Pathoadaptive isolates of Pseudomonas aeruginosa. Pseudomonas aeruginosa

The chronic colonisation of the respiratory tract by the opportunistic pathogen Pseudomonas aeruginosa is the primary cause of morbidity and mortality in Cystic Fibrosis (CF) patients. P. aeruginosa has been shown to undergo extensive genomic adaptation facilitating its persistence within the CF lung allowing it to evade the host immune response and outcompete co-colonisers within the lung microbiota. However, whilst several studies describe the mutations that frequently arise in clinical isolates of P. aeruginosa, the environmental factors governing the emergence of these genetic variants is less well characterised. Bile aspiration, a consequence of gastro-oesophageal reflux, has recently emerged as a major co-morbidity in CF. In order to investigate whether bile may select for genetic variants, P. aeruginosa was experimentally evolved in Artificial Sputum Medium, a synthetic media resembling environmental conditions found within the CF lung. Pigmented derivatives of P. aeruginosa emerged exclusively in the presence of bile with genome sequencing analysis identifying single nucleotide polymorphisms (SNPs) in quorum sensing (lasR) and both the pyocyanin (phzS) and pyomelanin (hmgA) pathways.