Study to Evaluate the Efficacy and Safety of Moxifloxacin Versus Amoxicillin/Clavulanate in the Treatment of Acute Bacterial Rhinosinusitis

Inclusion Criteria: * Age \>= 18 years * Clinical diagnosis of acute rhinosinusitis with signs and symptoms present for \>/= 5-7 days but \< 28 days * Clinical diagnosis will be confirmed by nasal endoscopic examination Exclusion Criteria: * History of chronic sinusitis defined as greater than four weeks of continuous symptoms (subject with history of sinus surgery may be included; subjects with recurrent acute sinusitis may be included) * Any symptoms that suggest the subject's current illness is allergic rhinitis (e.g. repetitive sneezing, itchy nose or eyes, provocation by an allergen) and not acute bacterial sinusitis * Known bacteremia, meningitis or infection infiltrating the tissues neighboring the sinuses * Known immunodeficiency diseases including, but not limited to: neutropenia (neutrophil count \< 1000/mm3), human immunodeficiency virus (HIV) infection (Cluster of differentiation 4 (CD4)+ T-cell count of \< 200/mm3). Note: HIV testing is not required * Received systemic antibacterial therapy likely to be effective in the treatment of acute bacterial sinusitis for more than 24 hours within 5/6 days of enrollment * Requirement for concomitant systemic antibacterial therapy with agents other than those specified in this protocol * Currently receiving topical nasal corticosteroids, unless they have been on a stable dose for \> 4 weeks prior to enrollment * Requirement for concomitant therapy with systemic corticosteroids * Pregnant or breast feeding * Of childbeari…