Description: Delafloxacin, also known as ABT-492, RX-3341 and WQ-3034, is a non-zwitterionic fluoroquinolone antibiotic under development for for the treatment of respiratory and skin infections. Delafloxacin demonstrates excellent antibacterial potency and exhibits a low probability for the selection of resistant mutants in MRSA. Although mutants can be selected at low frequencies in vitro from quinolone-resistant isolates, delafloxacin MICs and MPCs remain low and a fitness cost can be observed. Consequently delafloxacin warrants further investigation for the potential treatment of drug-resistant MRSA infections.