A 70-year-old woman develops a periprosthetic joint infection 6 months after total knee replacement. Intraoperative tissue cultures grow Staphylococcus epidermidis. The primary reason antibiotic therapy alone fails to eradicate the infection is:
- A The organism produces beta-lactamase enzymes
- B S. epidermidis is inherently resistant to all standard antibiotics
- C Biofilm formation on the implant surface prevents antibiotic penetration ✓
- D Poor vascular supply around the prosthesis limits drug delivery
Correct answer: C. Biofilm formation on the implant surface prevents antibiotic penetration
Explanation
Biofilm formation is the hallmark of periprosthetic joint infection. Bacteria adhere to the implant surface and produce an extracellular polymeric substance matrix that shields them from both antibiotics and host immune cells. This is why surgical intervention, typically debridement with implant retention or staged revision, is required. Beta-lactamase production occurs but is not the primary reason for treatment failure.
Reference: Rockwood and Green's Fractures in Adults, 9th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.