Fluoroquinolones are a family of synthetic broad-spectrum antibacterial drugs.
Fluoroquinolones function by inhibiting two enzymes essential for bacterial cellular replication: DNA gyrase and Topoisomerase IV.
DNA gyrase catalyzes the negative supercoiling of the circular DNA found in bacteria and Topoisomerase IV, on the other hand, is involved in the separation process of the DNA daughter chains after bacterial DNA duplication. Depending on the type of bacterium, these enzymes represent either the primary or secondary target of Fluoroquinolones action.
In Gram-negative bacteria, such as E.coli, fluoroquinolones predominantly inhibit DNA gyrase, whereas for Gram-positive organisms like Staph.aureus, Topoisomerase IV is the principle target.
Ultimately, the action of Fluoroquinolones on DNA gyrase or on topoisomerase IV, results in damage to bacterial DNA and bacterial cell death.