Bacteria aren't resistant to a drug. They're resistant to a mechanism of action. For example, bacteria develop beta-lactamase based resistance, which can make t

Bacteria aren't resistant to a drug. They're resistant to a mechanism of action. For example, bacteria develop beta-lactamase based resistance, which can make them resistant to all beta-lactam antibiotics, which is any antibiotic with -illin in the name. You'd potentially have to take whole classes of antibiotics out of circulation, for a long time. And even then, some of them will maintain resistance genes because these compounds are present in the environment.