoxyglucose Positron Emission Tomography for Diagnosis and Monitoring of Acute Staphylococcus aureus Vascular Graft Infection in a Rat Model.

Abstract

OBJECTIVES: Vascular graft or endograft infections (VGEIs) pose a detrimental complication when using vascular grafts and are challenging to diagnose and treat. This study examined the progression of infection and the antimicrobial response in VGEI using [18F]Fluorodeoxyglucose (chemical name, 2-Deoxy-2-[18F]fluoroglucose) (FDG) positron emission tomography (PET), ex vivo bacterial quantification, and histology in a VGEI rat model. METHODS: In this experimental study, 97 male Sprague-Dawley rats had a polytetrafluorethylene graft surgically implanted in the carotid artery. The graft was either preinoculated with Staphylococcus aureus, S. epidermidis, or saline. Up to 31 days after surgery, rats were FDG-PET-scanned. Subsequently, they were killed, and the implants were retrieved for analysis. A subgroup of infected rats received daptomycin and rifampicin from days 20 to 29. RESULTS: Tracer uptake around the implant, measured by maximum standardized uptake value (SUVmax), declined over time in all groups. Between groups, SUVmax was highest in untreated S. aureus-infected rats. When comparing antibiotic-treated and uninfected rats by day 31, there was no difference in SUVmax, although the treated rats were still infected. Histology revealed widespread inflammation by day 10 in S. aureus-infected rats, which decreased by days 20 and 31 with encapsulation of the infection, alongside increased plasma interleukin-10. CONCLUSIONS: FDG-PET differentiated untreated S. aureus-infected rats from uninfected ones but failed to monitor infection progression, as SUVmax declined over time despite a constant bacterial load. FDG-PET could not distinguish between uninfected rats and those with suppressed infection, likely due to reduced inflammation and encapsulation of the infection.