Using a liver-on-chip model to evaluate the effects of vancomycin and daptomycin on host immunometabolism and clearance of intracellular reservoirs of Staphylococcus aureus during bacteremia.

Staphylococcus aureus bacteremia (SAB) causes significant morbidity and mortality, despite treatment with guideline-recommended antibiotics. A critical contributor to SAB treatment failure is the intracellular persistence of SA within liver sinusoidal macrophages (Kupffer cells [KCs]). Antibiotics have been shown to modulate immune cell function, which is governed by cellular metabolism; yet, the effect of antibiotics on host immunometabolic response relative to bacterial clearance is understudied. We developed a liver-on-chip (LoC) model of SAB to recapitulate the liver sinusoid during systemic infection using exclusively liver-derived cells and the GFP USA300 LAC SA strain and compared the effects of vancomycin and daptomycin on host immunometabolism by fluorescence lifetime imaging microscopy and related to intracellular antimicrobial efficacy. Utilizing both murine and human-based LoC infection models, we found that DAP was superior to VAN treatment in clearing intracellular SA from the liver microenvironment, which corresponded to differential host immunometabolic responses. DAP showed low NAD(P)H fluorescence lifetime and low mitochondrial ROS, suggestive of a redox-buffered state that balanced pathogen containment with hepatic metabolic homeostasis, while VAN treatment biased towards greater utilization of OXPHOS. Our findings using a novel in vitro microphysiological system mimicking the liver tissue microenvironment offer insights into antibiotic-mediated bacterial clearance that accounts for host immunometabolism beyond direct antimicrobial activity.