The combined activity of trimethoprim-sulfonamide as a result inhibits two successive steps in the folic acid pathway, producing a bactericidal effect.

Is trimethoprim sulfamethoxazole bacteriostatic?

When used alone, these drugs only act in a bacteriostatic manner. However, when used in the combination of sulfamethoxazole-trimethoprim, they block two steps in the bacterial biosynthesis of essential nucleic acids and proteins, thus can be bactericidal e.g., urine.

Is septrin bactericidal or bacteriostatic?

When used alone, trimethoprim is bacteriostatic, but it is bactericidal when combined with sulfonamides. Trimethoprim is used in combination with sulfonamides to treat urinary tract infections, prostatic infections, otitis media in children, elimination of Shigella, and treatment of Pneumocystis carinii pneumonia.