Synergistic eradication of NDM-1 Klebsiella pneumoniae biofilm infection by a Meropenem/EDTA Co-delivery system based on gelatin microspheres

New Delhi metallo-β-lactamase (NDM)-producing drug-resistant bacteria often form stubborn biofilms and cause severe pneumonia, resulting in conventional antibiotic failure. In this study, we developed gelatin-genipin microspheres co-loaded with EDTA and meropenem (GEM) for targeted treatment of NDM pneumonia. EDTA exerted dual functions: it chelated Zn 2+ to inactivate NDM enzyme and restore meropenem activity (FIC = 0.046875), while also disrupting bacterial biofilms through chelation. GEM microspheres enable accelerated drug release in the artificial phlegm environment. In a mouse model of NDM pneumonia, GEM microspheres can enhance the recruitment of neutrophils and M1 cells at the early stage (12 h) through bacterial clearance, modulate the secretion of interferon-γ by CD8 + T cells and natural killer cells, and reshape the pulmonary immune microenvironment. Furthermore, GEM treatment reduced pathological pulmonary immune cell infiltration and excessive inflammation at late time points (days 3-7). Taken together, GEM microspheres integrate biofilm disruption, enzyme inhibition, synergistic bactericidal effects, and immunoregulation, representing a promising strategy against NDM drug-resistant bacterial pneumonia.