How long for strep throat to resolve?

Patient: My husband has a nasty case of strep throat. Lesions in his throat and puss-filled blisters in his throat. Keflex 500 mg BID was prescribed, and he took the first dose on Tuesday. How long should it take for the blisters to resolve? They still look pretty bad after 4 doses of antibiotic.

Symptoms: Very sore throat, fever (fever is better today)