Delafloxacin, an investigational anionic fluoroquinolone, is active against a 
broad range of Gram-positive and Gram-negative bacteria. In this study, 200 
Streptococcus pneumoniae (plus 30 levofloxacin-resistant isolates), 200 
Haemophilus influenzae, and 100 Moraxella catarrhalis isolates selected 
primarily from the United States (2014) were tested against delafloxacin and 
comparator agents. Delafloxacin was the most potent agent tested. MIC50 and 
MIC90 values against all S. pneumoniae isolates were 0.008 and 0.015 μg/ml. 
Delafloxacin susceptibility was not affected by β-lactamase status against H. 
influenzae and M. catarrhalis.