Iron and Cystic Fibrosis Lung Infections

P. aeruginosa is responsible for life-long and debilitating chronic lung infections in cystic fibrosis (CF) patients. Within the CF lung, P. aeruginosa evolves considerably and becomes increasingly resistant to antibiotic therapy. P. aeruginosa uses a variety of strategies to acquire iron, one of which relies on a small iron-scavenging molecule called pyoverdine. Pyoverdine is required for acute infections, but the ability of some P. aeruginosa strains to make pyoverdine is lost after several years of chronic CF lung infection. We previously showed that heme acquisition is enhanced in CF isolates over time, indicating heme is a more readily available source of iron in the CF lung. Our own studies have shown that antimicrobial activity of P. aeruginosa against Staphylococcus aureus, a common co-colonizer with P. aeruginosa, is enhanced in iron-depleted environments, indicating this “iron piracy” system is responsive to iron availability.