RDP Pilot: Mechanisms and fitness of spontaneous aztreonam resistance in Pseudomonas aeruginosa

P.I.: Stephen Salipante, MD, PhD
Assistant Professor, Laboratory Medicine

This proposal aims to investigate the mechanisms of spontaneous aztreonam resistance in Pseudomonas aeruginosa, a major bacterial pathogen in CF. Aztreonam is a relatively new inhaled antibiotic used to treat CF patients, yet the potential for aztreonam resistant P. aeruginosa to arise through spontaneous mutations is currently unknown, and may represent a significant threat to the efficacy of that antibiotic in clinical use. Using a paradigm of experimental evolution and whole genome sequencing, we aim to catalog the mutations capable of conferring increased resistance to aztreonam, and to explore their effects on bacterial fitness in patient airways.

In the first year, we performed experimental selection studies and whole genome characterization of evolved P. aeruginosa isolates in order to identify recurrent genomic lesions which are associated with aztreonam resistance. We validated the effects of many of these mutations experimentally, and have additionally characterized the mutations occurring in CF clinical isolates with an aztreonam resistance phenotype.

In the second year, we have explored the secondary consequences of aztreonam resistance causing mutations on bacterial fitness, resistance to other antibiotics, and pathogenicity in mammalian hosts.