What is the standard perioperative antibiotic for surgeries such as total knee replacement?

• A. Vancomycin
• B. Cefazolin
• C. Ciprofloxacin
• D. Aztreonam

Answer: (B)

Prophylaxis for clean orthopedic surgeries that involve implants targets the skin flora most likely to contaminate the wound, especially Staphylococcus species. Cefazolin, a first-generation cephalosporin, is the standard choice because it provides reliable coverage against Staphylococcus aureus and related skin flora, penetrates bone and soft tissues well, is safe, and is inexpensive. It is given within about an hour before the incision so adequate tissue levels are present when the surgery begins.

Vancomycin is reserved for patients with a penicillin allergy or known MRSA risk, but it carries slower onset and may not cover MSSA as effectively as cefazolin, so it’s not the default prophylaxis. Ciprofloxacin does not provide reliable coverage of Gram-positive skin flora, which are the primary concern in prosthetic joint infection, and aztreonam covers only Gram-negative organisms, missing the key Gram-positive pathogens. Therefore cefazolin is the standard perioperative antibiotic for surgeries like total knee replacement.