Prevention of Propionibacterium acnes biofilm formation in prosthetic infections in vitro

Abstract

Background: The role of Propionibacterium acnes in shoulder arthroplasty and broadly in orthopaedic prosthetic infections (PIs) has historically been underestimated, with biofilm formation identified as a key virulence factor attributed to invasive isolates. With an often indolent clinical course, P. acnes infection can be difficult to detect and treat. The present study investigates absorbable cements loaded with a broad-spectrum antibiotic combination as an effective preventative strategy to combat P. acnes biofilms.

Methods: P. acnes biofilm formation on an unloaded synthetic calcium sulfate (CaSO₄) bone void filler cement bead was evaluated by scanning electron microscopy (SEM) over 14 days. Beads loaded with tobramycin alone, vancomycin alone (as comparative controls) and a vancomycin & tobramycin dual treatment were assessed for their ability to eradicate planktonic P. acnes, prevent biofilm formation and eradicate preformed biofilms was also evaluated using viable cell counts, confocal microscopy and SEM.

Results: P. acnes surface colonisation and biofilm formation on unloaded CaSO₄ beads was slow. Beads loaded with antibiotics were able to kill planktonic cultures of 106 CFU/ml, prevent bacterial colonisation and significantly reduce biofilm formation over periods of weeks. Complete eradication of established biofilms was achieved with a contact time of one week.

Conclusions: This study demonstrates that antibiotic-loaded CaSO₄ beads may represent an effective antibacterial and antibiofilm strategy to combat PIs in which P. acnes is involved.

Level of Evidence: Basic Science Study

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Identifiers

ORCID for Jeremy Webb: orcid.org/0000-0003-2068-8589

ORCID for Paul Stoodley: orcid.org/0000-0001-6069-273X

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