Nalidixic acid is used to inhibit gram-positive bacteria in culture medium. This antibiotic has minimal effect on the growth of gram-negative strains. This antibiotic is not active against antibiotic-resistant strains such as tetracycline-resistant strains. Nalidixic acid inhibits DNA synthesis, and also prevents protein synthesis and cell division. Nalidixic acid also has anti-inflammatory effects and is used as a natural compound.