One bacterium can reproduce into over 2 million in 7 hours. Quinolones are synthetic antimicrobials active against gram-negative bacteria. Nalidixic acid was the first quinolone developed in the 1960s, while later fluoroquinolones in the 1980s were more potent and had broader spectra. Fluoroquinolones work by inhibiting bacterial DNA gyrase and topoisomerase IV, and are generally well-absorbed with few resistance issues. Common uses include urinary tract infections and respiratory, gastrointestinal, and skin infections. Adverse effects can include nausea, tendon damage, and interactions with other drugs.