Immunoproteomic Identification ofIn Vivo-Produced Propionibacterium acnes Proteins in a Rabbit Biofilm Infection Model

Abstract

ABSTRACTPropionibacterium acnesis well-known as a human skin commensal but can also act as an invasive pathogen causing implant-associated infections. In order to resolve these types ofP. acnesinfections, the implants must be removed, due to the presence of an established biofilm that is recalcitrant to antibiotic therapy. In order to identify thoseP. acnesproteins producedin vivoduring a biofilm infection, we established a rabbit model of implant-associated infection with this pathogen.P. acnesbiofilms were anaerobically grown on dextran beads that were then inoculated into the left tibias of rabbits. At 4 weeks postinoculation,P. acnesinfection was confirmed by radiograph, histology, culture, and PCR.In vivo-produced and immunogenicP. acnesproteins were detected on Western blot using serum samples from rabbits infected withP. acnesafter these bacterial proteins were separated by two-dimensional gel electrophoresis. Those proteins that bound host antibodies were then isolated and identified by tandem mass spectrometry. Radiographs and histology demonstrated a disruption in the normal bone architecture and adherent biofilm communities in those animals with confirmed infections. A total of 24 immunogenic proteins were identified; 13 of these proteins were upregulated in both planktonic and biofilm modes, including an ABC transporter protein. We successfully adapted a rabbit model of implant-associated infection forP. acnesto identifyP. acnesproteins produced during a chronic biofilm-mediated infection. Further studies are needed to evaluate the potential of these proteins for either a diagnostic test or a vaccine to prevent biofilm infections caused byP. acnes.