nalidixic acid CHEBI:7456 A monocarboxylic acid comprising 1,8-naphthyridin-4-one substituted by carboxylic acid, ethyl and methyl groups at positions 3, 1, and 7, respectively. An orally administered antibacterial, it is used in the treatment of lower urinary-tract infections due to Gram-negative bacteria, including the majority of <em>E. coli</em>, <em>Enterobacter</em>, <em>Klebsiella</em>, and <em>Proteus</em> species. monocarboxylic acid 1,8-naphthyridine derivative quinolone antibiotic