This is a randomized, open-label, single center, exploratory, Phase 1 study to explore changes and resistance patterns of bacteria in the oral flora of healthy male and female adult subjects. The study is to enroll approximately 140 healthy subjects. Approximately 70 subjects are to receive levofloxacin once daily for 5 days and 70 are to receive azithromycin once daily for 5 days. Male or female healthy subjects, 18 years or older may participate. Subjects will be treated on an outpatient basis at a Phase 1 facility. Laboratory testing (blood and urine collection) and microbiologic testing (throat swab) will be performed before dosing with study drug at the Study Entry (Visit 1). Subjects will return daily to the testing facility for their once-daily dosing of study drug for Visits 2 through 5 for a total of 5 consecutive days. At Visit 5 laboratory and microbiologic testing will be performed. Subjects will again return to the testing facility for the 2-Week (Visit 6), 4-Week (Visit 7) and 6-Week (Visit 8) Post-Therapy Visits to undergo microbiologic testing (throat swab). The primary endpoint is the emergence of bacterial resistance in the oropharyngeal flora starting prior to the initiation of study drug through a 6-week observation period. Microbiologic testing (throat swab) will be conducted prior to dosing on Day 1 and following dosing on Days 5, 19, 33, and 47. Safety assessments will be conducted prior to drug administration, during study drug treatment, and at the end-of-therapy visit. These included clinical laboratory evaluations, vital signs, physical examinations, pregnancy testing, and collection of adverse events. Serious adverse events will be collected for 30 days following the last dose of study drug. Levofloxacin Once-Daily 750 mg PO For 5 Days And Azithromycin Once-Daily 500 mg PO On Day One And Then 250 mg On Days 2 Through 5