The first generation of quinolones began with the introduction of nalidixic acid in 1962 for treatment of urinary tract infections in humans. Nalidixic acid was discovered by George Lesher and coworkers in a distillate during an attempt at chloroquine synthesis. Quinolones exert their antibacterial effect by preventing bacterial DNA from unwinding and duplicating (please see the Mechanism of Action section for details). The majority of quinolones in clinical use belong to the subset fluoroquinolones, which have a fluorine atom attached to the central ring system, typically at the 6-position or C-7 position.
Fluoroquinolones are broad-spectrum antibiotics (effective for both gram negative and gram positive bacteria) that play an important role in treatment of serious bacterial infections, especially hospital-acquired infections and others in which resistance to older antibacterial classes is suspected. Because the use of broad-spectrum antibiotics encourages the spread of multidrug resistant strains and the development of Clostridium difficile infections, treatment guidelines from the Infectious Disease Society of America, the American Thoracic Society, and other professional organizations recommend minimizing the use of fluoroquinolones and other broad-spectrum antibiotics in less severe infections and in those in which risk factors for multidrug resistance are not present.