nalidixic acid
noun
na·li·dix·ic acid ˌnā-lə-ˈdik-sik- 
: an antibacterial agent C12H12N2O3 that is used especially in the treatment of genitourinary infections
Example Sentences
Recent Examples on the Web All of them were resistant to at least seven antibiotics (azithromycin, ciprofloxacin, clindamycin, erythromycin, nalidixic acid, telithromycin, and tetracycline). 
Beth Mole, Ars Technica, 21 Sep. 2018 The outbreak strain of C. jejuni could withstand three antibiotics: tetracycline, nalidixic acid, and ciprofloxacin. Beth Mole, Ars Technica, 11 Feb. 2018
Beth Mole, Ars Technica, 21 Sep. 2018 The outbreak strain of C. jejuni could withstand three antibiotics: tetracycline, nalidixic acid, and ciprofloxacin. Beth Mole, Ars Technica, 11 Feb. 2018 Word History
Etymology
perhaps from naphthyridine (C8H6N2 — from naphth- + pyridine) + carboxylic acid
First Known Use
1962, in the meaning defined above
Medical Definition
nalidixic acid
noun
na·li·dix·ic acid ˌnā-lə-ˌdik-sik-
: an antibacterial agent C12H12N2O3 that is used especially in the treatment of genitourinary infections see neggram