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

## TL;DR

This study used PET scans to track infection in rat vascular grafts, finding that FDG-PET can detect initial infection but not monitor its progression or treatment response.

## Contribution

The study demonstrates the limitations of FDG-PET in monitoring vascular graft infections over time and after antibiotic treatment.

## Key findings

- FDG-PET SUVmax was highest in untreated S. aureus-infected rats compared to other groups.
- Antibiotic-treated infected rats showed no difference in SUVmax from uninfected rats by day 31.
- Histology showed inflammation decreased over time with infection encapsulation and increased interleukin-10.

## Abstract

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.

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.

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.

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.