Introduction

Coagulase-negative staphylococci, including S. epidermidis, have emerged as the leading pathogen of nosocomial (hospital-acquired) biomaterial-related infections, including periprosthetic infections and intravascular catheter-related bloodstream infections. Pathogenic S. epidermidis strains exhibit robust attachment to implant surfaces and subsequent biofilm formation. By nature, the clinical picture of periprosthetic S. epidermidis infections can be indolent with vague signs of infection. These infections are also highly challenging for diagnostic imaging and microbiologic studies. Our recent experimental study of ¹⁸F-FDG-PET/CT confirmed that subacute peri-implant S. epidermidis infections, reflecting limited inflammatory reaction, are characterised by low ¹⁸F-FDG uptake. Vascular adhesion protein-1 (VAP-1) is an inflammation inducible endothelial protein, which controls leukocyte migration to sites of inflammation and infection. Siglec-9 is a leukocyte ligand of VAP-1. We hypothesised that ⁶⁸Ga-labeled Siglec-9, developed for PET imaging of inflammation and cancer, could be a novel tracer also for early defection of S. epidermidis peri-implant bone infections.