Abstract / Summary
Abstract Background: Klebsiella variicola is a member of the Klebsiella pneumoniae species complex (KpSC) and is frequently misidentified as Klebsiella pneumoniae in routine clinical microbiological testing 1,2 . In recent years, an increasing number of cases of bloodstream infection and pyogenic hepatic abscess caused by this pathogen have been reported; however, to date, no cases of Klebsiella variicola –associated osteomyelitis complicated by multi-site invasive infection have been documented. Case presentation: A 79-year-old woman with long-standing, poorly controlled type 2 diabetes (HbA1c 11.1%) was admitted to the hospital following a fall and presenting with acute right shoulder pain. Shortly after admission, she rapidly developed sepsis that progressed to septic shock complicated by multiple organ dysfunction syndrome (MODS), necessitating transfer to the intensive care unit (ICU); her Sequential Organ Failure Assessment (SOFA) score upon ICU admission was 3. Contrast-enhanced computed tomography (CT) revealed extensive soft-tissue emphysema involving the right shoulder, cervical root, and axilla, as well as intramedullary gas within the right clavicle and scapula. Additional imaging findings included a hepatic abscess and evidence of urinary tract infection. Metagenomic next-generation sequencing (mNGS) of peripheral blood identified Klebsiella variicola (4731 unique reads). Cultures from bone-marrow aspirate, hepatic-abscess pus, and urine recovered isolates of Klebsiella pneumoniae or its species complex. The patient also had concurrent aspiration pneumonia, atrial fibrillation, diabetic ketoacidosis, thrombocytopenia, and hepatic insufficiency. Empiric antimicrobial therapy was initiated with imipenem-cilastatin sodium (500 mg intravenously every 6 hours), later de-escalated to piperacillin-tazobactam (4.5 g intravenously every 8 hours) guided by culture and susceptibility results. Concurrently, percutaneous drainage was performed for both the hepatic abscess and the pleural effusion. Following comprehensive antimicrobial and supportive therapy, her infection gradually resolved, and the patient was subsequently transferred from the intensive care unit (ICU) to a general ward. Conclusion: This case represents the first reported instance of post-traumatic osteomyelitis caused by Klebsiella variicola, complicated by sepsis, hepatic abscess, and urinary tract infection. The causative pathogen exhibits an invasive phenotype resembling that of hypervirulent Klebsiella pneumoniae (hvKp). In patients with diabetes mellitus presenting with severe infection, careful strain-level identification is essential. Bone marrow aspiration and comprehensive microbiological evaluation should be performed promptly; metagenomic next-generation sequencing (mNGS) can facilitate early and accurate pathogen identification. Timely initiation of effective antimicrobial therapy, combined with adequate source control through drainage of infected lesions, is critical to improving patient outcomes.