Mechanisms of antibiotic tolerance in hypervirulent Klebsiella pneumoniae infections

Hypervirulent Klebsiella pneumoniae (hvKp) is an increasingly important cause of severe community-acquired infections, including pyogenic liver abscesses that frequently lead to bacteremia, metastatic disease, and death. Although hvKp is often reported as susceptible to frontline β-lactam antibiotics, clinical treatment failure is common, revealing a critical disconnect between antimicrobial susceptibility testing and patient outcomes. This gap is particularly pronounced in individuals with diabetes, yet the biological basis for hvKp antibiotic failure remains poorly understood. Using a clinically relevant liver abscess model and spatially resolved drug imaging, we discovered that β-lactam antibiotics penetrate hvKp abscesses at therapeutic concentrations but fail to eradicate bacteria, demonstrating that hvKp survives therapy through antibiotic tolerance rather than resistance. Our preliminary data indicate that this tolerance emerges from interactions between bacterial virulence programs and host-imposed constraints within infected tissue. Host nutritional immunity restricts iron availability in the liver, creating a microenvironment that diminishes β-lactam killing, while the hypermucoviscous capsule characteristic of hvKp further limits antibiotic efficacy without altering standard susceptibility measurements. These tolerance mechanisms are predicted to be amplified in diabetic hosts, where iron handling is dysregulated. This project will define how host iron restriction and bacterial capsule production shape antibiotic tolerance during hvKp liver infection and determine how these processes undermine β-lactam efficacy in vivo. By integrating in vivo infection models, host-pathogen transcriptomics, bacterial genetics, and spatial drug distribution analyses, this work will establish a mechanistic framework for hvKp treatment failure that extends beyond classical resistance paradigms. The expected outcome of this research is a shift in how hvKp antibiotic failure is understood and addressed. These studies will inform treatment strategies including improved deployment of iron-responsive antibiotics and development of adjunctive approaches that enhance drug activity within restrictive host environments, ultimately improving outcomes for serious bacterial infections.