Inter-strain interactions in opportunistic pathogen aid survival under antibiotic selection

Many infections are polymicrobial in nature. In such infections, ecological aspects such as microbial interactions, horizontal gene transfer, standing genetic variation, and spatial structure can act as drivers of antimicrobial resistance (AMR). Past work on resistance evolution in polymicrobial infections relies on observational data collected from patients, making it difficult to infer cause and effect. Further, the few experimental studies that focus on ecological drivers of AMR ignore the variation in a single species. In this study, we wanted to investigate the contribution of these factors to antibiotic resistance evolution in a mixed-strain population of the opportunistic pathogen Pseudomonas aeruginosa. The findings from this study further the understanding of microbial interactions and their effect on evolution. They also highlight the necessity of considering the ecological aspects of infecting populations during antibacterial therapy.