Gravar-mail: Antimicrobial Activities of Piperacillin-Tazobactam against Haemophilus influenzae Isolates, Including β-Lactamase-Negative Ampicillin-Resistant and β-Lactamase-Positive Amoxicillin- Clavulanate-Resistant Isolates, and Mutations in Their Quinolone Resistance-Determining Regions