Besifloxacin HCl is a fourth-generation fluoroquinolone antibiotic.

In vitro: Besifloxacin is a novel 8-chloro-fluoroquinolone agent with potent, bactericidal activity against prevalent and drug-resistant pathogens.besifloxacin is the most potent agent tested against gram-positive pathogens and anaerobes and is generally equivalent to comparator fluoroquinolones in activity against most gram-negative pathogens. Besifloxacin demonstrates potent, broad-spectrum activity, which is particularly notable against gram-positive and gram-negative isolates that are resistant to other fluoroquinolones and classes of antibacterial agents.