No need for broad-spectrum empirical antibiotic coverage after surgical drainage of orthopaedic implant infections

Purpose: Empirical broad-spectrum antibiotic treatment for orthopaedic implant infections after surgical lavage is common practice while awaiting microbiological results, but lacks evidence. Methods: This was a single-centre cohort study from 1996 to 2010 with a follow-up of twoyears. Results: We retrieved 342 implant infections and followed them up for a median of 3.5years (61 recurred, 18%). Infected implants were arthroplasties (n = 186), different plates, nails or other osteosyntheses. The main pathogens were S. aureus (163, 49 methicillin-resistant) and coagulase-negative staphylococci (60, 45 methicillin-resistant). Median duration of empirical antibiotic coverage after surgical drainage was threedays before switching to targeted therapy. Vancomycin was the most frequent initial empirical agent (147), followed by intravenous co-amoxiclav (44). Most empirical antibiotic regimens (269, 79%) proved sensitive to the causative pathogen, but were too broad in 111 episodes (32%). Cephalosporins and penicillins were used only in 44 and ten cases, respectively, although they would have covered 59% of causative pathogens identified later. Multivariate Cox regression analysis showed that neither susceptible antibiotic coverage (compared to non-susceptible; hazard ratio 0.7, 95% confidence interval 0.4-1.2) nor broad-spectrum use (hazard ratio 1.1, 0.8-1.5) changed remission rates. Conclusions: Provided that surgical drainage is performed, broad-spectrum antibiotic coverage does not enhance remission of orthopaedic implant infections during the first threedays. If empirical agents are prescribed from the first day of infection, narrow-spectrum penicillins or cephalosporins can be considered to avoid unnecessary broad-spectrum antibiotic us