Advanced Imaging for Detection of Foci of Infection in Staphylococcus aureus Bacteremia- Can a Scan Save Lives?

Abstract

Bloodstream infection or sepsis is a common cause of mortality globally. Staphylococcus aureus (S. aureus) is of particular concern, through its ability to seed metastatic infections in almost any organ after entering the bloodstream (S. aureus bacteraemia), often without localising signs. A positive blood culture for S. aureus bacteria should lead to immediate and urgent identification of the cause. Failure to detect a precise focus of infection is associated with higher mortality, sometimes despite appropriate antibiotics. This is likely due to the limited ability to effectively target therapy in occult lesions. Early detection of foci of metastatic S. aureus infection is therefore key for optimal diagnosis and subsequent therapeutic management. ¹⁸F-FDG-PET/CT and MRI offer us invaluable tools in the localisation of foci of S. aureus infection. Crucially, they may identify unexpected foci at previously unsuspected locations in the body, for example vertebral osteomyelitis in the absence of back pain. S. aureus bloodstream infections are further complicated by their microbiological recurrence; ¹⁸F-FDG-PET/CT provide a means of localising, thus enabling source control. More evidence is emerging as to the utility of ¹⁸F-FDG-PET/CT in this setting, perhaps even to the point of reducing mortality. ¹⁸ F-FDG-PET/MRI may have a similar impact. The available evidence demonstrates a need to investigate the impact of ¹⁸F-FDG-PET/CT and MRI scanning in clinical management and outcomes of S. aureus infection further in a randomised prospective clinical trial.

Figure 1

Mechanism of Staphylococcus aureus spread leading to deep and disseminated infection. (Color version of figure is available online.)

Figure 2

¹⁸F-FDG-PET/CT used to reveal occult foci of infection ¹⁸F-FDG-PET/CT was used to look for occult foci of infection in a case of recurrent S. aureus bacteraemia (A) This shows permanent implanted metal work in the right ribs and in the pelvis (B) This reveals possible foci of FDG avid infection at the right acromioclavicular joint and right ribs (C) FDG-avid bilateral sacroiliitis D: FDG-avid osteomyelitis of the pubic symphysis associated with metalwork. (Color version of figure is available online.)