Fluoroquinolone
Fluoroquinolones are synthetic antibiotics that inhibit bacterial DNA gyrase and topoisomerase IV, enzymes needed to copy and maintain bacterial DNA.
DNA gyrase: A bacterial type II topoisomerase that relieves DNA supercoiling during replication and transcription. Fluoroquinolones stabilize its DNA-cleavage complex, blocking replication and damaging chromosomes.
Ciprofloxacin: A fluoroquinolone antibiotic with strong activity against many Gram-negative bacteria, including Pseudomonas aeruginosa. It is a widely used example, particularly for selected urinary, gastrointestinal, and serious Gram-negative infections.
Quinolone: A family of synthetic compounds built around a bicyclic nitrogen-containing ring system. Fluoroquinolones are quinolones modified with a fluorine atom and other substitutions.
Beta-lactam: An antibiotic class that inhibits bacterial cell-wall synthesis by binding penicillin-binding proteins. Beta-lactams attack cell-wall construction rather than DNA topology.
Topoisomerase IV: A bacterial type II topoisomerase that separates interlinked daughter chromosomes after DNA replication. It is the other principal fluoroquinolone target, especially in many Gram-positive bacteria.
Levofloxacin: A fluoroquinolone antibiotic used for selected respiratory, urinary, and other bacterial infections. Its spectrum and tissue distribution illustrate uses that differ from ciprofloxacin's.
Type II topoisomerase: An enzyme that cuts both strands of one DNA segment to pass another DNA segment through it. Both principal bacterial targets belong to this enzyme family.
Macrolide: An antibiotic class that inhibits bacterial protein synthesis by binding the 50S ribosomal subunit. Macrolides target translation, a distinct process from the DNA enzymes inhibited by fluoroquinolones.
Quinolone resistance: Reduced bacterial susceptibility to quinolone antibiotics through target changes, drug exclusion, or drug inactivation. Mutations in target enzymes and other defenses can make fluoroquinolones less effective.
Moxifloxacin: A fluoroquinolone with activity against respiratory pathogens and anaerobes, but limited urinary excretion. Its properties show why drugs within the class are not interchangeable.