USMLE Step 2 Antibiotics and Treatments Practice Exam

Sulfonamides are a class of antibiotics that function primarily through the inhibition of folic acid synthesis. These medications achieve this by mimicking para-aminobenzoic acid (PABA), which is a precursor in the bacterial synthesis pathway of folate. Bacteria require folic acid for the synthesis of nucleic acids and ultimately for their growth and replication.

When sulfonamides inhibit the action of an enzyme called dihydropteroate synthase, this leads to a reduced availability of folate, which subsequently disrupts DNA and RNA synthesis, thereby inhibiting bacterial growth. This mechanism highlights the unique aspect of sulfonamides targeting a metabolic pathway rather than direct cell wall or protein synthesis, which are mechanisms seen with other classes of antibiotics.

Folic acid synthesis is crucial for many microorganisms but is not a process present in human cells, making sulfonamides effective with relatively less toxicity to humans. This specificity is an essential aspect of their therapeutic use and contributes to their role in treating various bacterial infections.