FDG-PET Imaging Tracks Acute Staphylococcus aureus Vascular Graft Infections in Rats

Overview

This study evaluated [18F]Fluorodeoxyglucose (FDG) PET imaging to identify and monitor vascular graft infections (VGEIs) caused by Staphylococcus aureus in a rat model. FDG uptake (SUVmax) was highest in untreated S. aureus infections but declined over time despite persistent bacterial load, limiting PET's ability to track infection progression or distinguish treated infections from uninfected grafts.

Background

Vascular graft infections are serious complications with high morbidity and mortality, commonly caused by Staphylococcus aureus and S. epidermidis. Diagnosis is challenging, and current standards involve surgical graft removal and prolonged antibiotics. FDG-PET/CT imaging is recommended by vascular surgery guidelines as a diagnostic tool based on metabolic activity around grafts. However, inflammation and noninfectious uptake can reduce diagnostic specificity, and the utility of FDG-PET for monitoring treatment response remains unclear. Animal models are essential to better understand infection dynamics and imaging performance.

Data Highlights

Key Findings

• FDG-PET SUVmax was significantly elevated in untreated S. aureus-infected rats compared to uninfected controls early after surgery.
• SUVmax declined over time in all groups, including untreated infections, despite persistent bacterial presence.
• Antibiotic-treated S. aureus-infected rats showed SUVmax values comparable to uninfected rats by day 31, despite ongoing infection.
• Histology revealed intense inflammation at day 10 in S. aureus infections, which decreased by days 20 and 31 with infection encapsulation and increased anti-inflammatory IL-10.
• FDG-PET could differentiate untreated infections from uninfected grafts but failed to monitor infection progression or treatment response accurately.

Clinical Implications

FDG-PET imaging can aid in the early diagnosis of acute S. aureus vascular graft infections by detecting increased metabolic activity. However, its declining uptake over time despite persistent infection limits its utility for monitoring treatment response or infection progression. Clinicians should interpret FDG-PET results cautiously, especially when assessing infection resolution after antibiotic therapy, as reduced inflammation and encapsulation may mask ongoing infection.

Conclusion

FDG-PET is effective for identifying acute untreated S. aureus vascular graft infections but is insufficient for tracking infection progression or confirming eradication post-treatment due to declining inflammatory signals despite persistent bacterial load.

References

1. Sunde et al. 2021 -- FDG-PET/CT in diagnosing vascular graft infections
2. Husmann et al. 2019 -- PET/CT for monitoring antimicrobial therapy in VGEI
3. European Society for Vascular Surgery 2020 -- MAGIC criteria for VGEI diagnosis