Exploiting lung adaptation and phage steering to clear pan-resistant Pseudomonas aeruginosa infections in vivo.

Pseudomonas aeruginosa is a major nosocomial pathogen that causes severe disease including sepsis. Carbapenem-resistant P. aeruginosa is recognised by the World Health Organisation as a priority 1 pathogen, with urgent need for new therapeutics. As such, there is renewed interest in using bacteriophages as a therapeutic. However, the dynamics of treating pan-resistant P. aeruginosa with phage in vivo are poorly understood. Using a pan-resistant P. aeruginosa in vivo infection model, phage therapy displays strong therapeutic potential, clearing infection from the blood, kidneys, and spleen. Remaining bacteria in the lungs and liver displays phage resistance due to limiting phage adsorption. Yet, resistance to phage results in re-sensitisation to a wide range of antibiotics. In this work, we use phage steering in vivo, pre-exposing a pan resistant P. aeruginosa infection with a phage cocktail to re-sensitise bacteria to antibiotics, clearing the infection from all organs.

Evolutionary trade-offs associated with loss of PmrB function in host-adapted Pseudomonas aeruginosa.

Pseudomonas aeruginosa colonises the upper airway of cystic fibrosis (CF) patients, providing a reservoir of host-adapted genotypes that subsequently establish chronic lung infection. We previously experimentally-evolved P. aeruginosa in a murine model of respiratory tract infection and observed early-acquired mutations in pmrB, encoding the sensor kinase of a two-component system that promoted establishment and persistence of infection. Here, using proteomics, we show downregulation of proteins involved in LPS biosynthesis, antimicrobial resistance and phenazine production in pmrB mutants, and upregulation of proteins involved in adherence, lysozyme resistance and inhibition of the chloride ion channel CFTR, relative to wild-type strain LESB65. Accordingly, pmrB mutants are susceptible to antibiotic treatment but show enhanced adherence to airway epithelial cells, resistance to lysozyme treatment, and downregulate host CFTR expression. We propose that P. aeruginosa pmrB mutations in CF patients are subject to an evolutionary trade-off, leading to enhanced colonisation potential, CFTR inhibition, and resistance to host defences, but also to increased susceptibility to antibiotics.