A patient suffered a torn Achilles tendon while playing flag football with some friends. He underwent an Achilles tendon repair, and 10 days postoperatively, he noticed swelling, redness, and warmth around the incision and yellow discharge seeping from it. What would the patient's physician use to determine the appropriate antibiotic therapy?

a) CBC with differential test
b) Culture and sensitivity
c) Serum creatinine
d) Empirical evidence test