Which of the following sulfonamides is effective against both gram-positive and gram-negative bacteria?

Sulfonamides are a class of antibiotics that work by inhibiting bacterial folic acid synthesis, which is essential for bacterial growth. The key feature of sulfonamides is their broad-spectrum activity against various types of bacteria. The effectiveness of a particular sulfonamide can depend on various factors, including its pharmacokinetics and the type of bacteria being targeted.

Sulfadiazine, sulfisoxazole, and sulfacetamide are all examples of sulfonamides that possess activity against both gram-positive and gram-negative bacteria. This broad-spectrum coverage makes them useful in treating various bacterial infections.

Sulfadiazine is commonly used in combination with pyrimethamine for the treatment of toxoplasmosis and is effective against both types of bacteria. Sulfisoxazole is often used in urinary tract infections and respiratory infections, showing a similar spectrum of activity. Sulfacetamide is primarily used for ocular infections but also exhibits effectiveness against a variety of bacterial pathogens.

Therefore, stating that all of the mentioned sulfonamides are effective against both gram-positive and gram-negative bacteria reflects their broad-spectrum antibacterial properties, which is why the answer is that all of the listed sulfonamides are indeed effective against both types of bacteria.