Pseudomonas aeruginosa strains from the chronically infected cystic fibrosis lung display increased invasiveness of A549 epithelial cells over time

► We examined the invasive phenotype of sequential Pseudomonas aeruginosa isolates. ► Identified an increase in invasiveness in later chronic isolates. ► Increase in invasiveness is ExoS-independent. ► Identified a link between invasiveness and clonality.