Sulfamethoxazole

Definition

Sulfamethoxazole is a sulfonamide antibiotic that inhibits bacterial synthesis of dihydrofolic acid by competing with para-aminobenzoic acid (PABA). It is often used in combination with trimethoprim to treat various bacterial infections, including those of the urinary tract.

5 Must Know Facts For Your Next Test

1. Sulfamethoxazole is commonly combined with trimethoprim to form a synergistic antimicrobial effect.
2. It works by inhibiting the enzyme dihydropteroate synthase, which is crucial for folate synthesis in bacteria.
3. The combination of sulfamethoxazole and trimethoprim is effective against a broad spectrum of Gram-positive and Gram-negative bacteria.
4. Sulfamethoxazole can be used to treat urinary tract infections, bronchitis, and certain types of diarrhea caused by bacterial infections.
5. Resistance to sulfamethoxazole can occur due to mutations in the target enzyme or increased production of PABA.

Review Questions

• What enzyme does sulfamethoxazole inhibit in bacterial cells?
• Why is sulfamethoxazole often combined with trimethoprim?
• Name two types of infections that can be treated with sulfamethoxazole.

Related terms

Trimethoprim:

An antibiotic that inhibits bacterial dihydrofolate reductase, often used in combination with sulfamethoxazole.

Dihydropteroate Synthase:

An enzyme involved in folate synthesis that is inhibited by sulfonamide antibiotics like sulfamethoxazole.

Para-Aminobenzoic Acid (PABA): A substrate for dihydropteroate synthase, which sulfonamide antibiotics compete with to inhibit folate synthesis.