Mechanisms of ciprofloxacin resistance in Pseudomonas aeruginosa: new approaches to an old problem

The antibiotic ciprofloxacin is used extensively to treat a wide range of infections caused by the opportunistic pathogen Pseudomonas aeruginosa. Due to its extensive use, the proportion of ciprofloxacin-resistant P. aeruginosa isolates is rapidly increasing. Ciprofloxacin resistance can arise through the acquisition of mutations in genes encoding the target proteins of ciprofloxacin and regulators of efflux pumps, which leads to overexpression of these pumps. However, understanding of the basis of ciprofloxacin resistance is not yet complete. Recent advances using high-throughput screens and experimental evolution combined with whole-genome sequencing and protein analysis are enhancing our understanding of the genetic and biochemical mechanisms involved in ciprofloxacin resistance. Better insights into the mechanisms of ciprofloxacin resistance may facilitate the development of new or improved therapeutic regimes effective against P. aeruginosa. In this review we discuss the current understanding of the mechanisms of ciprofloxacin resistance and summarize the genetic basis of ciprofloxacin resistance in P. aeruginosa, in the context of current and future use of this antibiotic.