Clonal strains of Pseudomonas aeruginosa were identified from independent patient-pairs using multilocus sequence typing (MLST). Clonal strains of Pseudomonas aeruginosa were identified from independent patient-pairs using multilocus sequence typing (MLST). Individual strains are coloured by patient. Strain relatedness was assessed using whole-genome sequencing and phylogeny generated from a matrix with the presence and absence of core and accessory genes using Roary [23]. Taylor E. Woo et al. ERJ Open Res 2018;4:00162-2017 ©2018 by European Respiratory Society