This study will evaluate the ability of 4 antibiotics to kill the bacteria that cause tuberculosis (TB). The antibiotics to be studied are linezolid, gatifloxacin, levofloxacin, and moxifloxacin. All are approved by the Brazilian health authorities to treat infections caused by germs other than TB. Seventy human immunodeficiency virus (HIV)-negative adults, aged 18-65 years, who have been newly diagnosed with pulmonary (lung) TB, will participate in this study. Study volunteers will be given one of the 4 study drugs or a comparison antibiotic, Isoniazid, which has been used around the world as a standard of care treatment for TB. Volunteers will stay in the hospital for 10 days and be given a study antibiotic 7 of those days. Blood and saliva samples will be taken. Six weeks later, volunteers will return for a final health check. All volunteers will receive 6 months of standard tuberculosis treatment.