George is a healthy 28-year-old man. He enjoys an active lifestyle, including playing on an intramural Ultimate Frisbee team. Last weekend, while at a meet, George got a cut on his leg, just above the knee. It wasn’t very deep, and he cleaned the wound thoroughly when he got home. A few days later, the cut didn’t seem to be healing as George would have expected. It was a little sore, and he was worried that it might have been infected, so he decided to go his local outpatient clinic to have it examined. At the clinic, Dr. Smith examines the wound. He tells George that it looks like it might be infected, so he prescribes a broad-spectrum antibiotic, tells George to keep the wound clean, and sends him home. Over the next week, George becomes concerned when the wound doesn’t get any better—in fact, it starts to get worse. The affected area has become larger, and it is sorer than it was earlier.

Required:
What do you think is responsible for the infection knowing that antibiotics have been used?