Deciphering the impact of sedative choice on the dynamics of Klebsiella pneumoniae lung infection

Summary Healthcare-associated infections adversely impact patient outcomes and increase healthcare costs by billions of dollars each year. Anesthetic administration is associated with a significantly increased risk of infection via its alterations of immune signaling and immune effector cell function. Despite the increasing recognition that anesthetics modulate immunity, relatively little remains known regarding the breadth of mechanisms by which drugs that target the nervous system influence host immune responses. We have previously demonstrated that brief sedation with propofol, the most commonly used drug for anesthetic induction, dramatically increases host susceptibility to microbial infection. Propofol is widely used for patients requiring intubation and mechanical ventilation, and patients in the ICU can remain sedated with propofol for days. To better define the impact of propofol sedation on respiratory disease, we have developed a mouse model of lung infection using the Gram- negative opportunistic pathogen Klebsiella pneumoniae (Kp). Kp is a growing threat worldwide as a nosocomial pathogen due to its rapid acquisition of antimicrobial resistance; in addition, hypervirulent strains causing community-acquired infections have been recently reported. Preliminary experiments indicate that propofol sedation dramatically increases the severity of Kp disease pathology within the lungs and promotes bacterial dissemination to distal tissues. Using transposon insertion sequencing (INSeq) and libraries of Kp insertion mutants, we have further demonstrated that the choice of sedative influences the selection of Kp mutants that are defective for growth within the infected lung. These results strongly suggest that propofol not only influences the pathology and outcome of lung infection, but that it also differentially impacts the arsenal of bacterial virulence factors required for disease. This proposal is thus designed to explore two related and mutually important hypotheses, those being (1) that propofol increases host susceptibility to microbial (Kp) infection in the lung via alterations in immune signaling that interfere with the recruitment and function of innate immune effector cells; and (2) the choice of sedation alters the lung environment in ways that impact the Kp global virulence repertoire required for bacterial growth in tissues. Aim 1 experiments will determine how sedation choice influences the outcome and progression of Kp lung infection in vivo. Aim 2 will functionally characterize Kp mutants identified based on their virulence being differentially impacted by sedation with propofol versus ketamine/xylazine. Overall, these experiments will provide valuable and important information regarding the impact of sedation on respiratory infection outcome and prognosis.