Long-term systemic antibiotic therapy is used in either case; empiric therapy is initiated after intraoperative culture is done and usually combines coverage for methicillin-resistant gram-positive organisms (eg, vancomycin 1 g IV every 12 hours) and aerobic gram-negative organisms (eg, piperacillin / tazobactam 3.375 g IV every 6 hours or ceftazidime 2 g IV every 8 hours) and is revised based on results of culture and sensitivity testing.