Levofloxacin is a bactericidal antibiotic of the fluoroquinolone drug class that directly inhibits bacterial DNA synthesis. Levofloxacin promotes the breakage of DNA strands by inhibiting DNA-gyrase in susceptible organisms, which inhibits the relaxation of supercoiled DNA. Of the fluoroquinolone class, levofloxacin has the most enhanced activity against gram-positive penicillin-sensitive and resistant organisms, notably Streptococcus pneumoniae and reduced action against gram-negative bacilli, notably Pseudomonas aeruginosa, compared to ciprofloxacin.