If a patient is allergic to cephalosporins, which antibiotic is used for surgical prophylaxis?

• A. Vancomycin
• B. Penicillin
• C. Aztreonam
• D. Levofloxacin

Answer: (A)

In surgical prophylaxis for someone with a cephalosporin allergy, you choose an antibiotic that covers the most likely wound pathogens without using a beta-lactam. Vancomycin is ideal here because it provides strong coverage against Gram-positive organisms, including MRSA, and it is not a beta-lactam, so it avoids any cross-sensitivity concerns with cephalosporins. While penicillin is a beta-lactam and would be avoided in this setting due to the allergy, aztreonam mainly covers Gram-negative bacteria and does not reliably cover Staphylococcus aureus, which is a common cause of surgical site infections. Levofloxacin has activity against some Gram-negatives and Gram-positives but is not preferred for routine prophylaxis due to resistance concerns and spectrum limitations. Thus vancomycin best meets the need to prevent infection when cephalosporins cannot be used.