Ampicillin/Sulbactam 24-Hour Postoperative Prophylaxis

The goal of this clinical trial is to learn whether giving antibiotics for 7 days after surgery, instead of the usual 24 hours, lowers the chance of wound infection in adults having major surgery for mouth or throat cancer. This includes operations that rebuild the area with tissue taken from another part of the body (free-flap reconstruction). The main question it aims to answer is: Does a 7-day course of antibiotics after surgery lower the number of patients who get a surgical wound infection within 30 days, compared with the standard 24-hour course? Other questions are: Does the longer course shorten the time spent in the intensive care unit and in the hospital? Does it lower the number of emergency room visits, hospital readmissions, and hospital costs within 30 days? Is the longer course safe, and does it cause more side effects? Researchers will compare two groups. Both groups receive the same antibiotic (ampicillin/sulbactam) through a vein before and during surgery. After surgery, one group continues the antibiotic for 24 hours (the current standard), and the other group continues it for 7 days, or until they go home if that is sooner. Participants will: Be assigned by chance (like flipping a coin) to one of the two groups Follow the hospital's usual care before surgery, including mouthwash, antiseptic body wash, and nasal ointment for 5 days Receive the antibiotic according to their group Be followed for 30 days after surgery to check for wound infection, other complications, return visits, and readmissions