The Fluoroquinolones: An Update for the Clinical Microbiologist

Abstract The fluoroquinolones are a commonly prescribed class of antibiotics with broad activity across a variety of bacteria. As an antimicrobial class, the fluoroquinolones exert antimicrobial activity by direct inhibition of DNA synthesis due to interaction between the fluoroquinolone and two enzymes essential for DNA replication: DNA gyrase and DNA topoisomerase IV. Adverse events and widespread antimicrobial resistance remain two of the major concerns regarding fluoroquinolone use. Resistance can emerge following target site mutations, reduced influx, efflux, target protection, and enzymatic modification of the fluoroquinolones. Recent developments for the fluoroquinolones include revision of susceptibility test breakpoints for Enterobacterales and Pseudomonas aeruginosa, as well as approval of a novel fluoroquinolone, delafloxacin. This review provides an overview of the fluoroquinolones and resistance mechanisms and describes recent developments in susceptibility testing.