Antibiotic Resistance: Evolution Strikes Back

Even as antibiotics saved millions, scientists warned of a problem. In his 1945 Nobel lecture, Alexander Fleming cautioned that underdosing could allow bacteria to become resistant. Bacteria reproduce rapidly, and when antibiotics kill susceptible strains, resistant ones survive and spread, an example of natural selection. Overuse in medicine and agriculture accelerates this process. Methicillin-resistant Staphylococcus aureus (MRSA) was identified in Britain in 1961, just after methicillin came into use.

A study published in The Lancet in 2022 estimated that bacterial antimicrobial resistance directly caused about 1. 27 million deaths in 2019. Meanwhile, few new classes of antibiotics have been discovered since the 1980s, partly because they are less profitable than drugs taken for years. The WHO adopted a global action plan in 2015. Antibiotic resistance shows how a technology's success can erode itself and why responses require coordinated action across countries.