Outer Membrane Vesicle and Ferroptosis-Related Signatures in Sepsis-Associated Acute Lung Injury Caused by Extra-Pulmonary Hypervirulent Klebsiella Pneumoniae

This prospective observational translational cohort study will investigate whether extra-pulmonary infection caused by hypervirulent Klebsiella pneumoniae (hvKP) is associated with an increased risk of sepsis-associated acute lung injury (SALI), compared with infection caused by classical Klebsiella pneumoniae (cKP). The study will further examine whether circulating bacterial outer membrane vesicle (OMV) signals and ferroptosis-related biomarker profiles are associated with subsequent SALI development. Adults with Sepsis-3 and microbiologically confirmed extra-pulmonary K. pneumoniae infection will be enrolled within 6 hours of sepsis recognition. Patients with acute lung injury at enrollment will be excluded from the primary cohort. Blood samples will be collected at enrollment, 24 hours, and 72 hours. Clinical isolates will undergo molecular characterization to classify infections as hvKP or cKP. The primary outcome will be new-onset SALI within 7 days after enrollment. A nested translational substudy will evaluate the effects of patient-isolate-derived OMVs on human pulmonary microvascular endothelial cells. The study will not alter antimicrobial therapy, source control, respiratory support, fluid management, or any other aspect of routine clinical care.

Inclusion Criteria: * Age 18-85 years . * Clinical suspicion of infection with acute organ dysfunction consistent with suspected sepsis at the time of enrollment, as determined by the treating clinical team. * Presumed extra-pulmonary source of infection at enrollment, including but not limited to hepatobiliary, urinary, intra-abdominal, skin and soft-tissue, vascular catheter-related, or primary bloodstream infection. * Blood cultures and/or clinically indicated source cultures obtained or ordered as part of routine clinical care. * Enrollment and first research blood collection completed within 6 hours after initiation of the clinical sepsis evaluation. * No evidence of acute lung injury at the index time point, according to the protocol-defined criteria. * Written informed consent obtained from the participant or legally authorized representative, unless an ethics-approved deferred-consent procedure is used. Exclusion Criteria: * Suspected or confirmed primary pulmonary infection at enrollment, including community-acquired pneumonia, hospital-acquired pneumonia, ventilator-associated pneumonia, or aspiration pneumonia. Acute lung injury or acute respiratory distress syndrome present at the index time point. * Acute cardiogenic pulmonary edema, acute decompensated heart failure, or another condition that would preclude reliable adjudication of subsequent non-cardiogenic acute lung injury. * Recent inhalation injury, near-drowning, major thoracic trauma, or transfusion-related acute lung injury. * Previous enrollment in this study. * Inability to obtain informed consent from the participant or legally authorized representative when deferred-consent procedures are not permitted by the local ethics committee.