Each and every time bacteria get exposed to an antibiotic, a selection pressure towards mutations conferring bacterial resistance works to create antibiotic resistance overtime. Bacteria with gene mutations helping them survive the antibiotic live on and pass these genes to other bacteria. Darwin works in the bugs' favor. This is why it's important we use antibiotics only when necessary – and when we do use them, that we use the most appropriate antibiotic for the infection at hand. 📸: US Center for Disease Control and Prevention