Fluoroquinolones: then and now.

Fluoroquinolones were discovered in the 1960s as a derivative of the antimalarial drug chloroquine. Over the past 40 years, many fluoroquinolones have been developed for use in human and veterinary medicine. As with all classes of antibiotics, resistance to fluoroquinolones is a serious concern, and multiple avenues for resistance are being investigated. Resistance-associated point mutations in bacterial DNA and, more recently, plasmid-mediated resistance have been reported in both human and veterinary bacterial isolates. This article reviews the history and most current literature on fluoroquinolones approved for use in dogs and cats and the spectra of activity, mechanisms of action, resistance patterns, and recommendations for appropriate clinical use of these drugs.