The causes of antibiotic resistance are often complex and it is difficult to identify strategies to prevent or delay its emergence. One strategy has been to use less active members of a drug class, so that when resistance develops the more active members will still prevail. This strategy may often fail because this resistance may form the basis of resistance to the whole class. Often, less active drugs are the first to be discovered and more active versions follow, so we have had no choice; however, increasingly less active drugs are available to deal with specific infections and this may have a detrimental effect on the class as a whole.