Epidemiology, Biology, and Impact of Clonal Pseudomonas aeruginosa Infections in Cystic Fibrosis

Chronic lower airway infection with <i>Pseudomonas aeruginosa</i> is a major contributor to morbidity and mortality in individuals suffering from the genetic disease cystic fibrosis (CF). Whereas it was long presumed that each patient independently acquired unique strains of <i>P. aeruginosa</i> present in their living environment, multiple studies have since demonstrated that shared strains of <i>P. aeruginosa</i> exist among individuals with CF. Many of these shared strains, often referred to as clonal or epidemic strains, can be transmitted from one CF individual to another, potentially reaching epidemic status. Numerous epidemic <i>P. aeruginosa</i> strains have been described from different parts of the world and are often associated with an antibiotic-resistant phenotype. Importantly, infection with these strains often portends a worse prognosis than for infection with nonclonal strains, including an increased pulmonary exacerbation rate, exaggerated lung function decline, and progression to end-stage lung disease. This review describes the global epidemiology of clonal <i>P. aeruginosa</i> strains in CF and summarizes the current literature regarding the underlying biology and clinical impact of globally important CF clones. Mechanisms associated with patient-to-patient transmission are discussed, and best-evidence practices to prevent infections are highlighted. Preventing new infections with epidemic <i>P. aeruginosa</i> strains is of paramount importance in mitigating CF disease progression.