<i>One problem is bacteria develop resistance to the new drugs very quickly. Usually within 2-3 years.</i><p>It actually varies significantly across antibiotics.  I can&#x27;t find the source right now, but there was a neat diagram that showed the introduction of each antibiotic and when resistance was first identified.<p>Some resistance was found in less than a year after the antibiotic was introduced and some were found 20 years later.