Cefazolin
Cefazolin is the drug of choice for prophylaxis in cardiac surgery because: 1) It is a first-generation cephalosporin with excellent coverage against Staphylococcus aureus (including MSSA) and Staphylococcus epidermidis - the most common organisms causing surgical site infections in cardiac surgery, 2) It has good tissue penetration, 3) Appropriate half-life for surgical prophylaxis, 4) It should be administered within 60 minutes before skin incision. For patients with β-lactam allergy, vancomycin is an alternative.