Nalidixic acid (tradenames Nevigramon, Neggram, Wintomylon and WIN 18,320) is the first of the synthetic quinolone antibiotics. In the technical sense, it is a naphthyridone, not a quinolone: its ring structure is a 1,8-naphthyridines nucleus that contains two nitrogen atoms, unlike quinoline, which has a single nitrogen atom.
Synthetic quinolone antibiotics were discovered by George Lesher and coworkers as a byproduct of chloroquine manufacture in the 1960s.
Nalidixic acid is effective against both gram-positive and gram-negative bacteria. In lower concentrations, it acts in a bacteriostatic manner; that is, it inhibits growth and reproduction. In higher concentrations, it is bactericidal, meaning that it kills bacteria instead of merely inhibiting their growth.
It is especially used in treating urinary tract infections, caused, for example, by Escherichia coli, Proteus, Shigella, Enterobacter, and Klebsiella.
It is also a tool in studies as a regulation of bacterial division. It selectively and reversibly blocks DNA replication in susceptible bacteria. Nalidixic acid and related antibiotics inhibit a subunit of DNA gyrase and induce formation of relaxation complex analogue. It also inhibits the nicking dosing activity on the subunit of DNA gyrase that releases the positive binding stress on the supercoiled DNA. It is the only FDA approved quinolone for treating UTI infections in children.
Read more about Nalidixic Acid: Adverse Effects, Spectrum of Bacterial Susceptibility and Resistance