Talk about sulfa drugs.

Were the first drugs used in the 30s as antibiotics. They work on the metabolic pathway, they transform a molecule PABA to folic acid or tetra-hydro folic acid. We take our own folic acid from food (vitamin B9) but bacteria can synthesize its own folic acid by a multi-step process. The Sulfonamide work on one of the steps and another drug: Trimethoprim works on another enzyme