A patient presents with a community-acquired uncomplicated urinary tract infection most likely due to E. coli. Which statement best describes the rationale for using sulfamethoxazole–trimethoprim (Bactrim) in this setting today?

• A. Sulfamethoxazole–trimethoprim provides broad-spectrum activity against typical UTI pathogens and the combination is synergistic, often allowing lower doses and a practical treatment option when local resistance rates are acceptable.
• B. Sulfamethoxazole–trimethoprim is preferred because it is a topical antifungal that also sterilizes the urinary tract and is therefore better than antibiotics targeting folate synthesis.
• C. Sulfamethoxazole alone without trimethoprim is sufficient for empirical UTI therapy because the addition of trimethoprim would antagonize sulfonamide activity and reduce clinical efficacy.
• D. Sulfamethoxazole–trimethoprim should never be used for UTIs because sulfonamides have no activity against gram-negative bacteria including E. coli.

Answer: (A)