Sulfonamides are best described as:

• A. Narrow spectrum antibiotics
• B. Broad spectrum antibiotics
• C. Antifungal agents
• D. Antiviral agents

Answer: (B)

Sulfonamides act as antibacterial agents by inhibiting a metabolic pathway that most bacteria rely on to make folic acid, which is essential for nucleotide production. Because this folic acid synthesis pathway is present in a wide variety of bacteria, sulfonamides have activity against many Gram-positive and Gram-negative organisms. That broad range of activity is what makes them broad-spectrum antibiotics. They are not antifungal or antiviral, since fungi and viruses require different targets, and sulfonamides don’t act on those types of pathogens. In addition, many sulfonamides are bacteriostatic—they stop growth rather than directly killing bacteria—and they’re sometimes used with trimethoprim to enhance effectiveness, reinforcing their broad reach across different bacteria.