Mechanisms of Pseudomonas aeruginosa adaptation, colonization, and host responses in children with artificial airways

This proposal presents a five-year research career development program studying Pseudomonas aeruginosa evolution and phenotypic adaptations in patients with tracheostomy tubes (TT) and host responses that promote airway colonization leading to ventilator-associated infections (VAI). The candidate, Glenn J. Rapsinski, MD, PhD, is an Instructor of Pediatric Infectious Diseases at UPMC Children’s Hospital of Pittsburgh and the University of Pittsburgh School of Medicine. The proposal augments the candidate’s research skills and clinical experience in host-pathogen interactions by incorporating two new disciplines: bacterial evolution and epithelial cell biology. The proposed studies and multifaceted training plan incorporate course work, immersive training, and one-on-one mentorship to provide a skillset and interdisciplinary perspective empowering his transition to an independent physician scientist studying bacterial adaptations and host-pathogen interactions during device infections. VAI, such as pneumonia and tracheitis, are a common complication of mechanical ventilation. Ventilator-associated pneumonia alone costs ~$2.5 billion per year in the US. Children with TT comprise most incidents of pediatric VAI. In most cases, previously colonizing organisms invade to cause acute infection of the trachea or lungs. P. aeruginosa is the most common cause of VAI and adapts during other chronic airway colonization. However, adaptations of TT colonizers and how these genetic or metabolic changes alter pathogenic potential and host responses are unknown. My preliminary data suggest that P. aeruginosa reduces acute virulence during TT airway colonization, airway epithelial function is altered by having a TT, and that the host responds differently to adapted P. aeruginosa. The proposed Specific Aims are: (1) to define P. aeruginosa diversity, persistence, and evolution in patients during TT colonization; (2) to determine TT-airway environmental factors driving early P. aeruginosa airway adaption; and (3) to delineate host responses to TT- adapted P. aeruginosa strains. I will define P. aeruginosa diversity and persistence using whole genome sequencing of P. aeruginosa isolates obtained from patients with TT and adaptations will be identified among variants within longitudinal isolates. I will also use an in vitro bacterial evolution model with media chemically similar the human lung to determine the selective pressures in the host nutritional environment with and without the TT surface. The effects of putative adaptations on host responses will be quantified using a specialized in vitro primary lung epithelial cell and animal infection models. The proposal pioneers research into P. aeruginosa evolution during TT colonization and host responses to adapted strains. The long-term goal is to discover specific bacterial mutations and mutated pathways, and mechanisms of host colonization for novel therapeutics that will be applicable to other medical device-associated infections.