IMHO, D is the only correct choice. Nowhere in the passage we were told that antibiotics are the ONLY means to cure people. Therefore, we can infer that there are other, more beneficial, means to cure people -> don't give antibiotics to everyone who is sick, look for another treatment.
As for E, the author nowhere implies that if you change antibiotics patients will feel better. In fact the passage says that antibiotics in general (what actually means ANY of them) are bad. In this sense, it doesn't really make any difference whether you give one or another antibiotic to the patient - it will be bad anyway.