Investigator: Matthew Ramsey, University of Rhode Island
Mentor: David Nelson, University of Rhode Island
Scientific Theme: Molecular Toxicology
Abstract: Kingella kingae is an emerging pathogen in pediatric infectious diseases that colonizes the throat (oropharynx) of 3-17% of children ~6-60 months asymptomatically and infrequently disseminates from the oropharynx to cause endocardial (heart) or osteoarticular/ osteomyelitic (joint and bone) infection. Outbreaks of invasive K. kingae infection have been observed in child ‘daycare’ centers. The oropharynx environment is colonized by numerous bacterial species and their impact on colonization and virulence of other pathogens in this environment has been studied with some detail. Yet, the impact of these bacteria on K. kingae is unknown. Recent work has shown that surface pili are needed for full adherence to epithelial cells during K. kingae colonization and that a single toxin is required for virulence in animal models. However, the regulation of the K. kingae toxin has not been investigated and the full extent of surface pili regulation also requires further study. Previously, we demonstrated that other oral and nasopharyngeal pathogens are significantly impacted in virulence and colonization ability by interactions with native microbes in the human microbiome. Our global hypothesis is that interacting members of the oropharyngeal microbiota modulate gene expression key to colonization or invasive infection in K. kingae, potentially including RTX toxin and type IV pili expression. Aim 1 will identify regulators of pili and toxin expression by generating reporter strains for expression of these factors and quantifying reporter activity in a library of insertionally inactivated gene mutants. We will also quantify reporter activity in the presence of abundant oropharynx microbes and will delete known regulatory elements for pili and toxin expression and determine their contribution to regulation of other factors potentially involved in virulence via RNASeq analysis. Aim 2 will identify mutants that have diminished attachment to human epithelial cells and also mutants that have diminished survival in human serum, necessary requirements for colonization and invasive infection. These data will fully characterize pili and toxin gene regulation in K. kingae and how the native oropharynx microbiota impact colonization and virulence in this emerging pathogen.
Human Health Relevance: This proposal examines the impact of healthy microbes colonizing the throat on the pediatric infectious disease causing pathogen Kingella kingae. How this pathogen transitions from an asymptomatic colonizer to infectious organism is unknown. Our proposal will identify ways that regulation of known virulence factors are needed for this transition and will determine if adjacent microbes prevent or help cause K. kingae infection.