Inclusion Criteria:

• Outpatients
• Male or female subjects, >/=60 years old
• Subject who can be managed with oral antimicrobials
• FEV1>/=50% predicted at enrollment in addition to a historical record of FEV1 of >/=60% within the past 12 months obtained during a stable infection-free period. A historical record of FEV1 is not required if the enrollment FEV1 is >/=50%.
• Documented history of 2 or more AECB episodes, within 12 months of study enrollment, requiring a course of systemic antibiotics and/or systemic corticosteroids

• All symptoms/signs must be present and confirmed by the Investigator:

  • Increase in dyspnea
  • Purulent sputum
  • Increase in sputum volume
• Subject must provide a purulent sputum sample by deep expectoration prior to randomization for Gram stain, culture and sensitivity testing. The sputum will be assessed macroscopically by the investigator and graded according to the provided color chart.
• Current or past cigarette smoker with >/=20 pack year smoking history
• Subjects must have an infection-free interval of at least 30 days prior to enrollment
• Subjects must be willing and able to complete the questionnaires and subject booklet without assistance
• Subjects with medical conditions and social status at the time of enrollment compatible with study protocol procedures
• Willing and able to provide written informed consent

Exclusion Criteria:

• Known hypersensitivity to quinolones, ß-lactams, or to any of the excipients of the study drugs
• Known to have congenital or acquired QT prolongation
• Known to have clinically relevant bradycardia
• Known to have clinically relevant heart failure with reduced left ventricular ejection fraction
• Known to have previous history of symptomatic arrhythmias
• Taking QT prolonging drugs
• Known electrolyte disturbances that are not controlled, particularly uncorrected hypokalemia
• Known history of hereditary problems of galactose intolerance, the Lapp lactase deficiency, or glucose galactose malabsorption
• Requiring hemodialysis
• History of a tendon disease/disorder
• Known history of liver dysfunction, including known elevated transaminases (ALT and/or AST >3 times the upper limit of normal)
• Known severe renal impairment with glomerular filtration rate of <30mL/min
• Known neutropenia (neutrophil count <1000/mm3) caused by immunosuppressive therapy or malignancy
• Known to have AIDS (CD4 count of <200/mm3), or be HIV positive and receiving Highly Active Anti Retroviral Therapy (HAART) (HIV testing is not mandatory)
• Known bronchial carcinoma, active pulmonary tuberculosis, known diffuse bronchiectasis, cystic fibrosis, chronic asthma (>15% reversibility), or pneumonia (a chest X ray is not mandatory)
• Known history of chronic colonization of pathogenic organisms resistant to moxifloxacin and/or amoxicillin clavulanic acid (e.g., Pseudomonas aeruginosa, MRSA)
• Receiving long term (>4 consecutive weeks) systemic corticosteroid treatment (>10 mg/day of prednisolone or equivalent)
• Received short course of systemic corticosteroid treatment within 30 days prior to enrollment
• Requiring intravenous antibiotic therapy for treatment of the current exacerbation
• Unable to take oral medication
• Life expectancy of less than 6 months
• Receiving systemic antibacterial therapy within 30 days prior to study enrollment
• Requiring concomitant systemic antibacterial agents
• Use of any investigational drug or device within 30 days of screening, or previously enrolled in this study
• Requiring home ventilatory support (subjects requiring home/portable oxygen therapy or CPAP for sleep apnea are not excluded) and/or those who have a tracheotomy in situ