Experimental evolution of Pseudomonas aeruginosa in polymicrobial cultures

We used an in vitro model of steady-state polymicrobial communities associated with CF-airway infections to compare how metabolically-active axenic and polymicrobial communities respond to treatment with three clinically-utilised and species-specific antimicrobials compounds. We report a decreased efficacy of all tested antimicrobials against their target pathogen when grown as part of a polymicrobial consortium. This reduced antimicrobial efficacy was found to arise from both protective and inherited mechanisms of resistance. Using whole-genome sequencing, we then identify novel single nucleotide polymorphisms in genes encoding cell surface moieties able to confer complete resistance to colistin in Pseudomonas aeruginosa isolates.